A Practical Guide to Clinical Virology

Second Edition

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

A Practical Guide to Clinical Virology

Second Edition

Edited by

L. R. Haaheim

Professor ofMedical Microbiology, Department ofMicrobiology and

Immunology, Universityof Bergen, Bergen, Norway

J. R. Pattison

Director ofResearch, Analysis and Information,Department of Health,

London, UK

R. J. Whitley

Department ofPediatrics, The Children’s Hospital,

The Universityof Alabama at Birmingham,

Birmingham, USA

WestSussex PO198SQ, England

Telephone(+44) 1243779777

Firstedition published1989

ReprintedFebruary 1993,November 1994

Thisbook isbased onHa

ndboki KliniskVirologi editedby

GunnarHaukenes andLars R.Haahe im,1983.

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CONTENTS

Contributors ix

Preface xi

Preface to1st Edition xiii

Abbreviations xv

References forFurther Reading xvii

1 Classiﬁcation andNomenclature of Human andAnimal Viruses

Y. Ghendon 1

2 Viruses andDisease

G. Haukenesand J. R. Pattison 7

3 Laboratory Diagnosisof Virus Infections

G. Haukenesand R. J. Whitley 15

4 Antiviral Drugs

J. S.Oxford and R. J.Whitley 21

5 Virus Vaccines

L. R.Haaheim and J. R.Pattison 37

6 Enteroviruses: Polioviruses,Coxsackieviruses, Echoviruses

and NewerEnteroviruses

A.-L. Bruu 45

7 Polioviruses

A.-L. Bruu 47

8 Coxsackieviruses, Echovirusesand Enteroviruses 29–34 and68–71

A.-L. Bruu 55

9 Rhinoviruses andCoronaviruses

I. Ørstavik 61

10 Inﬂuenzaviruses

L. R.Haaheim 67

11 Parainﬂuenzaviruses

A. B.Dalen 75

12 Mumps Virus

B. Bjorvatnand G. Haukenes 81

13 Respiratory SyncytialVirus (RSV)

G. A

nestad 89

14 Measles Virus

N. A.Halsey 97

15 Rubella Virus

G. Haukenes 105

16 Adenoviruses

I. Ørstavikand D. Wiger 113

17 Rotaviruses

I. Ørstavikand E. Kjeldsberg 121

18 Herpes SimplexVirus (HSV1 and HSV2)

E. Tjøttaand G. Hoddevik 127

19 Varicella-Zoster Virus(VZV)—Varicella

A. Winsnesand R. Winsnes 137

20 Varicella-Zoster Virus(VZV)—Zoster

A. Winsnesand R. Winsnes 145

21 Cytomegalovirus (CMV)

A. B.Dalen 149

22 Epstein–Barr Virus(EBV)

E. Tjøtta 157

23 Human Herpesvirus6 (HHV-6)

J. A.McCullers 167

24 Hepatitis AVirus

M. Degre

173

25 Hepatitis BVirus

G. L.Davis 179

26 Hepatitis CVirus

G. L.Davis 185

27 Hepatitis DVirus

G. L.Davis 191

28 Hepatitis EVirus

M. Degre

195

29 Emerging HepatitisViruses

G. L.Davis 201

30 Parvovirus B19

J. R.Pattison 203

31 Retroviruses

A. B.Dalen 209

32 Human ImmunodeﬁciencyVirus (HIV)

B. A

sjo

213

33 Human T-CellLymphotropic Virus Type Iand II

R. J.Whitley and G. Shaw 221

34 Tick-borne Encephalitis(TBE) Virus

T. Traavik 227

35 Hantaviruses—HFRS andHPS

D. Wiger 235

36 Haemorrhagic FeverViruses

G. Haukenes 241

37 Rabies Virus

B. Bjorvatnand G. Haukenes 245

38 Human Papillomavirus(HPV)

T. Traavik 251

39 Human Polyomaviruses

T. Traavik 259

40 Slow Viruses

G. Haukenes 263

41 Poxviruses

G. Haukenes 267

42 Clinical Syndromes

G. Haukenesand J. R. Pattison 271

Index 277

vii

THE TYPINGPOOL

CONTRIBUTORS

Dr Gabriel A

nestad, Department of Virology, National Institute of Public

Health, Geitmyrsveien75, N-0462 Oslo, Norway

Professor Birgitta A

sjo

, Centre for Research in Virology, Department of

Microbiology and Immunology,The Gade Institute, University ofBergen,

PO Box7800, N-5020 Bergen, Norway

Tel: +47 55 58 45 08; Fax: +47 55 58 45 12; E-mail: birgitta.asjo@

vir.uib.no

Professor Bjarne Bjorvat n, Centre for International Health, University of

Bergen, Armauer Hansen’sBuilding, Haukeland Hospital, N-5021 Bergen,

Norway

E-mail: bjarne.bjorvatn@cih.uib.no

Dr Anne-Lise Bruu, Mikrobiologisk laboratorium, Sykehuset: Vestfold HF,

Postboks 2168,Postterminalen, 3103, Tønsberg, Norway

Professor Are B. Dalen, Institute of Cancer Research, University of

Trondheim, MedisinskTeknisk Centre, Norway

Tel: +47 22 04 22 86; Fax: +47 22 04 24 47; E-mail: gabriel.anestad@

folkehelsa.no

GaryL. DavisM.D., Director,Division ofHepatology, MedicalDirector, Liver

Transplantation, BaylorUniversity Medical Center, Dallas,Texas, USA

Professor Miklos Degre

, Institute of Medical Microbiology, Rikshospitalet

University Hospital,0027 Oslo, Norway

Tel: +4723 0711 00; Fax:+47 23 0711 10; E-mail:degre@labmed.uio.no

Dr Yuri Ghendon, ResearchInstitute for Viral Preparations, 1 Dubrovskaya

Street 15,109088 Moscow, Russian Federation

Fax: 7095 274 5710

Professor Lars R. Haaheim, Departmentof Microbiology and Immunology,

University of Bergen,Bergen High Technology Centre,POB 7800, N-5020

Bergen, Norway

E-mail: lars.haaheim@gades.uib.no

Dr Neil A. Halsey, Johns Hopkins University, Departmentof International

Health, 615N Wolfe Street, Baltimore,MD 21205-2103, USA

Professor Gunnar Haukenes, Centre for Research in Virology, Bergen High

Technology Centre, University of Bergen, PO Box 7800, N-5020 Bergen,

Norway

E-mail: gunnar.haukenes@vir.uib.no

Dr Gunnar Hoddevik, Department of Virology, National Institute ofPublic

Health, Geitmyrsveien75, N-0462 Oslo, Norway

Dr ElisabethKjeldsberg, Prof Dahls gate47, N-0367 Oslo, Norway

Dr Jonathan A. McCullers, Department of Infectious Diseases, St Jude

Children’s Research Hospital, 332 N Lauderdale Street, Memphis,

TN 38105-2794,USA

Tel:+1901 4955164; Fax:+1901495 3099;E-mail: jon.mccullers@stjude.org

Dr Ivar Ørstavik, Chief Medical Ofﬁcer, Division of Infectious Disease

Control, NorwegianInstitute of PublicHealth, P.O. Box4404 Nydalen, N-

0403 Oslo,Norway

Tel: +4722 04 22 85;Fax: +47 2204 24 47

E-mail: ivar.orstavik@folkehelsa.no

Professor John S. Oxford, Academic Virology, Department of Medical

Microbiology, StBartholomew’s andthe Royal LondonSchool ofMedicine

and Dentistry,Turner Street, Whitechapel, LondonE1 2AD, UK

Tel: +44(0)207 375 2498

Professor Sir John R. Pattison, Director of Research, Analysis and

Information, Department of Health, Richmond House, 79 Whitehall,

London SW1A2NS, UK

E-mail: john.pattison@doh.gsi.go.uk

Dr GeorgeShaw, The University ofAlabama at Birmingham, Departmentof

Medicine, Birmingham,AL 35294, USA

DrEnok Tjøtta, Micro-InventAS, Høyenhallsvingen23, N-0667Oslo, Norway

Tel: +4722 26 54 90

Professor TerjeTraavik, Instituteof MedicalBiology, Departmentof Virology,

N-9037 Universityof Tromsø, Norway

Professor Richard J. Whitley, The University of Alabama at Birmingham,

Department ofPediatrics, TheChildren’s Hospital AmbulatoryCare Center

616, 16007th Avenue South, Birmingham,AL 35294-0011, USA

Tel: 001 205 934 5316; Fax: 001 205 934 8559; E-mail: r.whitley@peds.

uab.edu

Donna Wiger, MSc,The Norwegian Medicines Agency, Sven Oftedals vei6,

N-0950 Oslo, Norway

E-mail: Donna.Wiger@legemiddelverket.no

Drs Randiand ArntWinsnes, TheNorwegian MedicinesAgency, SvenOftedal s

vei 6,N-0950 Oslo, Norway

E-mail: randi.winsnes@legemiddelverket.no; arnt.wisnes@sensewave.com;

winsnes@sensewave.com

PREFACE

Since itsﬁrst editionin 1989*the science ofvirology hasmoved forwardsat an

impressive pace.Modern technology has unravelledmany complex aspects of

the genetics,structure and immunology ofviruses, whereas the diagnosisand

treatment of our most common viral diseases have not enjoyed a similar

impressive development. However, recent years have given us several new

antivirals, and it is hopedthat we will also see new and better vaccines for

general use,as well as betterdiagnostic tools.

In this pocket-sized handbook we have attempted to meet the need for

condensed andreadily accessibleinformation aboutviruses asagents ofhuman

disease. Wehope that thisbook will provideuseful informationfor all health-

care professionals, in particular practising physicians, medical and nursing

students, interns and residents. We have included some new chapters on

hepatitis and herpes viruses to this new edition, whereas the arboviruses

chapter hasbeen taken out.

The cartoons will hopefully entertain as well as provide a helpful visual

image ofsome salient points.

The gestation period for this new edition was very long. Hopefully the

offspring willplease.

Bergen, London,Birmingham AL

March 2002

LARS R.HAAHEIM

Department ofMicrobiology and Immunology

University ofBergen

Bergen

JOHN R.PATTISON

Department ofHealth

Whitehall

London

RICHARD J.WHITLEY

Department ofPediatrics

The Universityof Alabama at Birmingham

Birmingham AL

*Edited by Haukenes G, Haaheim LRH, Pattison JR as a follow-upand extension of the

Norwegian bookHa

ndbok iklinisk virologi,Universitetsforlaget, Bergen,1983.

HELLO FOLKS!

PREFACE TO 1ST EDITION

In this pocket-sized handbook we have attempted to meet the need for

condensed andreadily accessibleinformation aboutviruses asagents ofhuman

disease. We have endeavoured to combine convenience with a concise but

comprehensive account ofmedical virology. In order to achieve our aims we

have broken withthe traditional designs oftextbooks and manuals. Thus all

mainchapter sare constructedin thesame waywith respectto headingsand the

location ofeach subjectwithin the chapter.The readerwill for instancealways

ﬁnd ‘Epidemiology’at thebottom of theﬁfth pageof a mainchapter. Inorder

to providea briefoverview asummary pagecontaining an abbreviatedform of

the subsequent information islocated at the beginning of each chapter.The

cartoon drawings also break with convention. Perhaps they will not only

amuse youbut proveto be instructiveand leavea visual imageof some salient

points.

The presentbook representsa developmentof a Norwegianbook (Ha

ndbok

i kliniskvirologi, Universitetsforlaget, Bergen, 1983)edited by twoof us (GH

and LRH). It is not a textbook but a guidebook, and we have therefore

included fourcomprehensive textbooks for furtherreading as references.

We hope this book will provide useful information for all health-care

professionals, inparticular practisingphysicians, medical students,interns and

residents.If the bookconvinces readersthat clinicalvirology ispart ofpractical

everyday medicine,we will have succeededin our aims.

Bergen andLondon

May 1989

GUNNAR HAUKENES

LARS R.HAAHEIM

Department ofMicrobiology and Immunology

University ofBergen

Bergen

JOHN R.PATTISON

Department ofMedical Microbiology

University Collegeand Middlesex School ofMedicine

London

xiii

ABBREVIATIONS

AIDS Acquired immunodeﬁciencysyndrome

Anti-HBc

Anti-HBe

}

Antibody againstthe hepatitis B viruscore, e andsurfa ce

Anti-HBs

antigens

Arboviruses Arthropod-borne viruses

ARC AIDS-related complex

ATL Adult T-cell leukaemia/lymphoma

AZT Azidothymidine

BL Burkitt’s lymphoma(EBV)

BKV Strain of humanpolyoma virus

CE California encephalitis(virus)

CF(T) Complementﬁxation (test)

CJD Creutzfeldt–Jakob disease

CMV Cytomegalovirus

CSF Cerebrospinal ﬂuid

EBNA EBV nuclearantigen

EBV Epstein–Barr virus

ELISA Enzyme-linkedimmunosorb entassay

F protein Fusion protein

Fr. French

Ger. German

Gr. Greek

H Haemagglutinin

HAM HTLV-associated myelopathy

HAV Hepatitis A virus

HBcAG

HBeAG

}

Hepatitis Bvirus core, e andsurface antigens, respectively

HBsAG

HBIG Hepatitis B immunoglobulin

HBV Hepatitis B virus

HCV Hepatitis Cvirus

HDV Hepatitis D (delta) virus

HEV Hepatitis E virus

HFRS Haemorrhagic fever withrenal syndrome

HI(T) Haemagglutination inhibition(test)

HIV Human immunodeﬁciency virus

HPS Hantavirus pulmonarysyndrome

HPV Human papilloma virus

HSV Herpes simplex virus

HTLV Human T-cell leukaemiavirus

IF(T) Immune ﬂuorescence (test)

IgA

IgG

}

Immunoglobulins ofthe classes A, Gand M, respectively

IgM

IL-2 Interleukin 2

JCV Strain of humanpolyoma virus

Lat. Latin

LCR Ligase chain reaction

N Neuraminidase

NANB Non-A,non-B (hepatitis)

NE Nephropathiaepidemica

NP Nucleoprotein

NPC Nasopharyngeal carcinoma (EBV)

NT Neutralizationtest

PCR Polymerase chain reaction

PGL Persistent generalized lymphadenopathy (HIVinfection)

PHA Passive (indirect) haemagglutination

PML Progressive multifocalleukoencephalopathy (polyoma virus)

RIA Radioimmunoassay

RIBA Radioimmunoblot assay

RSV Respiratory syncytial virus

RT-PCR Reverse transcriptasepolymerase chain reaction

SRH Single radial haemolysis

SSPE Subacute sclerosing panencephalitis (measlesvirus)

TBE Tick-borne encephalitis(virus)

TSP Tropical spastic paraparesis

URTI Upperrespiratory tract infection

VCA Viral capsid antigen(EBV)

VZIG Speciﬁc VZ-immunoglobulin

VZV Varicella–zoster virus

xvi

REFERENCES FOR

FURTHER READING

Collier L,Oxford J.Human Virology,2nd edn. OxfordUniversity Press,Oxford, 2000.

Knipe DM,Howley PM etal. (eds). Field’s Virology,4th edn. LippincottWilliams &

Wilkins, Philadelphia,2001.

Zuckerman AJ, Banatvala JE,Pattison JR (eds). Principles and Practice of Clinical

Virology, 4thedn. John Wiley& Sons,Chichester, 1999.

xvii

CLASSIFIED MATERIAL

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

1. CLASSIFICATION AND

NOMENCLATURE OF HUMAN AND

ANIMAL VIRUSES

Y. Ghendon

The present universal systemfor virus taxonomy includes family, genus and

species. Virus families and subfamilies are designated by terms end ing

in -viridae and -virinae,respectively. Families represent clusters of genera of

viruseswi thapparently commonevolutionary origin.Genera aredesignated by

terms ending in -virus. The criteria used for creating genera differ between

families.

Virus characteristics used for classiﬁcation vary from simple to complex

structure, includingnucleic acid andprotein composition, virionmorphology,

strategy ofreplication, physical and chemicalproperties, etc.

More than60 generaand about25 families ofhuman andanimal virusesare

recognized. Table 1.1 contains data on some familiesand genera of viruses

infecting man.

Table 1.1 CLASSIFICATION OFHUMAN VIRUSES

Family

Subfamily

Genus Examples

Double-stranded DNA,enveloped virions

Poxviridae

Chordopoxvirinae Orthopoxvirus Smallpox (variola),vaccinia

Parapoxviruses Orf

Molluscipoxvirus Molluscum contagiosumviruses

Yatapoxvirus Yabapox virus, Tanapoxvirus

Herpesviridae

Alphaherpesvirinae Simplex virus Herpes simplexvirus 1 and2

Varicellovirus Varicella-zoster virus

Betaherpesvirinae Cytomegalovirus Human cytomegalovirus

Roseolovirus Human herpesvirus 6

Gammaherpesvirinae Lymphocryptovirus Epstein–Barr virus

Double-stranded DNA,non-enveloped virions

Adenoviridae Mastadenovirus Human adenoviruses

Papovaviridae Papillomavirus Human papillomavirus

Polyomavirus Human BKand JC virus

continued

Table 1.1 continued

Family

Subfamily

Genus Examples

Partial double-strandedpartial single-stranded DNA,non-enveloped virions

Hepadnaviridae Orthohepadnavirus Human hepatitis Bvirus

Single-stranded DNA,non-enveloped virions

Parvoviridae

Chordoparvovirinae Erythrovirus Parvovirus B19

Double-stranded RNA,non-enveloped virions

Reoviridae Reovirus Reovirus types1, 2, 3

Rotavirus Human rotaviruses(A and B)

Orbivirus Orungovirus, Kemerovovirus

Coltivirus Colorado tickfever virus

Single-stranded RNA,enveloped virions withoutDNA stepin replication cycle

(a) Positive-sensegenome

Togaviridae Alphavirus Sindbisvirus (arbovirus groupA)

Rubivirus Rubellavirus

Flaviviridae Flavivirus Yellow fevervirus (arbovirus group

Unnamed Hepatitis C virus

Coronaviridae Coronavirus Human coronavirus

(b) Negative-sense,non-segmented genome

Paramyxoviridae

Paramyxovirinae Paramyxovirus Parainﬂuenzaviruses 1and 3

Morbillivirus Measles virus

Rubulavirus Mumps virus, parainﬂuenzaviruses2

and 4

Pneumovirinae Pneumovirus Respiratory syncytial virus

Rhabdoviridae Lyssavirus Rabies virus

Vesiculovirus Vesicular stomatitisvirus

Filoviridae Filovirus Marburg andEbola viruses

Orthomyxoviridae Inﬂuenzavirus A,B Inﬂuenza Aand Bviruses

Inﬂuenzavirus C Inﬂuenza C virus

Bunyaviridae Bunyavirus Bunyamweravirus, La Crossevirus,

California encephalitisvirus

Phlebovirus Sandﬂy fevervirus, Sicilian virus,

Rift Valleyfever virus,Uukuniemi

virus

Nairovirus Crimean–Congo haemorrhagicfever

virus

Hantavirus Hantaanvirus, Seoul virus,Sin

Nombre virus,Puumala virus

continued

Table 1.1 continued

Family

Subfamily

Genus Examples

Arenaviridae Arenavirus Lymphocytic choriomeningitisvirus,

Lassa virus,Venezuelan

haemorrhagic fevervirus

Single-stranded RNA,enveloped virions withDNA inthe replication cycle

Retroviridae HTLV–BLV group Human T-cell leukemia/

lymphotropic virus(HTLV-1 and

HTLV-2)

Spumavirus Human foamyvirus

Lentivirus Human immunodeﬁciency viruses

(HIV-1 andHIV-2)

Single-stranded RNA,positive-sense, non-enveloped virions

Picornaviridae Enterovirus Polioviruses 1–3, coxsackieviruses

A1–22, A24,B1–6, echoviruses 1–

7, 9,11–27, 29–33, enteroviruses

68–71

Hepatovirus Hepatitis A virus

Rhinovirus Rhinoviruses 1–100

Caliciviridae Calicivirus Norwalk agent, hepatitisE virus?

Figure1.1 MORPHOLOGICAL FORMSOF VIRUSES:1. poliovirus,naked RNA

virus with cubic symmetry; 2. herpesvirus, enveloped DNAvirus with cubic

symmetry; 3. inﬂuenzavirus, enveloped RNA virus with helicalsymmetry; 4.

mumps virus, enveloped RNA virus with helical symmetry—the helical

nucleocapsid is being released; 5. vesicular stomatitis virus, morphologically

similar torabies virus;6. orfvirus, alsowith acomplex symmetry.Bars represent

100nm (Electron micrographscourtesy ofE. Kjeldsberg)

A LOADOF TROUBLE

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

2. VIRUSES AND DISEASE

Virus¼ originally ‘poisonousmatter’.

G. Haukenesand J. R. Pattison

Viruses are the smallest known infectious agents. They are all built up of

nucleic acidand proteincoat(s) and mayin addition havean outerlipoprotein

envelope. Theyreplicate in cells andmay thereby leaddirectly to cell damage

and causedisease. Alternatively, thehost defences maylead to celldamage as

they attemptto clear virus-infected cells.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Virus infections are transmitted by inhalation, ingestion, inoculation,

sexual contactor transplacentally. Theincubation period differs greatly

and mayrange from afew days (e.g. thecommon cold) tomonths (e.g.

hepatitis B).

SYMPTOMS AND SIGNS

Systemic: Malaise, Fatigue,Fever, Myalgia, Asthenia

Local: Rash,Diarrhoea, Coryza, Cough,

Lymphadenopathy, NeckStiffness, Local Pain,

Pareses, Conjunctivitis

Most infections areacute and of short duration. Someviruses become

latent and may be reactivated, others are associated with persistent

replication andchronic disease.

COMPLICATIONS

The infection may involve organs other thanthe one most frequently

involved (e.g. orchitis inmumps). Complications may also result from

immunopathological reactions (e.g. postinfectious encephalitis in

measles) or from secondary bacterial infections (e.g. bacterial

pneumonia ininﬂuenza).

THERAPY AND PROPHYLAXIS

A fewantiviral drugs areavailable for clinicaluse in special therapeutic

and prophylactic situations. Immunoglobulins and vaccineshave been

prepared for prophylaxis against a considerable number of virus

infections.

LABORATORY DIAGNOSIS

Virus, viralantigen orviral genomemay bedetected inthe earlyphase of

acute disease by electron microscopy, immunological or molecular

biological methodsor virus isolation.Serologically the diagnosis canbe

made bydemonstration of seroconversion,antibody titre riseor speciﬁc

IgM.

Figure 2.1 VIRUSES AND DISEASE.(a) Measles. The virus canbe isolated just before andat the time of therash, followed by

appearance ofantibodies, clearanceof virusand lastingimmunity. (b) Inﬂuenza.The virushas ashort incubation period.Because of

theantigenic variationof inﬂuenzavirusthe immunityis soonoutdated. (c)Tick-borne encephalitis.The clinicalcourse isbiphasic. (d)

HIV infection.Infection has aprolonged coursewith persistence ofthe virus andantibody

CLINICAL FEATURES

SYMPTOMS AND SIGNS

Virus infections are mostly transmitted from acutely infected to susceptible

individuals through the common routes:airborne, food, blood (inoculation)

and directcontact. Some viruses infectthe fetus (e.g.CMV, rubellavirus) and

cause serious disease. Chronic and infectious carriers of virus are seen in

hepatitis B, hepatitis C, hepatitis D and in AIDS virus infections. The

incubation period may be a few days (upper respiratory infection, gastro-

enteritis), a few weeks (measles, rubella, mumps, varicella) or months

(hepatitis, rabies, AIDS). Prodromes are commonly seen at the time when

the virus spreads tothe target organ (e.g. in measles, rubella andvaricella).

Local symptomsare due to thecell damage causedby virus replicationin the

target organ leadi ng to inﬂammatory reactions (coryza, croup) or organ

failure/dysfunction (icterus). Systemicsymptoms (fever, malaise, myalgia)are

secondary torelease intothe circulationof denatured andforeign proteinfrom

infected and degenerating cells.Some systemic symptoms (e.g. erythematous

rashes) are immune mediated. Liberation of lymphokines from antigen-

stimulated T-lymphocytes also contributes to the inﬂammatory response.

Clinical signs are local inﬂammatory reactions such asoedema, hyperaemia

and seromucous secretions, and general reactions such as leukocytosis or

leukopenia with absolute or relative lymphocytosis. A polymorphonuclear

leukocytosis is occasionally observed (e.g. in tick-borne encephalitis).

Predominance of mononuclear cells is also found in the cerebrospinal ﬂuid

in meningitis.In acuteuncomp licatedcases theerythrocyte sedimentation rate

and C-reactive protein values are within normal ranges, and the nitroblue

tetrazolium testis usually negative unlessthere is extensive celldamage.

Differential diagnosis. It is of particular importance to exclude bacterial

infections requiring antibacterialtherapy, for example a purulent meningitis.

Microbiological examinations may be required to establish the aetiological

diagnosis.

CLINICAL COURSE

Most virusinfections are acuteand self-limiting, leadingto lifelong immunity.

Fulminant and lethal cases are usually the result of organ damage

(poliomyelitis, hepatitis,encephalitis). Some infectionshave a biphasicclinical

course (westerntick-borne encephalitis,epidemic myalgia). Someviruses cause

long-term infections. The pattern may be one of latency followed by

reactivation and clinical recurrence (e.g. herpesviruses). Alternatively, there

may be apersistent replication of virus but itmay take years before clinical

disease manifests itself (e.g. retroviruses and AIDS, hepati tis viruses and

cirrhosis).

COMPLICATIONS

There isno clear distinctionbetween that whichis considered tobe part ofan

unusually serious course and a complication. As a rule acomplication is a

manifestation of the spread of the infection to organs other than the most

frequent targets (e.g. orchitis and meningoencephalitis in mumps) or a

secondary bacterial infection (e.g. pneumococcal pneumonia following

inﬂuenza). In some infections immunopathological reactions may lead to

complications (e.g.postinfectious encephalitis in measles,polyarteritis nodosa

in hepatitisB).

THE VIRUS ANDTHE HOST

The virionhas acentrally locatednucleic acid enclosedwithin aprotein coreor

capsid. ‘Naked’ virusesare composed of this nucleocapsid only,while larger

viruses havean envelopein addition. Thenucleic acidis RNA orDNA, which

is single- or double-stranded. If the RNA is infectious and functions as

messenger RNA it is termed positive-stra nded, otherwise minus-stranded

(synonyms arepositive- ornegative-sense polarity). Onthe basis ofthe typeof

nucleic acid,the morphologyof thecapsid (cubical orhelical) andthe presence

or absence of an envelope, a simpliﬁed scheme for classiﬁcation can be

constructed (seeChapter 1).

Since thecell cannot replicate RNA, viruseswith an RNA genomefurnish

the cellwith an RNApolymerase. Thepolymerase constitutes partof the core

proteins ofnegative-stranded RNAviruses (e.g.inﬂuenzavirus), while positive-

stranded RNA viruses(e.g. poliovirus) encode the productionof the enzyme

without incorporating it. Retroviruseshave the enzyme reverse transcriptase

which catalyses the formation of DNA from viral RNA; RNA is then

synthesized from double-stranded DNA (provirus) by means of cellular

enzymes. The viral envelopeis a cell-derived lipid bilayer with insertedviral

glycoproteins. Theviral glycoproteins project fromthe surface of virusesand

infected cellsas spikes or peplomersand render the cellantigenically foreign,

and assuch a target forimmune reactions.

The pathogenesiscan inmost cases beascribed todegeneration and deathof

the infectedcells. Thismay bemedia teddirectly bythe virusor by theimmune

clearance mechanisms. Denatured proteins elicit local inﬂammatory and

systemic reactions. The local inﬂammatory response dominates the clinical

picture in some infections, such as common colds, croup and bronchiolitis,

while cell and organ failure or dysfunction is typical in poliomyelitis and

hepatitis. Some infections are particularly dangerous to the fetus (CMV

infection, rubella) or to the child in the perinatal period (herpes simplex,

coxsackie B,varicella-zost er,hepatitis B andHIV infections). Bronchiolitis is

seen onlyin theﬁrst 2 yearsof life, andcroup mostly inchildren belowschool

age. Otherwise the clinical course is not markedly different in children

compared withadults.

The defencemechanisms involvephagocytosis, humoral andcellular immune

responses and interferon production.In brief, interferon can arrest the local

spread ofthe infection in the earlyphase; antibodies restrict furtherviraemic

spread of the infection,mediate long-lasting immunity and sensitize infected

cells for killing by macrophages and T-cells; while the cellular immune

reactions includea seriesof eventsleading tothe developmentof cytotoxiccells

and release of lymphokines, including interfer on. In the recovery from

infection and protection against reinfection the various activities of the

defence mechanismsare very interdependent.

EPIDEMIOLOGY

Human pathogenic viruses are maintained in nature mostly by continuous

transmissions from infected humansor animals to susceptible ones. Chronic

carriers ofvirus are important humanreservoirs for hepatitisB and HIV and

forsome herpesviruses. Animalreservoirs playa rolein rabies,in ﬂavivirusand

other ‘arbovirus’infections, and inhaemorrhagic fevers.Some virus infections

lead toovert diseasein mostcases (measles, mumps,varicella, inﬂuenza)so the

spread ofthe epidemiccan easily befollowed. In othersclinical manifestations

are exceptional (hepatitis B, enterovirus andCMV infections) and epidemic

surveys mayrequ irelaboratory tests. A balanceis usually established forthe

maintenance ofa virus in humanpopulations. Antigenic changes (drift,shift)

provide the underlying reason for epidemic spread of virus variants and

subtypes (inﬂuenzavirus).A virusinfection maybe eradicatedas with smallpox

and,in thecase of encephalitislethargica (vonEconomo’s disease),an infection

appeared, existedfor 10 years andthen vanished.

THERAPY AND PROPHYLAXIS

Some progress hasbeen made in thedevelopment of antiviral drugsin recent

years. Main obstacles to a rapid breakthrough seem to be the rather late

appearance of symptoms in relation to tissue damage and the potential

cytotoxic effectof inhibitors of virus replication.Examples of antiviral drugs

which areused clinicallyare aciclovir andtriﬂuorothymidine inherpes simplex

and varicella-zoster virus infections , azidothymidine in HIV infection and

interferon inchronic activehepatitis Band C.Amantadine hasproved effective

in theprophylaxis of inﬂuenza A.Antivirals are dealt with in Chapter 4.

Immunoglobulins may provide short-term protection against certain virus

infections. Normal human immunoglobulin is used in the prophylaxis of

measles andhepatitis A,while speciﬁc immunoglobulins(produced from high-

titred plasma) are needed for other infections (rabies,hepatitis B, varicella-

zoster). A requirement for being effective is that the immunoglobulins are

administered asearly aspossible after exposure,i.e. beforethe viraemic spread

to thetarget organ.

Vaccines are now available against a number of virus infections. The

vaccines are composed of either live attenuated virus (e.g. rubella, mumps,

measles), inactivated whole virus(e.g. rabies, inﬂuenza) or viral components

(e.g. inﬂuenza, hepatitis B). Second- and third-generation vaccines are

recombinant DNA vaccines (hepatitis B) and synthetic peptide vaccines,

respectively.

LABORATORY DIAGNOSIS

The aetiologicaldiagnosis can be establishedby demonstration of virus,viral

antigen orspeciﬁc antibody. Asa rule, virus orits antigens orgenome can be

demonstrated inthe early acute phaseof the disease, whileantibodies appear

from 5to 20 days afterexposure. Demonstration of virusin specimens taken

from theaffected organis usuallyof diagnosticsigniﬁcance, althoughexcretion

of viruses(enterovirus, adenovirus) not associatedwith the disease concerned

has tobe considered.Demonstration of aconcomitant antibodytitre rise orof

speciﬁc IgM may be valuable additionalevidence. As many virus infections

have anasymptomatic course, the meredemonstration of speciﬁc antibodyis

of limitedvalue unless there isa titre rise orspeciﬁc IgM is found.It may be

difﬁcult to distinguish reinfection or reactivation from a primary infection.

Usually theIgM responseis moremarked inprimary infections.All laboratory

ﬁndings have tobe evaluated in relationto the recorded time ofexposure or

onset of symptoms. It is important that the clinician gives adequ ate and

relevant informationto the laboratory.In return thelaboratory will comment

on theﬁndings and advise regardingadditional samples.

Laboratory testing is also performed in order to establish the immunity

status of an individual. The methodsused for screening (IgG tests) may be

different fromthose usedfor establishing thediagnosis inacute infection (IgM

testor paired seraexamination). Theclinician shouldtherefore alwaysstate the

clinical problem.Laboratory diagnosisis discussedin moredetail inChapter 3.

JUST TAKEA SAMPLE FORVIRUS STUDIES

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

3. LABORATORY DIAGNOSIS OF

VIRUS INFECTIONS

G. Haukenesand R. J. Whitley

Most virus infections runan asymptomatic course, or they are so mildthat

medical attention is not required. In many clinical cases an accurate

aetiological diagnosis can be made solely on the basis of the clini cal

manifestations of the disease. Thus most cases of measles, varicella, zoster

and mumpsare diagnosed bythe patient, hisor her relatives,or by thefamily

doctor. By contrast in other clinical situations, the resourc es required to

establish an aetiological diagnosis are too great to justify virological

examinations, forexample in rhinovirus infections.

WHEN SHOULD VIROLOGICALTESTING BE ORDERED?

In all clinical work the beneﬁt of a precise diagnosis is indisputable. The

consequences for the treatment of individual patients are obvious, and

preventive measures can be taken to reduce the risk of transmitting the

infection toothers. In epidemics thelaboratory diagnosis ofa few early cases

also beneﬁtsthe doctor inthat it allows conﬁdentaetiological diagnosis tobe

madefor subsequent similarclinical cases.National andglobal epidemiological

surveillance and control programmes will also require data fromdiagnost ic

laboratories. Decisionas to thecurrent composition ofan inﬂuenza vaccineis

one such example.The most common clinicalsituations requiring virological

laboratory examinationsare:

. Respiratory infections. Small children with severe respiratoryillnesses and

all agegroups when inﬂuenza issuspected.

. Gastroenteritis. In general allcases which are severe and when thereis an

epidemic inprogress.

. Mumps. In sporadic or doubtful cases, and in cases of orchitis,

meningoencephalitis or pancreatitis when the clinical diagnosisof mumps

is not certain. Immunity status screening for vaccination of adult or

prepubertal males.

. Rubella. When rubella issuspected in a pregnant woman or inher family

contacts. Theimmunity status of awoman should always beestablished in

connection withpremarital orfamily planning consultationsand onthe ﬁrst

consultation in her pregnancy. All cases of suspected congenital rubella

require laboratoryconﬁrmation.

. Measles. In clinicallydoubtful cases, when SSPE is suspectedand in cases

of postinfectiousencephalitis of unknown cause.

. Varicella. When the rash is not typical. Immunity status should be

established in children before treatment with cytotoxic drugs and in

women exposedto varicella in thelast trimester ofpregna ncy.

. Zoster. Veriﬁcation of the clinical diagnosis may be desirable, also for

selection ofdonors of blood forpreparation of hyperimmunoglobulin.

. Herpes simplex. In pregnancy, especially when genital herpesis suspected

before delivery.In severeherpes simplex,generalized herpesvirusinfection in

newborn infantsand cases of encephalitis.

. Cytomegalovirus infections. Screening of blood donors an dof donors and

recipients oftissues andorgans. Cases ofprolonged feveror mononucleosis-

like disorders when heterophileantibody and anti-EBV tests are negative,

especially if occurring during pregnancy or as part of a post-transfusion

syndrome. Prolonged fever of unknown cause. Fever and pneumonia in

immunocompromised individuals.

. Epstein–Barr virus (EBV)infections. When infectious mononucleosisis sus-

pectedand thediagnosishas notbeen madebytests forheterophile antibodies.

. Hepatitis. Allcases of hepatitisshould be examinedfor viral antigenand/or

antibody. High-risk groups are screened for the chronic carrier state of

hepatitis B and C viruses. Blood and tissuedonors must be screened for

HBsAg andanti-HB cand for anti-HCV. Immunitystatus is determined in

high-prevalence or high-riskgroups before vaccination against hepatitisB,

or before vaccination or the repeated use of normal immunoglobulin to

prevent hepatitisA.

. Erythema infectiosum.The clinical diagnosismay be uncertain, especiallyin

non-epidemic periods. When parvovirus B19 infection is suspected in

pregnancy. Casesof arthralgia.

. Meningitis, encephalitis and other severe disorders of the nervous system

require microbiological and serological examinations to establish the

aetiology.

. HIV infection.The clinical manifestations inany phase ofan HIV infection

comprise awide rangeof syndromes,which willrequire testingfor anti-HIV.

Subjects at risk of contracting HIV infection have to be examined in

accordance with national control programmes. All donors of blood and

tissue (includingbreast milk) should betested for anti-HIV.

. HTLV infection. Cases of T-cell leukaemia and progressive spastic

paraparesis of unknown cause in individuals who may be at risk of

exposure toHTLV-1. Screening of bloodand tissue/organ donors foranti-

HTLV-1/2 inaccordance with national controlprogrammes.

LABORATORY DIAGNOSIS

Virological diagnosis is based either on demonstration of the virus or its

components (antigensor genome) or ondemonstration of a speciﬁcantibody

response. In someinfections antibodies are detectable atthe onset of clinical

disease (e.g.poliomyelitis, hepatitis B(anti-HBc)), orthe antibody appearance

may be delayed by days (rubella), weeks or months (hepatitis C, HIV

infection). Whenever an early diagnosis is important for the institution of

antiviral therapy or some other interference measures, the possible use of

methods thatdemonstrate the virus shouldbe considered.

The virus can be demonst rated directly by electron microscopy (gastro-

enteritis viruses,orfvirus). Alternatively,infec tiousvirus maybe demonstrated

after inoculation ofcell cultures (enteroviruses, adenoviruses, herpes simplex

virus, cytomegalovirus), embryonated eg gs (inﬂuenzaviruses) or laboratory

animals (coxsackievirus). Clinicians should carefully follow the instructions

issued bytheir local laboratories withregard to sampling andtransportation,

especially ifinfectivity has to bemaintained.

Viral genomes can be demonstrated by various nucleicacid hybridization

techniques, either insitu or in tissueextracts (slot blot, Southern blot,in situ

hybridization) usinglabelled DNAor RNAprobes, orby methodsthat include

ampliﬁcation ofthe viralnucleic acidsuch as polymerasechain reaction(PCR)

and ligasechain reaction (LCR).Both PCR andLCR are extremelysensi tive,

requiring strictprecautions inthe laboratoryto avoidcontamination. Thegen e

technology methods are of particular importance for rapid diagnosis of

infections that are accessibleto antiviral treatment (herpes simplex encepha-

litis, CMV infection), for diagnosis of infectionwith viruses that cannot be

cultivated (human papillomaviruses) or viruses that grow slowly in culture

(enteroviruses), as well as in clinical situations where a deﬁnite diagnosis

cannot bemade byother means(possible HIVinfection andhepatitis B orC in

newborns andinfants).

Several virus antigen tests are available for rapid diagnosis of virus

infections. Methods most commonly used are immunoﬂuorescence or

immunoperoxidase for respiratory viruses, ELISA for HBsAg, HIV and

rotavirus, latexagglutination forrotavirus, andreverse passivehaemagglutina-

tion for HBsAg. Immunoﬂuorescence and immunoperoxidase procedures

depend on the sampling and preservation of infected cells, requiring rapid

transport ofcooled material. Alternatively, preparation ofthe slide has tobe

made locally.Blood (serum) and faecescan be sentin the usual way.

Antibody examinations are mostly performed with serum. Anticoagulants

added to whole blood may interfere with complement activity and enzyme

functions, andshould be avoided. Incertain situations (SSPE,herpes simplex

encephalitis) antibody titration is performed on cerebrospinal ﬂuid. Acute

infection is diagnosed by demonstrating a rise in titre, seroconversion or

speciﬁc IgM(or IgA).A risein titremay beseen bothin primaryinfections and

in reinfection or after reactivation. A positive IgM test usually indicates a

primary infection, but lower concentrations of speciﬁc IgM are found in

reactivations (CMVinfections andzoster) and reinfections(rubella). A variety

of methods (complement ﬁxation (CF), haemagg lutination inhibition (HI),

enzyme-linked immunosorbent assay(ELISA), immunoﬂuorescence (IF)) are

available fordemonstration ofantibodies, andthe choiceof testwill dependon

the virusand whether theclinical problem isthe immune statusor diagnosing

an acuteinfection. Bloodsamples for demonstrationof seroconversion ortitre

rise (pairedsera) aretaken 1–3weeks apart,depending on thetime ofexposure

or onsetof symptoms.

INTERPRETATION OF RESULTS

To achievethe full beneﬁt ofvirological tests, appropriatespecimens must be

taken at the optimum time and must be transported to the laboratory as

recommended. Inthe laboratory,the virologistwill decide onappropriate tests

on the basisof the information given by the clinician.This information will

also be important for the interpretation of thelaboratory ﬁndings. Thus, a

meaningful laboratoryservice depends on collaborationbetween the clinician

and thevirologist.

Isolation ofa virus doesnot prove that thevirus is thecause of theclinical

conditionconcerned. Enteroviruses, forexample, maybe shedinto thepharynx

and the intestines for long periods after an acute episode. A concomitant

antibody titre risesupports the evidence ofa causal connection. By contrast,

isolation ofa virus fromthe blood orfrom the cerebros pinalﬂuid willusually

be diagnosticwhatever the antibody ﬁndings.

The mere demonstration of a high antibody titre is of limited diagnostic

value and will have tobe evaluated in relation to the clinical problem. The

virologist will know the time after exposure or onset of symptoms that

antibodies aredetectable, when anantibody titre riseis expected,and for how

long itmay be possible todemonstrate speciﬁc IgM. Itis therefore of crucial

importance thatthe clinician providesthe relevantdata about timeof possible

exposure andonset of symptoms,and, insome clinical situations,information

about pregnancy and vaccinations.The virologist can then comment on the

ﬁndings andadvise further tests ifindicated.

THE CONSTRUCTIONCOMPANY

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

4. ANTIVIRAL DRUGS

J. S.Oxford and R. J.Whitley

The historyof antiviralchemotherapy as ascience isshort, commencing inthe

1950s with the discovery ofmethisazone which is a thiosemicarbazone drug

inhibiting thereplication of poxviruses. Theexperience of clinical application

of antiviralsis even shorter and mostcomprehensively involves 24 important

licensed drugs: amantadine and the related molecule rimantadine, primary

amines which inhibitinﬂuenza A viruses; the newerantineuraminidase drugs

which inhibit both inﬂuenza A and B viruses; aciclovir and related acyclic

nucleoside analoguesinhibiting herpes type Iand type II; zidovudineand the

group of dideoxynucleoside analogues , non-nucleoside inhibitors of HIV

reverse transcriptase and also inhibitors of the viral protease enzyme. Very

extensive usehas beenmade of aciclovirand the anti-HIVmolecules, bringing

wide recognitionto the scienceof antivirals. Infact the moststriking example

of the potential of antivirals was the discovery and clinical application of

zidovudine, within2–3 years of theﬁrst isolation of theHIV-1 itself, and the

more recentdiscovery and use inthe clinic of additionalantir etroviraldrugs.

As acomparison, and aftera further 15years of hardwork, effective vaccines

against HIVhave yet to bedeveloped.

But, ofequal importanceto the searchfor new inhibitors ,is theattention to

strategies to useexisting compounds sensibly and tomaximum clinical effect

without squandering the discoveries. Viruses, particularly RNAviruses, can

mutate rapidly andthus drug resistance to virusescou ldquickly become the

major problem it already is with antibiotics and bacteria. Antivir al

chemotherapists have already beneﬁted from the clinical experience of

preventing drug resistance against mycob acteria by using three drugs

concurrently andcombinat ionsof two or threeantivirals are now beingused

successfully toprolong the life ofAIDS patients.

In the presentchapter we will outline someof the underlying principlesof

antiviralchemot herapy,place emphasison themost importantexisting licensed

drugs and attempta short stargaze into thefuture. Unfortunately the future

may look alittle bleak. History hascome full circle and chemotherapistsare

now activelysearching for new drugsagainst smallpox virus.

THE TARGET VIRUSES

HIV-1 is,and will probably remain,the prime focusof attention for antiviral

chemotherapists fortwo reasons,namely medicaland economic(Table 4.1).As

regards the latter, it should be appreciated that a minimal cost of a drug

development is$0.5 billion.A pharmaceutical companywill notdevelop drugs

againstrare viraldiseases. Front-linetarget virusesare thereforeHIV-1, herpes,

inﬂuenza andcommon coldviruses, with morerecent attention onhepatitis B,

hepatitis Cand papilloma viruses.There isa further importantfact which will

encourage chemists to produce even more antivirals. A quasi-species RNA

virus suchas HIVexisting asa ‘swarm’of countless geneticvariants willeasily,

Table 4.1 FEATURES OFTHE TARGET VIRUSESFOR CHEMOTHERAPY

Virus Why are furtherantivirals required? Potential problems

HIV No vaccine exists.Retrovir and the

other dideoxynucleosideanalogues,

non-nucleoside inhibitorsand also

protease inhibitorshave only limited

efﬁcacy. Thevirus is worldwideand

spreading rapidlyin Asia anddrug-

resistant virusesare emerging

Drug resistance

Inﬂuenza Epidemics occuryearly resulting in

serious morbidityand death in

‘at risk’groups. The vaccineis not

100% effective.Periodically worldwide

pandemics sweepthe world. Twonew anti-

NAdrugs have beenlicensed recentlyto join

the M2blocker amantadine (Lysovir)

Drug resistance

Human herpes

viruses

(HHV1–8)

No vaccinesexist. The diseaseis lifelongand

recurrent infectionsare common. Prodrugs

are nowutilized but successful

chemotherapyis restricted toone memberof

this largefamily, HSV-1

None

Respiratory

viruses

A myriadof 150 commoncold viruses,six

adenoviruses, fourparainﬂuenzaviruses and

coronaviruses inhabitthe upper respiratory

tract. Theymay trigger seriousbacterial

infections orattacks of bronchitis

Impossible to

differentiate

clinically and

hence abroad

spectrum

antiviral willbe

required

Hepatitis B

and Cviruses

Very commoninfections in manyareas of

the world.Interferon a isused inthe

clinic, asis lamivudine (3TC)and

famciclovir againsthepatitis B

Persistent chronic

infection

Human

papilloma

(wart) viruses

Common viruswhich can bespread

sexually

None envisaged

Smallpox The threatof reemergence ofmonkey pox

and camelpox or theuse ofbioterrorism

by mutation and selection, evade the blocking effects of a single inhibitor.

Therefore, as withtuberculosis, the practical answeris to ﬁnd inhibitorsof a

wide rangeof virus-speciﬁc enzymes or proteinsand to use themin a patient

simultaneously. Thissearch fornew drugswill bea continuingneed asit iswith

antibacterials. Similarly, inhibitors of pandemic and epidemic inﬂuenza A

viruses will need the continuing attention of antiviral chemotherapists. The

human herpes viruses (HHV1–8) cause a remarkably diverse range of

important diseases and will continueto remain important targets, especially

VZV (varicella-zostervirus or shingles),which will reachnew importance ina

world population withincreasing longevity. Common cold viruses andother

virusesof the respiratorytract causepathogenesis inthe upperrespiratory tract

during all months of the year inall countries of the world and hence have

economic importance.The eightor sohepatitis viruses, andespecially hepatitis

B and C, are increasingly recognized as virus diseases where chronic or

prolonged infection gives extensive opportunity to the application of

therapeutic drugs. Papilloma viruses are extremely common, are considered

to be oncogenic and can be spread sexually. Sadly we have now to add

smallpox toour list asa possiblebioterrorist virus. Butthere is anotherlesson

to belearnt here: thereare other poxviruses from monkeysand camels which

cause disease inhumans and they could emerge naturally,and in fact, are a

bigger threatto our safety thana deliberate release.

There is therefore no shortage of viral targets for new drugs. The main

problem, as ever, isthe actual discovery of a novel drug. Itmust be clearly

recognized that all the antivirals yet discovered have an extraordinarily

restricted antiviral spectrum. For example, amantadineinhibits inﬂuenza A,

but not inﬂuenza B virus, whilst aciclovir is highly effective against herpes

simplex type Ibut has little or no effectagainst the herpes cytomegalovirus.

Similarly the neuraminidase inhibitorsonly target inﬂuenza A and Bviruses

and haveno effect against virusesof other familiessuch as paramyxoviruses.

HOW ARE NEWANTIVIRALS DISCOVERED?

To thepresent day ourantivirals have beenfound by truePasteurian logic, to

be paraphrased as ‘discovery favours with prepared mind’. In practical

laboratory terms‘off-the-shelf’ chemicals are subjectedto a biological screen.

A virus-susceptible cell line is incubated with a non-toxic concentration of

novel drug and the ‘target’ or ‘challenge’ virus is then added. If the cellis

rendered uninfectableor if there isa 10–100-fold reductionin the quantity of

virions producedby the drug-treatedcell, the drugis further investigated.The

many stagesof thelifecycle of avirus give chemotherapeutiststhe opportunity

to design or ﬁnd compoundswhich interrupt virion binding, penetration or

more usually somevital step dependent upon a uniqueviral enzyme such as

RNA polymerase,protease or integrase(Table 4.2). Virologists havescreened

through libraries of millionsof already synthesized compounds, either using

biological or, increasingly,automated ELISA screens against particular viral

proteins. Oncea molecule binding toa viral proteinhas been located,a more

efﬁcient molecule can be ‘designed’ by the chemists. Excellent examples of

semi-designed antivirals areinhibitors of the commoncold virus, which bind

tightly to the viral capsid protein and which can be visualized by X-ray

crystallography inthe bindingpocket on the virion surface,and alsoinhibitors

of the inﬂuenzavirus neuraminidase enzyme. In the latter case the enzyme-

active sitehad beenidentiﬁed asa saucer-like depressionon thetop ofthe viral

Table 4.2 STEPS IN VIRUSREPLICATION THATARE SUSCEPTIBLETO INHIBITORS

Target Antiviral Virus/infection

(1) Virusadsorption Dextran sulphate

CD4 (receptor)

HIV-1

(2) Viralpenetration and

uncoating

Amantadine (Symmetrel

or Lysovir)*

Rimantadine*

gp41 peptides(fusion)

Inﬂuenza A

HIV-1

(3) Virus-inducedenzymes Zidovudine(AZT) HIV-1

Reverse transcriptase

DNA polymerase

Zalcitabine (ddC)

Didanosine (ddI)

Stavudine (D4T)

Lamivudine (3TC)

Delavirdine

Nevirapine

Efavirenz

Aciclovir (ACV)*

Penciclovir*

Generalized herpes

and shingles

infections andgenital

HSV infections

Ganciclovir* Cytomegalovirus

infections (e.g.

pneumonia)

Triﬂuorothymidine* (TFT) Eye infectionswith

HSV

Foscarnet CMV infections

Cidofovir Pox viruses

Protease Saquinavir*

Indinavir*

Neﬁnavir*

Ritonavir*

HIV

Neuraminidase Zanamivir*

Oseltamivir*

Inﬂuenza Aand B

Viral proteinsynthesis Interferon* Many viruses

Free virusparticle Pleconaril Rhinoviruses

*Alicensed antiviral.

neuraminidase protein an d X-ray crystallography identiﬁed exactly which

amino acids ofthe viral protein were interactingwith an inhibitor. Chemists

have modiﬁedan already discovereddrug byaddition of asingle side chainto

enable it to bind more strongly tothe inﬂuenza neuraminidase protein and

hence causestronger inhibition ofviral replication. The effectsoccur at alate

stage of viral growth where the function of the neuraminidase is to cause

release ofnewly synthesized virus fromthe infected cell.

But, do not forget that the members of the plant kingdom are excellent

chemists aswell and laboratories areintensifying the searchto discover novel

molecules inplant extracts which,by chance, inhibitviruses. There isa strong

history here to remember, with A. Fleming’s discovery of the penicillin

antibiotic, synthesizedby a penicillium mouldon an orange.

Chemists also belie vethat thousands of nucleosideanalogues remain to be

synthesized and tested as antivirals. Alternatively, these compounds may

already be in existence and on the shelf as part of a completely unrelated

biological screening programme. The now classic anti-herpes nucleoside

analogue aciclovir was initiallysynthesized as an anti-cancer drug. Aciclovir

is structurally related tothe natural nucleoside 2’ deoxyguanosine but hasa

disrupted sugar ring (acyclic). Nucleoside analogues are some of our most

powerful antiviralsand even more surprisinglysome, like aciclovir, appearto

Table 4.3 RELATIVELY FEWPOINT MUTATIONS INVIRAL GENES CANLEAD TO

DRUG RESISTANCE

Virus Drug Specific mutations

responsible forresistance

Inﬂuenza A Amantadine, zanamivir

and oseltamivir

Mutations inM2 gene

(amantadine) and

possibly inHA gene and

NA genes(oseltamivir

and zanamivir).

Fortunately NAmutants

are lessable to spread

Herpes simplex Aciclovir Mutations intheviral DNA

polymerase orTK

enzyme. Importantly,

some viruseswithout

thymidine kinaseor

possessing analtered TK

may beless virulent

in vivoand so willnot

spread

HIV-1 Zidovudine and other

dideoxynucleoside

analogues

Five mutationsin the

reverse transcriptasegene

Protease inhibitors Mutations in theHIV

protease

be extraordinarily safe in the clinic and, not surprisingly, have become the

virologists’ favouritemolecule.

HOW IMPORTANT APROBLEM IS DRUG RESISTANCE?

It must be acknowledged that the high mutation rates of the classic RNA

virusessu chas inﬂuenzaand HIVwill alwaysresult in‘resistance’ problemsfor

antiviral drugs.With inﬂuenzaA virus asingle mutationin the targetM2 gene

allows the mutatedvirus to escape fromthe inhibitory effects of amantadine

(Table4.3). Similarly withHIV-1, aminoacid changesin thetarget viralreverse

transcriptase enzymeallow the virusto replicate inthe presence ofzidovudine

and otherdideoxynucleoside analogues. Recentstudies have shownthat drug-

resistant HIV mutants emerge within days of initiation of treatment of an

infected patient with certain dideoxynucleoside analogues. This has led to

the use of combination chemotherapy (highly active antiretroviral therapy

(HAART)) usingthree inhibitors, two against theRT enzyme andone against

the protease enzyme. With aDNA virus such as herpes the drug resistance

problem is correspondingly less acute because of the lower virus mutation

rates. There areproofreading enzymes already in thecell to correct errorsin

DNA-to-DNA transcription, but not to correct RNA-to-DNA or RNA-to-

RNA molecularevents. Theﬁrst clinicaltrial inAIDS patients establishedthat

the mortalityfollowing administration ofzidovudine alone was17%, whereas

if a patient was also administered didanosine or zalcitabine the mortality

dropped to10 and12%, respectively.Addition of proteaseinhibitors andnon-

nucleoside inhibitors adds further beneﬁts. These extra clinical beneﬁts are

assumed to accrue partly because of avoidance of drug resistance.

Furthermore, DNA polymerase enzymes have a higher ﬁdelity of reading

and fewer transcription mistakes occur. However, although mutation rates

maybe 1000-foldless withherpesvi rusthan withan RNAvirus, drugresistance

does occurin immunosuppressed patients undergoingtransplantation surgery

or in AIDS patients where herpesviruses with mutations in the thymidine

kinase gene allow the mutant to escape from the effects ofaciclovir. So in

immunocompromised patients theexceedingly rare mutated viruscan emerge

and dominatethe virus population inthe patient.

The experience ofclinical bacteriologists treating infectionswith Mycobac-

teria tuberculosishas ledto the useof combinationsof two orthree drugs with

different pointsof action. Forexample, ifthe chance ofa zidovudine-resistant

mutant ofHIV occurring is10

, thenby treating apatient with threeantiviral

drugsat thesame timethe chanceof amutant arisingwith simultaneousgenetic

changesat allthreecritical viralsites wouldexceed10

(butwith adifferenttarge t

for each) and would therefore be vanishingly small. We have therefore

entered thetime ofcombination chemotherapyfor viruses, particularlyHIV.

HOW ARE ANTIVIRALSUSED IN CLINICAL PRACTICE?

Antivirals can be used prophylactically to prevent a virus infection in a

person who hasnot yet been infectedbut who will be incontact with others

who are infected, in much the same way as most vaccines are used.

Prophylactic protection witha chemical antiviral ismore rapid in onset than

that induced by vaccines, since some antiviral protection would be

anticipated within 30 minutes of drug administration. Most antivirals are

administered bymouth and rapidadsorption of drugand spread toall tissues

of the bodyis often achieved. Tomaintain active levels of drugin the target

organ redosingis required, perhaps twicedaily. Clinical useis less convenient

if oral absorption is poor, and if the drug has to be given by intravenous

infusion or, in the case ofrespi ratoryinfections, by aerosol or nasal spray.

However, itcould be argued thatwith respiratory infectiondirect application

of a drug tothe nose and airways could have medicaladvantage s.

Two anti-herpes prodrugs and morerecently an anti-inﬂuenza neuramini-

dase inhibitor have beenstudied and licensed, which are inactive themselves

but areconverted by enzymesin the patientto the activeantiviral (prodrugs).

It should be remembered that when drugprophylaxis is discontinued the

patient becomessusceptible tovirus infection unlessa subclinical infectionhas

occurred inthe ﬁrst instance, givingthe patient someimmunity to reinfection

with thesame virus.

An example ofprophylaxis is the use ofamantadine or the neuraminidase

inhibitors toprevent spreadof inﬂuenza Avirus withinfamilies. The drugsare

given tothe familymembers whoare stillwell, but incontact withan illperson

perhaps intheir ownfamily. Under thesecircumstances nearly90% protection

can beachieved.

Most often antivirals are used therapeutically, being administered either

after infectionor even after theﬁrst clinical signs ofthe disease are noted.In

this situation further progression of the disease may stop and/or the virus

infection mayresolve morerapidly. Therapyis thefavoured mode withHIV-1-

infected patients,although the drug may begiven before overtclinical signs of

disease bothto delay thetime before earlysymptoms occur andalso to lessen

the chanceof drugresistance occurring. Thereis stillactive debateabout when

to initiatechemotherapy, earlyin thediseas eor later.Aciclovir maybe used to

prevent recurrent herpes infections andthis is a therapeutic use because the

patient isalready infectedwith the virus.The threeanti-inﬂuenza drugs canall

be used to ameliorate clinical sympt oms and also to prevent secondary

complications ofinﬂuenza, buthave to begiven to thepatient within48 hours

of onsetof symptoms.It shouldbe appreciatedthat evenexperienced clinicians

are still ona learning curve with theprevention and treatment of most viral

infections usingantivirals.

WHICH ARE THECLINICALLY EFFECTIVE ANTIVIRALS?

A shortlis tof antivirals in orderof their clinical usefulnessand effectiveness

would be headed by aciclovir, followedby the dideoxynucleoside analogues

and the newneuraminidase inhibitors and, ﬁnally, amantadine (Figures4.1–

4.3). A rangeof retroviral agents arenow used against HIV-1and several of

Figure 4.1 CLINICALLY EFFECTIVEDRUGS AGAINST HERPESVIRUSES

Figure 4.2 CLINICALLY EFFECTIVEDRUGS AGAINST HIV

these drugs, including non-nucleoside inhibitorsof reverse transcriptase and

protease inhibitors,are listed inTable 4.2. Theinhibitors of HIVprotease are

used in combination with AZT and, perhaps, ddI or ddC as a drug

combination. Also a prodrug of aciclovir called valaciclovir has been

developed. Thisis the

L-valineester of aciclovirand afterabsorption undergoes

almost completehydrolysis to aciclovir andthe essential amino acid

L-valine.

Valaciclovir its elfhas negligiblepharmacological activityand allproducts ofits

metabolism except foraciclovir are inert orwell characterized. Of course the

most importantproduct ofits metabolismis acicloviritself. Thecrucial pointis

that theoral prodrug leadsto 3–5 timesenhanced bioavailability ofthe active

Figure 4.3 CLINICALLY EFFECTIVEDRUGS AGAINST INFLUENZA

aciclovir, enabling less frequent doses and higher plasma levels. Similar in

conceptis the clinicalapplication ofthe prodrugfamciclovir whichis converted

enzymatically inthe patientto the activeanti-herpes nucleoside analoguedrug

penciclovir (Figure4.4). Anexpanding focus iswith hepatitisB virus wherean

estimated 5% ofthe world are chroniccarriers of the virusand combination

chemotherapy with lamivudine, adefovir and famciclovir is being tested

experimentally.

ACICLOVIR AND OTHERANTI-HERPES DRUGS

Nucleoside analoguepred ecessor sof aciclovir suchas idoxuridine (IDU) and

triﬂuorothymidine (TFT)were useful for treatingsuperﬁcial herpes infections

(including those of the eye), whilst adenine arabinoside (ara A) had an

important and pioneering role in the treatment of herpes encephalitis and

serious paediatricinfections. However,the advent ofaciclovir transformed the

often difﬁcult clinical management of herpetic infections and these earlier

discovered drugs, with the possible exception of TFT, are no longer used.

Aciclovir is used as a prophylactic, before surgery for example, to prevent

recurrent herpes type I infections in bone marrow and heart transplant

patients, andtherapeutically toprevent spread ofmucocutaneous infections in

already infectedand immune compromisedpersons. Ithas also beenshown to

bevery effective insaving liveswhen usedto treatherpes encephalitis.Aciclovir

is alsoused against recurrentHSV infections, particularly thoseof the genital

tract, andto alesser extent invarious forms ofVZV infections. Actuallythere

is an urgentneed for highly active drugsagainst VZV and thisinfec tionwill

come evenmore to the public’s noticeas the population ages.More effective

against VZVis the prodrug ofaciclovir, valaciclovir which isbetter absorbed

orally andis rapidly converted toaciclovir in vivo.

A molecular relative ganciclovir, has antiviral activity against cyto-

megalovirus (CMV) and is used to treat life-th reatening CMV infections

after bone marrow transplants, or CMV pneumonia or retinitis in AIDS

patients. However,unlike aciclovir thedrug induces rathersevere neutropenia

and thrombocytopenia. Although CMV does not have a viral TK enzyme,

Figure 4.4 FAMCICLOVIR ASA PRODRUG OFPENCICLOVIR

another viral protein phosphorylates ganciclovir tothe monophosphate and

thereafter a cellular enzyme phosphorylates the molecule to ganciclovir

triphosphate, whichinhibits CMV DNA polymerase.

Foscarnet, which is not a nucleoside analogue, can be used to treat

intractable casesof CMVbut the drugis administered inhospitals underclose

clinical care.

Aciclovir possesses an excellent combination of pharmacological and

antiviral propertieswhich helps to explainits unique and highlyspeciﬁc anti-

herpesvirus speciﬁcity.Firstly, thecompound isonly phosphorylatedin herpes-

infected cells,since theherpes thymidinekinase enzymeis less‘precise’ thanthe

corresponding cellular enzyme andwill accept fraudulent substrates, such as

aciclovir. This meansthat any potential drug-inducedtoxic ityis immediately

avoided orat leastconﬁned toa virusinfected cell.Once phosphorylated tothe

triphosphate bycellular enzymesthe lattermolecule inhibits, againspeciﬁcally,

the functionof the herpesvirusDNA polymerase andhas no effecton cellular

DNA polymerases. It is both an inhibitor and a substrate of viral DNA

polymerase competing withGTP and being incorporated into viralDNA. It

has little or no effect against cellular DNA polymerase. New herpes DNA

elongation isaborted very successfully becauseaciclovir lacks the 3’hydroxyl

group on the sugar ring required for phospha te–sugar linkage and hence

addition ofnew bases and henceDNA chain elongation.

However, alatently infectedcell cannot becured andthus aciclovirdoes not

eradicate herpesvirusfrom aninfected individual, butit canbe usedto prevent

clinical recurrences. The compound has proved to be remarkably safe in

clinical practiceand somepatients havetaken thedrug orally(daily) forseveral

years. Infact inseveral countriesin theEuropean Community, aciclovircan be

purchased as an ‘over-the-counter’ drug for self-prescription for cutaneous

HSV infection,as with cold soresaround the mouth.

Another nucleoside analogue closely relat ed to aciclovir and called

penciclovir is widely used in clinical practice, withan advantage that fewer

dailydoses are required.As withthe prodrugvalaciclovir, aprodrug ofthe new

molecule has been introduced called famciclovir (Figure 4.4). This prodrug

may alsohave clinical usefulness againsthepatitis B virus.

AMANTADINE, AN M2CHANNEL BLOCKER OF

INFLUENZA A VIRUS

This cyclic primary amine was discovered by chance as an inﬂuenza virus

inhibitor inthe 1960s. It hadin fact beensynthesized as a potentialexplosive

and notas abiological. Numerous clinicaltrials have shownthat prophylactic

administration as atablet given twice aday will prevent inﬂuenza A(H3N2,

H1N1 orH2N2) clinical infection in70–80% of individuals. Unfortunatelyit

has noinhibitory effectagainst inﬂuenzaB viruses whichare importantviruses

causing mortalityabout every fourthyear. Nervousness isthe main side-effect

noted inabout 8%of personsreceiving 200mg amantadineper daybut dosage

can be halvedto avoid these problems and stillmaint ainantiviral effects. A

very similar moleculebut with an extramethyl group attached (rimantadine)

has equivalentclinical activity but causesrather fewer side-effects.

Studies of the therapeutic use of amantadine in prisons , schools and

universitiesthrougho utthe worldshowed, perhapssurprisingly, thatif thedrug

was given after infection but within 24–48 hoursof the onset of symptoms

these resolvedmore quicklyand thenumber ofdays ofincapacity was reduced.

Thus therapeuticuse of adrug against arespiratory virus ispossible, and this

opportunity, unexpected at the time, has been exploited by the newer

antineuraminidase drugs.

Recommendations from a WHO expert group are that the anti-inﬂuenza

compounds should be used prophylactically where epidemiologic al

investigations showthe presenceof inﬂuenzaA inthe community.Prophylactic

use should continuedaily for up to4–5 weeks until theepidemic has passed.

Chemoprophylaxis isrecommended for ‘special-risk’groups, suchas over-65s,

some diabetics, and persons with chronic heart or chest diseases who have

either notbeen immunizedor whowish to receiveadditional protectionto that

of immunization, orthose being potentially exposedto virus infection before

vaccination has become effective (2–3 weeks). These members of the

community are at much higher risk of seri ous complications and death

following inﬂuenza than others. Clinicians now appreciate that amantadine

dosage must be carefully adjusted for elderly and frail individuals and

particularly thosewith kidney disease orurinary retention, inwhom the drug

could accumulate.A reduced dose of100 mgor lower daily isrecommended.

The mode of action of the drug is still the subject of research and the

principal viral target is the viral M2 protein. The M2 protein forms a

transmembrane ionchannel inthe virusand amantadinecan blockthis channel

much asa gatecan prevent accessto the entranceof a building.When theM 2

ion channelis functioning correctly itallows the passage ofhydrogen ions to

the centreof thevirus andhence acidiﬁcationwhen thevirus is beinguncoated.

Under the inﬂuence of the resulting lowpH inside the virus the M protein

dissociates fromthe viral RNA whichis then free toinfect the nucleusof the

cell. Allthese vital early stagesof viral uncoating areblocked by amantadine

when it sits in the ion channel and blocks off access for protons. It is no

surprise thatdrug resistance toamantadine occurs when mutationsin the M2

gene and subsequentamino acid substitutions in theM2 protein prevent the

binding ofthe molecule and hencestop its effectas a gate.

RELENZA AND TAMIFLU,INHIBITORS OF

INFLUENZA A ANDB NEURAMINIDASE

The new anti-inﬂuenza drugs have a signiﬁcant advantage compared with

amantadine of inhibiting both inﬂuenza A and Bvirus es.Relenza is rather

poorly absorbedafter oral dosing and hasto be administered bydry powder

inhaler, but Tamiﬂu may be administered by mouth. These two new drugs

could revolutionizethe way in whichinﬂuenza is managed inclinical practice

and therebyspeed patients’ access toeffective chemotherapy.

Both drugsbind to agroup of 11or so aminoacids in theacti vesite of the

NA enzyme.These amino acids areconstant in all currentinﬂuenza A andB

viruses and so the drugs inhibit all these viruses. Even previous pandemic

viruses suchas theGreat Pandemicof 1918have anear identicalactive siteand

are inhibited.Drug-resi stantmutants have been describ edbut to dateapp ear

less pathogenicand less infectiousthan the wild-typevirus and therebywould

not beexpected to spread inthe community. Althoughresearch is continuing

with anti-common colddrugs none to datehas shown strong enoughclinical

effects towarrant extensive useand virtually no drugsexist for theremaining

important respiratory viruses, namely adenoviruses, parainﬂuenzaviruses or

coronaviruses.

A nucleoside analogue,ribavirin, originally researched asan anti inﬂuenza

drug islicensed to treatchildren withsevere respiratory distressafter infection

with respiratorysyncytial virus, but thenecessity of anaerosol apparatus not

unnaturally hasrestricted the usefulness ofthe drug.

ZIDOVUDINE AND DIDEOXYNUCLEOSIDEANALOGUES AS

ANTI-RETROVIRUS DRUGS

Within 2years ofthe isolationof theAIDS virus aseries ofpromising antiviral

compounds had been discovered and zidovudine had been shown to be

effective inprolonging the lifeof AIDS patients.The drugis rapidly absorbed

after oraladministration with ashort 1 hourhalf-life and sothe drug isgiven

two or three times daily. The ﬁrst double-blind placebo-controlled trial of

zidovudine inAIDS patients had tobe stopped and thecode broken when it

wasfound that virusinduced lethalityin thezidovudine-treated groupwas only

one comparedwith 19 in thecontrol group ofapproximately 194 patients. In

addition, fewer opportunistic infections developed in the zidovudine-treated

group, and a reduction in the level of circulating viral p24 core antigen

indicated a speciﬁc antiviral effect of the compo und. Zidovudine is now

considered tobe usefulfor prolongingthe lifeof thesepatients forup to 1year,

but itsuse is enhancedby drugcombinat ions.The originalsevere problems of

toxic effects of the drug on bone marrow cells necessitating transfusion in

approximately one-third ofthe patients have been overcome bothby dosage

reduction and useearlier in the diseasewhen the patient is stillﬁt. However,

headaches, nausea and insomniaare not uncommon side-effects of the drug

and thepatients have to becarefully monitored.

Zidovudine andthe otherdideoxynucleoside analogues arepotent inhibitors

of viral reversetranscriptase and hence DNAsynthesis and like aciclovir are

able to prevent chain elongation by, in the case of zido vudine, the 3’

positioning of theazido group. Therefore once thedrug is incorporated into

the newly growing viral DNA stra nd the essential phosphodiester–diester

linkage enablingthe nextnucleotide to beadded to thegrowing DNAch ainis

blocked. The dideoxynucleoside monophosphate is phosphorylated to the

triphosphate, by cellularenzymes, and the triphosphatedifferentially inhibits

the viral reverse transcriptase enzyme and has lesser effects on the cellular

DNA polymerase. Unfortunately the phosphorylation to the activetriph os-

phate occursnot only in virus-infectedcells but also innormal cells, and this

explains the side-effects of the drug. In contrast, as we have noted above,

aciclovir triphosphateis only present inherpes-infected cells.

A numberof dideoxynucleosidean alogues(ddI, ddC,3TC, D4T) havebeen

clinically evaluated and although they all exert antiviral effectsnevertheless

they also have side-effects, eachspeciﬁc to the compound in question. Also

effective are non-nucleosideanalogue inhibitors of viral reverse transcriptase

andparticularly inhibitors ofother viraltarget enzymessuch asprotease. Work

has also commenced to ﬁnd drugs tointeract with important viral proteins

such as integrase and regulatory proteins which control the speed of viral

replication,su chas Revand morerecently fusionfunctions ofthe gp41 portion

of thespike protein.

Non nucleosideand protease inhibitors forHIV

Most importantly, combination chemotherapy with other dideoxynucleoside

inhibitors (ddC, ddI, 3TC, D4T), or alternatively with non-nucleoside RT

inhibitors such as nevirapineor viral protease inhibitors (saquinavir) is now

widely used in AIDS patien ts to reduce the chance of drug resistance

(HAART). Currently there is some conﬂicting evidence from clinical trials

whether zidovudineand drugcombinat iontherapy shouldbe used earlyin the

disease in asymptomatic patients or whether it shouldbe reserved until the

patients beginto show early clinicalsigns of immunosuppression.

THE MOST RECENTPAST AND THE FUTURE

Arguably themost importantchemotherapeutic advancesin thelast yearshave

been in the treatment ofAIDS patients with drug combinations (HAART).

Combination chemotherapy has now becomethe accepted clinical approach

withHIV and willbe rapidlyextended toinclude newdrugs andmay beused in

cases of chronic hepatitis B and C infection and inﬂuenza. Undoubtedly a

clinical breakthrough has been the development of the two prodrugs,

valaciclovir and famciclovir, to treat herpes infections. Fortunately drug

resistance is not likely to be a major problem with herpesviruses. Two

important antineuraminidasedrugs against inﬂuenzahave been licensedand a

further two compounds are in development. These new possibilities in the

clinical management of inﬂuenza have led to a renewedinterest in the ﬁrst

antiviral, amantadine.

There alsoremain some very importanttarget viruses against whichfew, if

any, antiviralsexist. Thus, the eight hepatitisviruses all cause seriousdisease

whilst we now appreciate that the neglected papillomaviruses could be an

important causeof skin cancer. Newherpesviruses continue tobe discovered,

whilst only HHV1 and 2 are signiﬁcantly inhibited by the existing drugs.

Threatsof bioterroism willlead toevaluation ofdrugs againstsmallpox suchas

cidofovir and againstviruses which cause haemorrhagic feverssuch as Lassa

and Ebola. Inﬂuenza has recently been added to the list of potential

bioterrorist viruses.

Scientiﬁcally, major drug discoveries are most likely to emerge from a

judicious mixture of biology and X-ray crystallography whereby existing

compounds areclosely analysed for theirbinding or targetinteractions at the

molecular level. Already this approachhas led to the reﬁnement of the two

drugs bindingto inﬂuenza Aand B neuraminidase, proteaseinhibitor of HIV

and a drug against the common cold virus. Virologists are antic ipating a

new inﬂuenza pandemic and therefore antivirals with a bro ad antiviral

spectrum wouldbe comfortingto have. Amantadineitself does inhibitmost, if

not all,of the inﬂuenzaA subtypes knownto exist inhumans, birds, pigsand

horses andso might be expected toinhibit even a newpandemic inﬂuenza A

virus. The new neuroaminidase inhibitors would also act against pandemic

inﬂuenza Avirus.

Four decades ago the discovery of what we now recognize as important

cytokines, aand b interferon,led to over-hasty conclusionsthat viruses could

be conquered bythese broad spectrum molecules. Interferonscontinue to be

carefully investigatedas potentialinhibitors of hepatitisB andC viruses, often

in conjunctionwith speciﬁc antiviralssuch as ribavirinand famciclovir, andif

successful inthis role may yetfulﬁl their earlypromi se.

There will be occasional major setbacks, but antiviral chemotherapy like

other clinical-based sciences will continue to beneﬁt from exciting scientiﬁc

discoveries, new clini caladvances and further knowledgeof the pathology of

disease.

IS THEREA BETTER WAY?

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

5. VIRUS VACCINES

Lat. vacca¼ cow;vaccinia ¼cowpox.

L. R.Haaheim and J. R.Pattison

THE GLORIOUS PAST.. .AND THE NEWCHALLENGES

The global eradication of smallpox stands as a landmark in the history of

immunization. An intense combined internati onal effort, The Smallpox

Eradication Programme of 1967 organized through the World Health

Organization (WHO), led to the complete elimination in 1977 of one of

mankind’s great scourges. A long time had passed since Jenner in l796

successfully inoculateda farmer’s boywith pustule materialfrom a dairymaid

suffering from cowpox (see illustration to Chapter 41). Additional achieve-

ments duringthe 20th century havebeen the introduction ofmany new virus

vaccines, e.g. polio, measles,rubella, mumps, rabies, yellow fever, inﬂuenza,

varicella and hepatitisA and B. Vaccines against e.g.adenovirus, cytomega-

lovirus, herpessimplex virusand rotavirusare currentlybeing developedor are

under clinicaltrials.

Great optimism followed the successful smallpox programme, butnot all

infectious diseases of viral aetiology may be so amenable to control. In

particular, avaccine againstHIV may bemore difﬁcultto develop thanat ﬁrst

anticipated. Nevertheless, there is a range of virus diseases within reach of

being controlledby vaccinationat leastin developed countries.Poliomyelitis is

for all practical purposeseliminat edfrom many countries through extensive

use ofeither live (attenuated) orkilled (inactivated) vaccines amongchildren.

In some developed countries measles is now close to eradication or is an

extremely rare disease,and through continued mass vaccination mumps and

rubella mayalso becomeinfections of thepast. Onthe other hand,inﬂuenza is

difﬁcult to control by vaccination since the virus changes its antigenic

properties andpreviously acquiredimmunity becomesobsolete. Itmay be even

more difﬁcult to control such illnesses as the common cold because of the

multiplicity ofvirus esinvolved. For example, thereare over 100 serotypesof

rhinoviruses andthese are difﬁcult toreplicate in thelabo ratory.

It isnotable that those virusinfections which have been wellcontrolled by

immunization are systemic infections in which a viraemia is an essential

component ofthe pathogenesisof thedisease. Much greaterdifﬁculty hasbeen

experienced in developing effective vaccines against superﬁcial mucosal

infections of the respiratory and gastroint estinal tracts and against those

diseases inwhich the virusremains largely cell-associated.This latter problem

may wellapply to the developmentof HIV vaccines.

ACTIVE IMMUNIZATION

Vaccines are preparations, administered either orally or parenterally, which

stimulate a protective speciﬁc immune response in the recipient without

themselves causingdisease. Withsome vaccines (e.g.hepatitis B)it isnecessary

to add an adjuvantwhich non-speciﬁcally potentiates the immune response.

Adjuvants, usually aluminium salts, can also delay the release of vaccine

material fromthe injection site. Inprinciple there aretw omain types ofviral

vaccines available, namely the attenuated live virus vaccine and the non-

replicating (‘killed’)variety. Inthe ﬁrst instancevirus ismanipulated in vitroto

be of low virulence but able to replicate in the vaccinee and stimulate the

desired protective immune response without causing disease. In the case of

non-replicating vaccines the virus may be replicated in an appropriate

laboratory system, e.g.cell culture or embryonated eggs, puriﬁedand ﬁnally

inactivated (‘killed’) by chemical means (usually formalin). A further

reﬁnement of the inactivated vaccine is to split the virions by means of

detergents, orto isolatethe desired viralsubunits tomake up theﬁnal vaccine.

Hepatitis Bvaccine is non-replicatingand obtained by theexpression in yeast

of clonedviral genes.

To date, emphasis has been placed on live virus vaccines except where

laboratory replication has not been possible (hepatitis B) or satisfactory

attenuation hasnot beenachieved (rabies). Lessantigenic massis requiredin a

live virusvaccine since there isreplication and build-up ofimmunogen in the

vaccinee. As a consequenceinactivated vaccines are usually more expensive.

Live virus vaccines induce long-lasting immunity after a single dose (live

poliovirus vaccine requires threedoses to ensure protection against all three

types); killed vaccines often require multiple doses. Live virusvaccines also

have theirdrawbacks. Throughthe manufacturing processadventitious agents

may be incorporated. Attenuated vaccinestrains may revert to virulence on

passage through the human host. Neither of these problems have proved

signiﬁcant in practice. Finally, attenuation is judged in immunocompetent

individuals, therefore live vaccines are often contraindicated in immuno-

compromised individualsand also during pregnancy.

It is generally believed that complete protection against infection is

extremely difﬁcult to obtain by vaccination, or at least not for any long

period of time post-vaccination. The initial hope for a HIV vaccine was

precisely that: to confer completeprotection (sterilizing immunity) and thus

arrest thevirus at the siteof entry. Thismay indeed be aformidable task.

However, there isabundant evidence that manyvaccines elicit an excellent

protection against disease. Thus, the actual infection may take place, and

possibly generate a beneﬁcial booster immune response. The infection will

nevertheless be quickly aborted due to the immunological recall of the

vaccine-induced memory, and/orbecause of some level of pre-existingactive

immunity notnecessarily located atthe site of viralentry. A goodexample of

such acase is the use ofinactivated poliovaccines that insome Scandinavian

countries hasmanaged to eliminatepoliomyelitis, even if thepost-vaccination

intestinal immunityhas been low orabsent.

PASSIVE IMMUNIZATION

So farwe havespoken only ofactive immunization, butpassive immunization

also has a place in preventing virus infections. Passive immunization is the

transfer to oneindividual of antibodies formed inanother. The advantage is

that itis rapid inonset (effective withina day), but ithas the disadvantageof

being short-lived(lasting only 2–6months) since theinjected foreign antibody

decays with ahalf-life of 21 days. Human immunoglobulin preparationsare

madeof donated bloodthrough aseries offractionation steps.If theyare made

from unselectedblood donorsthe preparationwill berich inspeciﬁc antibodies

that arecommon in thepopulation. Hyperimmune globulinsare made froma

pool of unitsof blood selected because theyhave a high titre ofa particular

antibody. Such preparations are available forthe prevention of hepatitis B,

rabies andchickenpox.

In certainsituations (rabies,neonatally acquired hepatitisB) itis possible to

combine active and passive immunization and take advantage of the best

features ofeach, theimmunoglobulin giving immediateprotection untillasting

active immunityfrom vaccination develops.

ADMINISTRATION OF VACCINES

The route of administration depends on the vaccine. Live polio vaccine is

always given by mouth. Injectable vaccines are usually administered intra-

muscularly ordeep subcutaneously, although an equallyeffective but smaller

dose can sometimes be given intradermally and this may be relevant with

expensive vaccines(e.g. rabies).

Since vaccination usually requires attendance at a clinic it is often

worthwhile giving more thanone vaccine at a visit. Individualscan respond

to multipleantigens administered simultaneously, althoughbetween 4 and 14

days afterone vaccine individuals may respondpoorly to another. Therefore

vaccines shouldeither be givensimultaneously, preferably atdifferent sites, or

after aninterval ofat least3 weeks.If multiple dosesare requiredthe optimum

interval will depend on which type of vaccine (live or killed) is used. It is

1 month between doses of polio vaccine and 1 and 4 months, respectively,

between the ﬁrst and second andthe second and third doses of hepatitis B

vaccine. However, intervals may vary and the reader is advised to consult

national regulations.

SIDE-EFFECTS AND COMPLICATIONS

It is important to remember that tri vialside-effects are quite common with

viral vaccines.These are most oftenlocal pain, redness andinduration at the

injection site. Less frequent are systemic effects such as fever, malaise,

headache, arthralgiaand nausea.With somelive virusvaccines such asmeasles

and rubella mild symptoms and signs resembling the natural disease may

occur.

Serious complications are extremelyrare, but they do occur; for example,

paralytic poliomyelitis followingthe use of liveattenuated polio vaccine, and

encephalitis following yellow fever vaccination in infants. Note that it is

important to adhere to the manufacturer’s/health authority’s list of contra-

indications cited for each vaccine in question so that the risk of allergic

reactions orother preventable complications canbe minimized.

Immunosuppression isa contraindication foruse of livevaccines. However,

different countries are adapting different strategies for theimm unizationof

HIV-positive children depending upon therelative risk of side-effects of the

vaccine and danger from thedisease being immunized against. As a rule, it

appears that asymptomatic HIV-infected individuals can be offered virus

vaccines.

EPIDEMIOLOGICAL CONSEQUENCESOF MASS

VACCINATION

If an individual beneﬁts frombeing immunized it is often assumed that the

overall effect on society at large will be equally beneﬁcial. This may not,

however, alwaysbe thecase. Thereason forthis isthat weare changingaspects

of herdimmunity andit may notbe possibleto precisely anticipatethe shiftof

susceptible cohorts. Deferring childhood diseases to older age groups may

consequently increasethe frequencyof complications ifthe vaccinecoverage is

too low(e.g. measles).

A specialcase is theuse of rubellavaccine: if onlya low butstill signiﬁcant

fraction ofchildren and teenagersis immunized, thereis apossibility, through

the consequent reduced spread of wild-type virus in the community, of

accumulating more susceptiblewomen at childbearing age,and thus possibly

increasing theincidence of congenital rubellasyndrome.

Another special case is the selective useof inﬂuenza vaccines among risk

groups aimed at reducing morbidity and mortality among these individuals

rather thanattempting to eliminatethe virus from society. Indeed,eradicating

inﬂuenza through mass vaccination is for many reasons believed to be

impossible.

To avoidepidemiological backlashit is formany vaccinesoften necessaryto

achieve veryhigh (490%)rates ofimmunization. Thiscan onlybe donewith a

high levelof acceptanceby the community,combined withgreat efforts onthe

part ofthe health care systemand its ofﬁcers.These factors are oftenpresent

when manycases ofa seriousdisease occur,but interest tendsto waneonce the

disease becomes rare. The public at large will then inevitably focus on the

possible side-effectsand complications ofthe vaccine preparationitself, rather

than the morbidity and mortality that the disease would cause in an

unprotected society. With time, the public will forget the effect that these

diseases hadon healthand welfare,and theremay bean increasedtendency for

doctors and health workers to grant exemption, thus reducing vaccine

coverage. Some concernhas been raised claiming thatthe discontinuation of

smallpox vaccination leaves the world susceptible to reintroduction of

poxviruses from unrecognised animalreservoirs .And similarly, an immuno-

logically virgin global population could inviteterrorist threats or the actual

release ofvariola virus procured fromillegal stocks of virus.

Another caseis theeventual eliminationof measles virusand thesubsequent

end to measles vaccination programmes. The consequential wanin g and

disappearance ofherd immunity may allow caninedistemper(-like) viruses to

be introducedfrom animal reservoirs.

In order to maintain a high immunization rate over the years it is of

paramount importance to continuously inform the public and the health

professions alike of both the individual and community beneﬁts of well

designed andimple mentedmass programmes of immunization.Failure to do

so will inevitably lead to a reduced coverage, the accumulation of new

susceptibles thuspaving the way fornew outbreaks.

THE FUTURE

Considering the glorious past it is tempting to postulate an equally bright

future for vaccinesand vaccine programmes, especially since modernscience

and technology seem to advance at such high pace. But even today’s

technology has not been fully exploited. It is assumed that within a few

years both polio and measles may become extinct as human diseases. This

ambitious globaleffort is directed bythe WHO.

Modern sciencehas provideda betterunderstan dingof theﬁne structuresof

virus particles, thus allowing the identiﬁcation and subsequent large-scale

production ofthe mostuseful partsof theinfectious agentfor vaccineuse. This

methodology has nowbee n put to good practical use forthe preparation of

hepatitis B vaccine using cloned DNA expressed in yeast cells to produce

HBsAg. This was a giantleap from the earlier method of purifying HBsAg

from theblood of hepatitis carriers.

Other strategies being investigated are the use of synthetic oligopeptides

covering importantepitopes onthe virus or peptides masqueradingas epitopes

(‘mimotopes’). However,since the immunogenicityof manysuch preparations

may fallshort ofthe ideal, thesestrategies wouldrequire new andmore potent

adjuvants than are currently inuse, as well as safe carrier molecules. Other

approaches include investigating ways of stimulating mucosal immunity by

targeting vaccine material to mucosal epithelium, or using biodegradable

microspheres thatcan releasevaccine materialin acontrolled way.Possibly the

most promisingand certainly daring strategyis to inject‘naked’ DNA, in the

form of anon-replicating plasmid coding forselected viral proteins, into e.g.

muscle tissueof the vaccineeand let theinjected DNA codefor proteins inan

authentic form to beproperly presented on MHC molecules. Thisapproach

will in many waysmimic the process of a viral infection andthus stimulate

both humoral and cell-mediated immunerespo nse.For manufacturers these

modern methodsavoid large-scaleproduction ofpotentially harmfulinfectious

agents.However, clinical trialsso farhave notlived upto itspromises. Another

unexpected strategyis thelarge-scale production ofviral proteins inplant cells

(‘edible vaccines’).

Many otherquestions need to beaddressed:

. Which arethe most cost-eﬀective waysof vaccine production anddelivery?

. How canwe improve vaccinestability and storage,especially inthe tropics?

. Can we reduce the number of visits tohealth clinics by developing more

multivalent vaccines?

. Can reliablemethods of time-controlled slowrelease of vaccinematerial be

developed, ensuring bothpriming and booster dosesat a single visitto the

clinic?

. More eﬀective adjuvants and vaccine vehicles should be developed.

Especially important are designed molecules that can ensure uptake by

epithelial cellsat the mucosal linings.

. How cana more potent mucosalresponse be stimulated?

. How canwe ensure better long-termimmunological memory?

. How can we more eﬀectively stimulate CTL response for inactivated

vaccines?

. Using ‘naked’DNA asvaccine material,can weensure thatno integrationof

the injectedDNA occurs andthat no adverseimmunological reactions take

place throughprolonged antigenic stimulation?

Both scientiﬁc andtechnical progress is needed,but equally important isa

well-structured community health service and public motivation to take

advantage ofthe many excellent vaccinesalready available. See Table5.1.

Table 5.1 SOME CURRENTLYAVAILABLE VIRUS VACCINES

Vaccine Nature Route** Timing

Polio Live attenuated

Inactivated

Oral

s/c ori/m

Infancy/childhood

Similar (orwhen live

vaccine iscontra-

indicated)

Measles* Live attenuated s/c or i/m Infancy/childhood

Mumps* Live attenuated s/cor i/m Infancy/childhood

Rubella* Live attenuated s/cor i/m Infancy/childhood/

adolescent girls,

susceptible women

post-partum

Inﬂuenza Inactivated s/cor i/m Theelderly and those

with certainchronic

diseases

Hepatitis A Inactivated i/m Travellers, occupational

exposure

Hepatitis B Inactivated i/m High-risk groups,

occupational exposure

Rabies Inactivated s/c,i/m or i/d Occupationalexposure,

post-exposure

treatment

Yellow fever Live attenuated s/c Travellers

Japanese

encephalitis

Inactivated s/c Travellers

Tick-borne

encephalitis

Inactivated i/m Travellers

Varicella Live attenuated s/c Immunocompromised

Vaccinia Live i/d Laboratory workers

handling smallpox

virus

*Availablein combination asMMR vaccine.

**s/c,i/m, i/dstand forsubcutaneous, intramuscular andintradermal, respectively.

ENTEROVIRUS TRUNKROUTES

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

6. ENTEROVIRUSES: POLIOVIRUSES,

COXSACKIEVIRUSES, ECHOVIRUSES

AND NEWER ENTEROVIRUSES

Gr. enteron¼small intestine, themain replicationsite for mostenteroviruses.

A.-L. Bruu

The Enterovirus genus ofthe picornavirus family is a large group ofviruses

associated witha spectrum ofdiseases ranging from paralyticpoliomyelitis to

mild, non-speciﬁc febrile illness and rarely associated with disease of the

gastrointestinal tract.They are worldwide indistribution but more than90%

of infectionswith enteroviruses are subclinical.

The Enterovirus genuscomprises several subgroups of whichthe following

may causedisease in humans:

. Polioviruses (types 1–3).Gr. polios¼ gray, myelos¼marrow.

. Coxsackieviruses, Group A (types 1–22, 24 ) and Group B (types 1–6).

Coxsackie is the village in theUSA where the patients from whom these

viruses wereﬁrst isolated lived.

. Echoviruses(types 1–9,11–27). Entericcytopathogenichuman orphanviruses,

originally considerednot tobe associated (‘orphan’)with humandisease.

. Newer enteroviruses(types 29–34, 68–72).Human enterovirus 72is hepatitis

A virus,see Chapter 24.

The enteroviruses havea diameter of 24–30nm, anicosahedra lstructure and

consistof 60 subunits,each containingone setof thestructural proteinsVP1–4.

The single-strandedRNA has positive sense(mRNA function). Thecomplete

nucleotide sequencehas been determined forthe polioviruses and someother

enterovirus types. Some enteroviruses may cross-react to a certain degree,

mainly dueto determinants on VP1.

Clinical syndromesfrequently associated withspeciﬁc typesof enteroviruses

include thefollowing:

. Paralytic disease: polioviruses.

. Herpangina: coxsackie Aviruses.

. Hand, footand mouth disease: coxsackieA virus (A16).

. Epidemic myalgia/pleurodynia: coxsackieB viruses.

. Generalized disease inthe newborn: coxsackieB viruses.

. Myocarditis/pericarditis: coxsackie Bviruses.

. Conjunctivitis: enterovirus 70.

. Fever andrash: echoviruses especially.

. Meningitis: many en teroviruses.

1400BC EGYPTIAN STELE SHOWING PRIEST WITH ‘HORSE-FOOT’.

POLIOMYELITIS? (Courtesyof Ny CarlsbergGlyptotek, Copenhagen)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

7. POLIOVIRUSES

Infantile paralysis;acute anterior poliomyelitis; Ger.Kinderla

hmung.

A.-L. Bruu

Poliomyelitis is an acute infectious disease with or without signs of CNS

involvement.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

The infectionis spreadby thefaecal–oral route. The incubation periodis

usually 1–2weeks. The patientcan infectsuscep tiblepersons fromsome

days beforeillness andfor oneto severalweeks after theillness. Children

are infectiousfor a longer periodthan adults.

SYMPTOMS AND SIGNS

Systemic: Fever, Headache,Myalgia, Nausea, Vomiting

Local: Signs of Meningitis, Pareses

About95% of infectionsrun asubclinical course.Patients sufferingfrom

aseptic meningitis will recover in 1–2 weeks.Paralysis often results in

persistent lameness.

COMPLICATIONS

Respiratory failure, obstruction of airways, involvement of the

autonomic nervoussystem.

THERAPY AND PROPHYLAXIS

No speciﬁc therapy,immunoglobulin is of no practical value.Vaccine,

either attenuatedor inactivated, gives morethan 90% protection.

LABORATORY DIAGNOSIS

Demonstration ofpoliovirus inthroat swab orin faecalsample collected

in the acute phase of the disease, viral RNA in faecal sample, and

poliovirus IgMantibodies or IgG antibodyrise in paired sera.

Figure 7.1 POLIOVIRUS (PARALYTICPOLIOMYELITIS)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

The incubationtime of poliomyelitis isusually 7–14 days,but may vary from

4 to morethan 30 days. The diseasetypically starts with a prodromalpha se

of a few days’ duration. The patient has fever and complains of myalgia.

Constipation is a common feature. This phase (‘minor disease’) is usually

followed byan interval of afew days whentemperature becomes normal and

the patient seems torecover. The temperature then increases again with the

development of paralysis and frequently also aseptic meningitis. Such a

biphasic courseis especially commonin children. Thesecond phase isinitially

characterized byhyperirritability and increased tendonreﬂexes. This maylast

from several hours toa few days, leading to theparalytic stage with loss of

tendon reﬂexes. The paralysis is ﬂaccid and most frequently affects the

extremities, but any voluntary muscle (group) may be involved. The

development of paralysis may take some hours or a few days. During the

initial phase of the paralytic stage the patient may also exhibit sensory

disturbances. Strenuous exercise, injections (vaccination), operations (tonsil-

lectomy) andpossibly also pregnancymay increase theincidence, severity and

site of paralyticdisease. Bulbar poliomyelitis may occuralone (in about 10%

of all patients with paralysis) or as a mixed bulbospinal form. This

localization may lead to involv ement of cranial nerves with paralysis of

pharyngeal muscles and dysphagia, and of respiratory muscles followed by

dyspnoea. Bulbar involvement is often accomp anied by lesions of the

respiratory andcirculatory centres leading torespiratory failure, fallin blood

pressure andcirculatory shock. The lethality ofthis condition varies between

20 and 60%. The CSF often shows normal values, but an increase in cell

count up to a few hundred/ml is sometimes seen. Polymorphonuclear cells

may be prevalent in the very beginning of the disease, but are soon

outnumbered by lymphocytes. Slightincrea sein the protein content may be

seen. Immunityafter poliovirus infection,whether asymptomatic or paralytic,

is type-speciﬁcand lifelong.

The most important differential diagnosis is polyradiculitis (Guillain–

Barre

syndrome), where the pareses are ascending and symmetrical

combined with a variety of sensory disturbances. The CSF shows a rather

high protein content with no or only slight increase in cell count. Other

diseases which may mimic poliomyelitis are acute transverse myelitis, tick-

borne encephalitis and reduced mobility due to arthritis and osteomyelitis.

The diagnosis of poliomyelitis is based upon the development of

asymmetrical pareses in the course of some hours to a few days withlittl e

or no sensory loss.

CLINICAL COURSE

Fever and general sympt oms last for 1–2 weeks. The paralysis reaches a

maximum within 2–3 days. More than 50% of cases recover during the

subsequent weeksor months. Theremaining patients willsuffer from residual

deﬁcits inone ormore muscles.The overalllethality ofpoliomyelitis hasbeen 5

to 10%,but is substantially reducedby maintaining patients inrespirators.

COMPLICATIONS

Encephalitis and myocarditis may occur during the acute stage (see bulbar

poliomyelitis). A post-poliomyelitis syndrome is observed in some 25% of

survivors of paralyticpoliomyelitis. After several decadeswith no changes in

their clinicalcondition, theydevelop newweakness, painand fatigue.Thi s may

bedue to adenervation ofinitially reinnervatedmuscle ﬁbres,but theaetiology

is notclear. Thesepatients arenot excreting poliovirusand arenot contagious.

THE VIRUS

Poliomyelitis iscaused byone ofthe three typesof poliovirus(Figure 7.2). The

virion isnaked and hasa diameter of28 nm.It contains single-strandedRNA

of positive polarity (mRNA)within a protein shell (capsid) composed of 60

capsomeres. Thecapsid isbuilt upof four proteins,VP1–4. Virusreplication is

initiated byRNA transcription intonega-

tive strands to act as templates for new

viral RNAs.From the viral RNAa large

polyprotein ismade, whichlater iscleaved

to generatethe capsidproteins VP1–4and

a rangeof other proteins. Final assembly

of new virions takes place in the cyto-

plasm. There are some minor antigenic

cross-reactions between some entero-

viruses. Even though the three serotypes

of poliovirusshare someantigenic proper-

ties, in particularbetween types 1 and 2,

they are characterized by marked inter-

typic differences.The epitopesresponsible

for inducing neutralizing antibodies are

located on the three structural proteins

VP1, VP2 and VP3 of the viral capsid,

VP1 being the major immunogen. For

differentiation between the three types, type-speciﬁc antisera prepared by

cross-adsorption with heterologoustypes, or suitable monoclonal antibodies,

are used. However, the capsid proteins induce a mainly speciﬁc immune

response during aninfection and after vaccination.All three polioviruses are

highly cytopathic to many primary cell cultures and permanent cell lines,

Figure 7.2 POLIOVIRUS.

Bar, 50nm (Electron micro-

graph courtesy of E. Kjelds-

berg)

causing cell death without changes in cell morphology typical of entero-

viruses. Poliovirusesare stable atpH valuesbetween 3 and9, resistant tolipid

solvents and ratherslowly inactivated at room temperature. Becauseof this,

the virus mayremain infectious for several days in water,milk, food, faeces

and sewage.

EPIDEMIOLOGY

Poliomyelitis hasprobably beenwith usfor centuries.However, itwas notuntil

the later part of the nineteenth century thatthe disease was described as a

separate clinical entity. Duringthe ﬁrst half of the twentiethcentury several

large epidemicsof poliomyelitis wereobserved in Europeand North America.

Thediseas ewas thenmost frequentamong youngchildren, butin thelater part

of theperiod it becamemore common among olderchildren and adolescents.

This was most probably due to improved hygienic conditions reducing the

possibilities forfaecal–oral spread. In countrieswith a temperate climate,the

disease ismainly seenduring summer andautumn months,whereas in tropical

and subtropical climates poliomyelitis is prevalent throughout the year and

most oftenoccurs in small children.The introduction ofpolio vaccines in the

1950s hasled to more or lesscomplete eradication of poliomyelitisin several

countries, especially in Europe and North America. Due to vaccination

programmes of small children, most clinical cases are now found among

unvaccinated infants, older children and adults.It is therefore important to

maintain ahigh vaccinationcoverage rate(490%) to accomplisha sufﬁciently

high degree of herd immunity. Com placency in adhering to vaccination

programmes invariably leads to cluster outbreaks of poliomyelitis from

imported caseswhen herd immunity incertain regions or communitiescomes

under acritical limit. In1988 the 41stWorld Health Assemblycommitted the

World HealthOrganization and hadset to target theyear 2000 asthe year of

global eradicationof poliomyelitis. This goalwill probably be reachedwithin

the nextfew years.

THERAPY AND PROPHYLAXIS

There is no speciﬁc treatment for poliom yelitis. Impairment of respiratory

function may necessitate artiﬁcial respirati on. Physiotherapy as early as

possible is important in preventing or reducing lasting sequelae. Although

improved sanitationand hygienehelp tolimit thespread ofpoliovirus, theonly

efﬁcient meansof preventing paralyticpolio is throughwidespread immuniza-

tion. Two types of vaccine are available against poliomyelitis, inactivated

vaccine (IPV, Salk) and live attenuated oral vaccine (OPV, Sabin). Both

vaccine formulationscontain all three poliotypes.

OPV is the mostwidely used vaccine for prevention ofpoliomyelitis. It is

composed of attenuated strains of the three poliovi rus types, and is

administered orally. At least twoor three doses are considered necessary to

ensure adequateimmunity, insome countrieseven ﬁve tosix ormore dosesare

given inthe primary course.Revaccinat ion is used toa varying degree.A full

primary course inducesan antibody response against all threetypes in more

than 90% ofvaccinees and gives ahigh degree of protection againstdisease.

OPV also induces intestinal immunity due to pro duction of secretory IgA

antibodies. This is important for inhibition of virus replication in the gut,

diminishing thepossible spreadof virus tosusceptible contacts. OPVis almost

non-reactogenic, and is very safe. However, in a few cases an attenuated

vaccine strainmay induce paralyticdisease. This occursin about onecase per

1–10 millionvaccine doses administered.

IPV was the ﬁrst vaccine usedagainst poliomyelitis. It contains the three

types of poliovirus inactivated by formaldehyde and is administered

parenterally. The use of IPV in the late 1950s was followed by a 90%

reduction ofpoliomyelitis caseswhen it wasreplaced in manycountries bythe

more easily admini stered OPV around 1960. Newer IPVs have higher

immunogenic potency which has led to a reintroduction of IPV in many

developed anddeveloping countries.The primary vaccinationcourse with IPV

consists oftwo orthree doses,usually followed byrevaccination afterintervals

of about 5–10 years during childhood and adolescence. Some countriesare

using acombination of OPV andIPV.

LABORATORY DIAGNOSIS

Recommended methodsfor laboratory diagnosis ofpoliovirus infection are:

. Virus isolation from faeces and throat washings by inoculation into cell

cultures. The presence of poliovirusis shown by degeneration of cultured

cells withina few days. Theresult of conventional typingby neutralization

will requireanother coupleof days. Alternativelyimmunoﬂuorescence using

monoclonal antibodies canbe used, allowing the distinctionbetween wild-

type virusand vaccine strains.

. Detection ofpoliovirus RNAin faecalsamples byPCR. This methodwill also

distinguish betweenwild strains and vaccinestrains.

. Antibody investigations. The method of choice is m-chain capture (IgM)

ELISA, which isspeciﬁc for each poliovirustype. Other antibody testsare

neutralization andCFT on paired serumsamples.

Thesamples should becollected asearly aspossible inthe courseof thedisease.

Children usuallyexcrete virus for1–2 weeks, adults fora shorter time.As the

excretion maybe intermittent during thelater phases of thediseas e, repeated

samples shouldbe collected.A negativeculture orno poliovirus RNAdetected

may notexclude infection,especially if thematerial istaken late inthe disease.

In suchcases, antibody investigations willbe useful.

AN ORPHANVIRUS LOOKING FORPARENTAL DISEASES

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

8. COXSACKIEVIRUSES,

ECHOVIRUSES AND ENTEROVIRUSES

29–34 AND 68–71

A.-L. Bruu

These enteroviruses may cause febrile diseases, in some cases with signs of

infection ofCNS, muscle, heart, skin,eye and respiratory tract.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Enteroviruses spread from personto person mainly by the faecal–oral

route, and to a lesser degree by the respiratory route. Some types

associated with conjunctivitisspread by direct contact. The incubation

period is5–14 (2–25) days.Enterovirus conjunctivitis has anincubation

period of12–24 hours.

SYMPTOMS AND SIGNS

General: Fever, Headache,Malaise

Neurological: Meningitis, rarely Encephalitisand Transient

Paralysis

Other: Epidemic Myalgia/Pleurodynia (Bornholm

Disease), Myocarditis,Pericarditis, Generalized

Disease inthe Newborn, Vesicular and

Maculopapular Exanthems,Haemorrhagic

Conjunctivitis

Usual durationis a few daysto about 1week.

COMPLICATIONS

Occasionally neurologicalsequelae.

THERAPY AND PROPHYLAXIS

There isno speciﬁc therapy,and no immunoglobulin orvaccine against

these enteroviruses.

LABORATORY DIAGNOSIS

Virus maybe isolated fromthe pharynxearly in thedisease, from faeces

for at least 1 week and in some cases from other sites of infection.

Enterovirus nucleic acid may be detected by PCR in faecal sample,

throat swab, vesicle ﬂuid, myocardial tissue, pericardial ﬂuid or in

cerebrospinal ﬂuid(CSF) for asepticmeningitis. Forantibody investiga-

tions them-capture ELISA is themethod of choice.

Figure 8.1 ENTEROVIRUS (SEROUSMENINGITIS)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

Like poliovirus the coxsackieviruses and echoviruses multiply primarily in

lymphoid tissuein the pharynx andthe small intestine. Inabout 5% of cases

virus mayspread toother targetorgans, the mainones beingthe meninges, the

brainand spinal cord,myocardium andpericardium, striatedmuscles andskin.

Infection leads tolasting type-speciﬁc immunity. Feverof short duration and

sometimes a rashor mild upper respiratory symptomsare the most frequent

clinical diseases.A few cases progressto one ofthe following syndromes:

Asepticmeni ngitis.In typicalcases abiphasic courseis seen.After aninterval of

1–2 days withfew or no symptoms, the temperaturerises again to 38–398C,

accompanied by headache, neck stiffness and vomiting. A non-speciﬁc

maculopapular rash, sometimes with petechial elements, may be seen. The

CSF is clearwith slight or moderateelevation of cell count (upto 500610

litre, mainlylymphocytes) andprotein content,but with normalsugar content.

The illnessmay lastfor 2–10days, sometimesfollowed bya convalescent phase

of rather long duration. The prognosis is good as most patients recover

completely. Meningoencephalitis orencephalitis may occur in somecases. In

differential diagnosis, meningitis caused by other viruses and early or

inadequately treatedbacterial meningitis which maymimic aseptic meningitis

should be considered. Note a petechial rash is also seen in meningococcal

disease. Lymphocytes are seen in the CSF (tuberculous, listerial and

cryptococcal meningitis),but usually the glucosecontent is lowered.

Complications aretransient paralysis and polio-likedisease.

Epidemic myalgia/pleurodynia (Bornholmdisease). This is apainful inﬂamma-

tion ofthe muscles, mostpronounced in theintercostal muscles orabdominal

muscles, accompanied bypain that may besevere (devil’s grip) and resemble

ischaemic heartdisease or ‘acuteabdomen ’.The pain isoften intermittent for

periods of2–10 hours, combinedwith rise intemperature. The illnesslasts for

4–6 days, but relapses in the following weeksa renot infrequent. Complete

recovery isthe rule.

Myocarditis/pericarditis. This isobserved in 5% ofpatie ntswith coxsackie B

virus infections. Typical features are fever, chest pain and dyspnoea. Other

signs arepericardial rub, heart dilatationand arrhythmias. Heart failuremay

occur. The illnessusually lasts for 1–2 weeks. Relapsemay occur during the

following weeks and months in 20% of patients. The most important

differential diagnoses arecardiac ischaemia, infarction andmyopericarditis of

other aetiology.

Neonatal myocarditis. Some enteroviruses, mostly coxsackie B3 and 4, may

cause a severe, often fatal disease ininfants characterized by sudden onset,

lethargy,tachyca rdia,dyspnoea andcyanosis. Itis asystemic infectionas many

organs (heart, brain, liver, pancreas) are involved. The virus is transmitted

from motherto child just beforeor at birth.

Herpangina. Theillness is seenmainly inchildren. Some 8–10vesicles or small

ulcers, 1–3mm indiameter, areseen on theposterior pharyngealwall. There is

painon swallowing andusually slightfever ofa fewdays’ duration.Differential

diagnoses areherpes simplex, varicella, aphthousstomatitis.

Hand, foot and mouthdisease. This occurs most often inchildren. Moderate

fever of38–398C maybe seen.Vesicles up to5mm in diameterare localizedon

the buccalmucosa and tongue aswell as onthe hands and feet.

Rashes. Maculopapular rashes (‘rubelliform’ or non-speciﬁc) are seen quite

frequently in coxsacki e A and echovirus infections, accompanied by

pharyngitis and fever. Arash is sometimes seen in the course ofmeningitis.

Differential diagnoses are erythema infectiosum, rubella, measles and rashes

seen inmeningococcal disease.

Acute haemorrhagic conjunctivitis. This eye disease is characterized by pain,

swelling of the eyelids and subconjunctival haemorrhages of a few days’

duration, usually healing spontaneously in less than a week. It is highly

contagious, with an incubation time of 12–24 hours, and spreads by direct

contact. Extensive epidemics havebeen observed in the Far East(caused by

coxsackie A type 24) and in Africa, Japanand India (enterovirus type 70).

Spreadis favoured bypoor hygienicconditions asin refugeecamps. Associated

neurological disease (radiculomyelopathy, cranial nerve involvement) occurs

rarely andmay lead to residualparalysis.

Coxsackie B has also been associated with idiopathic dilated cardiomyo-

pathy. Some studies haveshown evidence for a connection between juvenile

diabetes type1 and coxsackie Bvirus infection.

THE VIRUS

The enterovirus group(Figure 8.2) is oneg enusin the Picornaviridae family.

They aresmall (28nm), roughly sphericaland contain asingle-stranded RNA

molecule of positive polarity, which func-

tions as mRNA. The RNA is surrounded

by aprotein shell (capsid) withicosahedral

symmetry. All picornaviruses contain four

polypeptides, VP1–4, VP1being the major

immunogen. There is a certain degree of

serological cross-reactivity betweenentero-

virus types,especially between typeswithin

the samesubgroup, due to sharedepitope s

not exposed atthe surface of the virus, as

seen when using the complement ﬁxation

test. Enteroviruses retain infectivity at

pH3–9 and are resistantto several proteo-

lytic enzymes and lipid solvents. Theyare

stable fordays at roomtemperature. Inthe

laboratory, thecoxsackie Band echoviruses

will grow in several different cellcultures.

Figure 8.2 ECHOVIRUS

WITH ANTIBODY (Electron

micrograph courtesyof

E. Kjeldsberg)

The coxsackie B viruses willalso infect newborn mice. Coxsackie A viruses

replicate inmice, but only afew will doso in cell cultures.

EPIDEMIOLOGY

Man isthe only natural hostfor human enteroviruses. Thevirus replicates in

the upper and lower alimentary tract and is excreted from these sites.

Enteroviruses spread mainly by the faecal–oral route, and during theacute

stage alsoby therespiratory route. Theyhave a worldwidedistribution. Inthe

temperate zones spread takes place in the summer and autumn months, in

tropical andsubtropical zonesthroughout theyear. Children areinfected more

frequently than adults, and males somewhat more frequently than females.

Poor sanitaryconditions will favour spreadof these viruses.

THERAPY AND PROPHYLAXIS

There isat present noknown speciﬁctherapy, nor isthere any vaccineagainst

enteroviruses other than the polioviruses. Only symptomatic treatment is

available.

LABORATORY DIAGNOSIS

Isolation of virus from stools, rectal swabs, nasopharynx samples, CSF,

vesicular ﬂuid and eye secretions has until recently been the most reliable

method for laboratorydiagnosis of an enterovirusinfection. Several types of

cell culturesmay be usedfor isolation. Appearanceof cytopathic effect(CPE)

is observed after a few days, and neutralization tests are used for virus

identiﬁcation. Inoculationof coxsackie viruses intonewborn mice willlead to

disease anddeath.

During the last years molecularvirological methods such as PCR for the

detection of enterovirus nucleicacid (RNA or cDNA) have beendeveloped,

and nested PCR is considered to be more sensitive than virus isolation,

particularly sincesome enterovirus strainsdo notgrow or failto show CPEin

cell culture.

Samples shouldbe taken inthe early phaseof the diseasesince patients will

usually excretevirus inthe faecesfor about1 week(several weeks forchildren).

Presence ofvirus is a strongindication of acausal relationship to disease.As

virus sheddingmay beintermittent duringthe later phasesof illness,a negative

result doesnot exclude recent infection.

Antibody investigations.A test for speciﬁcIgM is usedin some laboratories

and isconsidered to be the methodof choice for coxsackievirusB infections.

The CFTis easy to perform,but because ofthe occurrence of cross-reactions

the CFTis of limited valuefor enterovirus diagnosis.

MIGHT ASWELL TAKE SOMETHINGENJOYABLE

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

9. RHINOVIRUSES AND

CORONAVIRUSES

Lat. rhinus¼ nose;Ger. Erka

ltung; Fr.rhuˆme¼ common cold.

I. Ørstavik

Rhinoviruses arethe mostfrequent causeof common colds.All agegroups are

affected. Infections are endemic with higherfrequencies during autumn and

spring intemperate climates.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

The commoncold is spreadby close contactand by inhalationof virus-

containing droplets.The incubation period is2–4 days, and aperson is

probably infectious from 1 daypostinfection and as long as there are

clinical symptoms.

SYMPTOMS AND SIGNS

Systemic: None orLow-Grade Fever, Headache

Local: Coryza, Sneezing, Sore Throat,Cough,

Hoarseness

In uncomplicatedcases theillness usually lastsfor 1week, with maximal

symptoms ondays 2 and 3.

COMPLICATIONS

Secondary bacterial infections may occur (sinusitis, otitis media).

Rhinovirus infections may precipitate acute asthma in predisposed

children, andmay aggravate chronic bronchitisin adults.

THERAPY AND PROPHYLAXIS

No speciﬁctherapy or prophylaxis isavailable.

LABORATORY DIAGNOSIS

During acute illnessthe virus can beisolated from the nose,the throat

and sputum.Special cellculture techniquesare needed forvirus isolation

and these are performed in very few virus laboratories. Serological

diagnosis isnot routinely used either,because of themany serotypes.

Figure 9.1 RHINOVIRUS (THECOMMON COLD)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

After an incubation period of2–4 days, the illness starts with symptoms of

nasal congestion/blockage and irritation, sneezingand a sore throat. Excess

nasal secretion follows whichis serous at ﬁrst and laterbecomes purulent if

secondary bacterial infection ensues. Cough is a frequent symptom, as is

headache during theﬁrst days of illness.Fever occurs seldom, andif so, it is

moderate. Rhinovirus infectioncauses the same symptoms inall age groups.

The infection is limited to the respiratory tract. It has been suggested that

rhinoviruses maycause a moreserious infection of thelower respiratory tract

in small children. Rhinovirus infection has also been shown to precipitate

attacks of asthma in children and aggravate chronic bronchitis in adults.

Asymptomatic infections are reported tooccur in about 25% of individuals

infected withrhinovirus.

Differential diagnosis. Symptoms of common cold, particularly in children,

may be due to oth ervirus infections, e.g. inﬂuenzavirus, parainﬂuenzavirus,

adenovirus, RSVand coronaviruses. Coronaviruses arenow considered to be

second to rhinoviruses as a cause of common cold, but the symptoms are

usually milder in coronavirus infections. Inﬂuenzavirus infections occur in

epidemics, andgeneral symptomssuch asfever andmalaise are moresevere. In

parainﬂuenza and adenovirus infections pharyngitis is more pronounced.

During epidemicsof RSVsome of thepatients, children aswell asadults, may

have thesame symptomsas in rhinovirusinfections. Pharyngitis andtonsillitis

will dominate infections with Streptococcus pyogenes.However, it is usually

not possible to determine the aetiology on the basisof the clinical ﬁndings

alone inupper respiratory infections.

CLINICAL COURSE

As arule, the illness willlast for 1 week,but 25% of thepatients will need 2

weeks torecover completely.The illnesstends to lastlonger insmokers thanin

non-smokers.

COMPLICATIONS

Bacterial sinusitis and otitis media are the most common complications.

Occasionally abacterial bronchopneumonia is seen.

THE VIRUS

Rhinovirus and Enterovirusare two genera inthe family Picornaviridae. They

are small(28–32 nm) single-strandedRNA viruses (Figure9.2).

Rhinovirus nowcomprises morethan 100

different serotypes, and newtypes are still

being identiﬁed. As with other picorna-

viruses thevirion capsidconsists of anaked

icosahedron of60 capsomers,each madeup

of four proteins. Depressions in the virus

capsid representthe siteson thevirus where

the cellular receptors bind. These depres-

sions (‘sockets’) are the targets for

experimental studies of synthetic anti-

rhinoviral agents. A ﬁfth protein is

associated with the single-stranded RNA.

Dueto the lackof alipid envelope,the virus

is resistant to inactivation by organic

solvents. Rhinoviruses aremore acid-labile

than enteroviruses.

EPIDEMIOLOGY

The rhinoviruses probablycause about half ofall cases of commoncold and

are considered to be one of the most frequentcauses of infections in man.

Studies inthe USAhave revealedan infectionrate of atleast 0.6per individual

per year. The rate is highest among infants and decreases with age.

Schoolchildren are considered to be important transmitters of rhinovirus

infections.Par entswith childrenin kindergartenor inprimary schoolmay have

more common cold episodes than single adults. Rhinovirus infections are

endemic, but occur most frequentlyduring autumn and spring in temperate

climates. Several serotypes can circulate simultaneously in the same

population, and it is possible that new serotypes emerge over the years.

There is noevidence that some serotypes causemore serious illness or occur

more frequentlythan others.

THERAPY AND PROPHYLAXIS

Speciﬁc chemotherapyis not available, andtreatment with immunoglobulinis

without effect. Experiments in volunteers have found a-andb-interferon

given intranasally to be effectivein preventing rhinovirus infection, whereas

studies using g-interferon have been unsuccessful. The suggestion thatlarge

quantities ofvitamin C (ascorbicacid) takenpro phylacticallyor duringillness

inﬂuences the course of the disease, has not been proven. Symptomatic

treatment includes mild analgesics and nasal drops. Prophylactic use of

antibiotics against bacterialsuperinfections is not recommended inotherwise

healthy individuals.

No vaccine is available. Thehigh and uncertain number of serotypes and

their relative importance and distribution during various outbreaks are

Figure 9.2 RHINOVIRUS

(Electron micrograph courtesy

of E.Kjeldsberg)

obstacles tovaccine development.In addition toinhalation ofdroplets, spread

of infectionby contactis consideredto playa signiﬁcant role.Measures should

be takento avoid infection fromvirus-contaminated hands. Personssuffering

from asthma and from chronic bronchitis should avoid close contact with

common coldpatients.

LABORATORY DIAGNOSIS

Cultivation ofrhinoviruses requiresspecial cellcultur eswhich areincubated at

338C (the temperature inthe nasal mucosa). Also, since many serotypes are

difﬁcult to cultivate,rhinovirus isolation is performedonly by very fewvirus

laboratories. Serological diagnosis is complicated by the large number of

serotypes andis therefore not routinelyperformed.

CORONAVIRUS

Coronaviruses are thesecond most frequent cause of thecommon cold (15–

20%). They aresingle-stranded RNA viruses belonging to theCoronaviridae

family. Thevirions varyin diameterfrom 80to 160nm. Theyhave club-shaped

spikes on the surface which give a crown (corona)-like picture by electron

microscopy (Figure 9.3).At least four different proteins areknown , and the

S (spike)-protein induces virus-neutralizing antibodies contributing to

immunity. The coronaviruses are divided into three serological groups, the

human coronaviruses havebeen allocated to twoof these serological groups,

and the two human prototypes are OC43and 229E. The coronaviruses are

believed to spread asthe rhinoviruses, and the incubation period isabout 2

days. The symptoms are similar to those following rhinovirus infections,

lasting for about1 week. As manyas 50% of coronavirus infectionsmay be

asymptomatic. Serological studiessuggest that the infection occursin all age

groups. Reinfection viruses have been

observed, suggest ing that protective

immunity is not long-lasting. Corona-

virus infectionsoccur most frequentlyin

late winter/early spring. Coronavirus

may be isolated from the nose and

throat during the acutephase of illness

if organcultures of human fetaltrachea

are used. Only a small number of

coronavirus strainshave been identiﬁed,

and most knowledge about this virus

infection has been obtained by sero-

logical studies on paired sera from

patients. Veryfew laboratories diagnose

coronavirus infections as part of their

routine work.

Figure 9.3 CORONAVIRUS.

Bar, 100nm (Electronmicrograph

courtesy ofE. Kjeldsberg)

A REALKNOCK-OUT

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

10. INFLUENZAVIRUSES

Inﬂuenza; inﬂuencedby cosmic events (medievalItaly). Ger. Grippe;

Fr. grippe.

L. R.Haaheim

Inﬂuenzavirus causes illness in all age groups. During epidemics a large

number ofindividuals may fall illwithin a spanof a few weeks.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Virus is transmittedby aerosols, mean incubation timeis 2 days (1–4).

The patientis contagious during theﬁrst 3–5 daysof illness.

SYMPTOMS AND SIGNS

Systemic: Sudden Fever(38–408C), Myalgia, Headache

Local: Coryza, Dry Cough, SoreThroat, Hoarseness

Systemic symptoms dominateinitially with fever for theﬁrst 3–4 days.

Full recoverywithin 7–10 days. Occasionallylong convalesence.

COMPLICATIONS

Secondary bacterial pneumonia.More rarely primary viralpneumonia,

myocarditis, encephalitis.

THERAPY AND PROPHYLAXIS

No speciﬁc treatment. Amantadine chemoprophylaxis. Vaccination is

recommended forhigh-risk groups and keypersonnel within the health

services.

LABORATORY DIAGNOSIS

Virus can beisol atedfrom/demonstrated in nasopharyngeal specimens

taken in theacute phase of illness (days1–3). An antibody rise canbe

demonstrated inpaired sera by HIor CFT.

Figure 10.1 INFLUENZAVIRUS (INFLUENZA)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

Virus is transmitted by aerosols. The mean incubation time is2 days (1–4).

Prodromal symptoms are uncommon. A sudden onset ismost typical, with

chills andrising feverfollowed by myalgia(usually back painin adults).These

initial systemic manifestationsmay later be followed bysigns of pharyngitis/

laryngitis/tracheobronchitis. In conjunction with dry cough the patient may

complain of substernal pain. Other symptoms may be coryza, ﬂushed face,

epistaxis, photophobia,anorexia or vertigo. Croupamong small children isa

relatively commonfeature (see also Chapter11).

Differential diagnosis.A range ofacute respiratorydiseases are oftenmistaken

for ‘inﬂuenza’.Only laboratory tests canestablish the viral aetiology.

CLINICAL COURSE

The fever, after having peaked atabout 38–408C within 1–3 days, may fall

abruptly, butusually thereis agradual defervescencein the courseof 2–4days.

Occasionally a secondperiod of fever occurs. Whenafebrile the patient may

have aproductive cough andsuffer from fatigue.Respiratory tract symptoms

usually dominate the later phases of illn ess. Damage to the mucociliary

epithelium inthe airwaysmay take weeksto repair.Otherwise healthypatients

usually recovercompletely within 7–10 days.

COMPLICATIONS

The most common complication is secondary bacterial pneumoniawhich is

especiallyseriou samong theelderly andthose withchronic diseaseof theheart,

lungs and bronchi. The excess mortality associated with some inﬂuenza

epidemics is a serious community health problem. A biphasic fever may

indicate bacterial superinfection, and the bacterial pneumonia has a

particularly rapid course.Primary viral pneumonia is a rarerevent and may

be recognizedby a prolongedprimary fever, dyspnoea,hypoxia and cyanosis.

Encephalitis/encephalopathy isan extremely rarecomplication. Postinfectious

Reye’s syndrome has sometimes been seen in connection with inﬂuenza,

especially that due to inﬂuenza B virus. Myocarditis and transient cardiac

arrhythmia haveoccasionally been observed.

THE VIRUS

Inﬂuenzavirus is an enveloped single-stranded RNA virus belonging to the

family Orthomyxoviridae (Figure 10.2). Three types of inﬂuenzavir us are

known, namely types A, B (genus Inﬂuenzavirus A, B) and C (genus

Inﬂuenzavirus C). TypesB and C are believedto have man as theonly host,

whereas typeA virusis found ina widerange ofspecies, e.g. swine,horses and

birds. Two different types of spikes, the haemagg lutinin (H) and the

neuraminidase (N)protrude fromthe viral envelope.The formeris responsible

for attachment of virus to cellular receptors, and anti-H antibodies protect

against infection.The neuraminidase is believedto play arole in virusrelease

from infected cells. The neuraminidase splits off neuraminic acid from the

cellular virus receptor. Only rarely will anti-N antibodies neutralize viral

infectivity. For inﬂuenzaA the internal proteinsare the matrix antigen (M1)

surrounding thenucleocapsid and closelyattached to theviral membrane, the

nucleoprotein (NP) associated with the segmented viral genome and the

polymerases PA,PB1 and PB2.The division

intotypes is basedon theantigenic properties

of theM1 and NPproteins. Another protein

(M2), codedfor bythe same genesegment as

M1, is present in small quantities in the

infectious virion and functions as a proton

channel. Both surface antigens show a

marked tendency for antigenic variation

(‘drift’). This is the main reason for the

frequent recurrence of epidemics. Based on

genetic and antigenic characteristics of

inﬂuenza A surface antigens they can be

divided into subtypes,of which there are15

for the haemagglutinin and 9 for the

neuraminidase. The segmentedviral genome

allows for formation of viral reassortants

(‘recombinants’) between differentstrains or

subtypes of virus.A doubly-infected host can thusgive rise to a ‘new’virus.

Such a profound change in antigenic make-up (‘shift’) is probably the

mechanism forthe occurrence of newpandemic A strains.Exchange of genes

between animaland human inﬂuenzaA subtypes mayplay an important part

in this phenomenon.Also gene combinations for virulencecan be reassorted

between viruses.In Hong Kong in1997 a very virulentavian inﬂuenza strain

(A/H5N1) surprisingly infected people directly without any animal inter-

mediary. No interhuman spread was observed. This zoonosis caused

considerable internationalconcern.

EPIDEMIOLOGY

New inﬂuenzastrains with changesin oneor both surfaceantigens are ableto

evade the herd immunity built upto previous strains. In 1957 the A/H2N2

subtype (‘Asian ﬂu’) replaced the A/H1N1 virus, resulting in a pandemic

situation. In 1968 a new shift occurred giving rise to the A/H3N2 subtype

Figure 10.2 INFLUENZA-

VIRUS. Bar, 50nm (Electron

micrograph courtesy of G.

Haukenes)

(‘Hong Kong inﬂuenza’). Since 1968 variants of the H3N2 virus have

continued tocirculate. Unexpectedly,in 1977 theA/H1N1 subtypereappeared

in China after being out of circulation since 1956. Initially this virus

predominately infected young individuals and spread all over the world in

the course ofapproximately 1 year. Variants of thisvirus have continued to

circulate. Thus,presently we have strainsof two inﬂuenzaA subtypes (H3N2

and H1N1) co-circulating. Inﬂuenza A pandemics occur at long and

unpredictable intervals (decades), whereas larger epidemics of inﬂuenza A

appear onaverage every 2–4years. Inﬂuenza Bvirus is lessprone to antigenic

drift and gives larger outbreaks somewhat less frequently. Inthe temperate

zones epidemics usually occur duringthe winter season, but sporadic cases/

outbreaks may takeplace throughout the year. Factorsdetermini ngwhether

epidemics takeplace or not arenot well understood.The antigenic properties

of thevirus together withfactors related to transmissibilityand virulence and

the extent ofherd immunity in thepopulati onall play a role.Age-related as

well asregional andlocal differences inseverity anddegree of epidemicimpact

are frequently observed. Thus, prediction of epidemics and their special

parameters is extremely difﬁcult andin most cases not possible. The World

Health Organization (WHO ) has set up a global surveillance system for

inﬂuenza. About 110 national institutes in more than 80 countries form a

cooperative international network whosemain task is to monitor epidemics,

isolate strains anddisseminate information to allmembers on a weekly basis

throughout the winter season. WHO recommendations for the antigenic

composition ofthe vaccines arebased onan international scientiﬁcconsensus.

THERAPY AND PROPHYLAXIS

Treatment is mostly symptomatic. Ext ensive use of salicylates should be

discouraged due to its possible precipitating effect on the development of

Reye’s syndrome. Immunoglobulin has neither therapeutic nor prophylactic

effect. Amantadine and its derivatives have a proven prophylactic and

therapeutic effect on inﬂuenza A (see p. 31). New promising drugs against

both inﬂuenzaA andB, targeted againstthe virionneuraminidase activity, are

under clinicaltrials. Inﬂuenza vaccinewill, provided the antigenicformulation

does not differ signiﬁcantly from the epidemic strain, confer protection in

about 75%of recipients. The inactivatedvaccines used throughout theworld

are puriﬁedegg-grown viruskilled byformalin orby b-propriolactone.The use

of live attenuated vaccine is limited. Preparations containingdetergent split

virus or isolatedsurface subunits (H and N)are mostly used. The twolatter

types ofvaccine areclaimed togive fewer side-effectsthan wholevirus vaccine.

About 15–40%of thevaccinees willexperience slightredness andinduration at

the injection site, and some show signs of mild inﬂuenzal disease of short

duration. Apartfrom theassociation ofpolyradiculitis withthe swineinﬂuenza

vaccine programme in the USA in 1976, there are no known systemic

complications to inﬂuenza inoculation. Persons for whom clinical inﬂuenza

would lead to further deterioration of their underlying condition are

recommended as target groups for routinevaccination. Generally, these are

the elderly, those withchronic illnesses in the heart, lungs andairways, and

those withmetabolic disorders or immunedeﬁciencies. As a routinemeasure,

inﬂuenza vaccination shouldbe carried out beforethe usual time of onsetof

epidemics. In temperate climates this means vaccination duringthe autumn

months. Protective levels of anti-inﬂuenza antibody will ensue 1–3 weeks

postvaccination. Immunityto inﬂuenza, whether throughnatural infection or

vaccination, will lastfor about a yearas the ever-changing viruswill outdate

acquired immunity.

LABORATORY DIAGNOSIS

Inﬂuenzavirus can be isolated in cell cultures or in fertile hens’ eggs from

nasopharyngeal samplestaken inthe acute phaseof illness.The physician may

get a laboratory answer within a week. More rapid diagnostic methods,

demonstrating (e.g. byIF) virus or viral materialin the sample within afew

hours, are nowavailable in some laboratories. More specializedlaboratories

offer subtype identiﬁcationof inﬂuenza A virus. In pairedsera, taken in the

acute phase and 10–14 days after onset, a signiﬁcant CF antibody rise is

indicative of recentinfection with either A orB virus. HI tests may insome

cases indicatewhich inﬂuenzaA subtypeis theaetiological agent.How ever,HI

tests may in some instances give misleading or inconclusive resul ts due to

‘original antigenic sin’.This phenomenon is a poorlyunderstood anamnestic

HI antibody recall of childhood inﬂuenza memory triggered by current

heterotypic strains.

HOME CURED

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

11. PARAINFLUENZAVIRUSES

The namerelates to the afﬁnityof the virusfor the respiratory

tract givingmild inﬂuenza-like diseases.

A. B.Dalen

Parainﬂuenzaviruses (four serotypes) are important pa thogens of the

respiratory tract in infants, children and young adults. They are the major

cause ofcroup, and also causebronchiolitis and pneumonia.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Virus is transmitted by close contact or inhalation of droplets. The

incubation periodis 2–4 days (children)and 3–6 days(adults).

SYMPTOMS AND SIGNS

Systemic: Slight Feverand Malaise

Local: Cough, Hoarseness, Coryza, Croup

Most childrenrecover within 3–6 days.

COMPLICATIONS

Rarely seen.Atelectasis may develop followingpneumonia.

THERAPY AND PROPHYLAXIS

No speciﬁc antiviraltreatment. Symptomatic treatment aims to relieve

respiratory distress.The use of corticosteroidsis controversial.

LABORATORY DIAGNOSIS

Viruses maybe isolatedin cell cultures.PCR detection maybe used. IF

is used to demonstrate viral antigen in nasopharyngeal aspirates.

Serodiagnosis isof little practical value.

Figure 11.1 PARAINFLUENZAVIRUS (RESPIRATORYINFECTION)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

The incubationperiod is2–4 days. Aftersigns of rhinitisand pharyngitis fora

few days,the patient may becomehoarse and have inspiratorystridor. There

may be amild to moderate fever. Involvementof the lower respiratory tract

(bronchitis andbronchopneumonia) is seenin 30% ofprimary infections with

type 3 virus. Severe croupis seen in 2–3% of primary infections with virus

types1 and 2.The parainﬂuenzavirusesare secondonly torespiratory syncytial

virus asthe causeof seriousrespiratory tract infectionsin infantsand children.

Parainﬂuenzavirus 1and 2 mostoften give infections affectingthe larynx and

the uppertrachea whichmay resultin croup,while type3 hasa predilection for

the lower respiratorytract giving bronchitis, bronchiolitis and bronchopneu-

monia.Type 4virus isless virulent,being associatedwith mildupperrespiratory

tract illnessin children andadults. Due tothe presence ofprotective maternal

antibodies, serious illnessdue to parainﬂuenzavirus 1 and 2infections is not

seenbefore theage of4 months.For type3 virusseriousilln essisseen inthe ﬁrst

months oflife inspite of thepresence of maternalneutralizing antibodies.The

incidence of severe infections increases rapidly after the age of 4 months,

peaking betweenthe ageof 3and 5years. Theincidence islower whenthe child

reaches school age, and clinical disease from parainﬂuenzavirus 1, 2 and 3

infections is unusual in adult life. Reinfections with the same type ofvirus

occur frequently,but with milder clinicalmanifestations.

Differential diagnosis. Croup is occasionally caused by RSV and inﬂuenza-

viruses. In bronchitis, bronchiolitis andbronchopneumonia in infancy other

viruses, notablyRSV, mustbe considered.Chlamydia trachomatis causeslower

respiratory tractinfections in early infancy,while Chlamydia pneumoniae and

Mycoplasma pneumoniae are more commonly found in older children and

young adults. The most important differential diagnosis to viral croup is

bacterial croupor epiglottitiscaused by Haemophilusinﬂuenzae type B.This is

a life-threatening condition which usually starts without prodromal rhinitis

and hoarseness. The patient has dysphagia anda higher fever than in viral

croup anda toxicappearance. Theepiglottis appearsenlarg edand inﬂamedon

inspection. Respiratorydistress doesnot tend tobe diminishedby bringing the

patient into an upright position. Diphtheritic croupis now a rare illness in

many countries.The condition is characterizedby marked swelling oftonsils,

the presenceof membranes, prostration andhigh fever.

CLINICAL COURSE

Fever usually lasts for 2–3 days. Most children recover uneventfully from

croup after24 to 48hours. When bronchiolitis andpneumonia develop, fever

and coughpersist for some time.

COMPLICATIONS

Atelectasis may developfollowing lower respiratory tractinfections .Compli-

cations areotherwise very rare.

THE VIRUS

The parainﬂuenzaviruses belong to the genus Paramyxovirus, family

Paramyxoviridae (Figure 11.2). The viral genome, a single-stranded RNA

of negative polarity and about 15,500 nucleotides in length, is surrounded

by core proteins and an outer lipid

membrane, bearing glycoprotein spikes.

These surface glycoproteins include a

bifunctional protein, the haemagglu-

tinin–neuraminidase, and the fusion

protein. The haemagglutinin is respon-

sible for attaching the virusto host-cell

receptors. The neuraminidase functions

late in theinfection cycle, releasing new

virions from infected cells. The fusion

protein mediatespenetration of the viral

core throughthe cytoplasmic membrane

of the host cell. This protein also

mediates the characteristic fusion of

cells seen in infected tissue. The fusion

protein isrendered biologically activeby

a cellular protease, a process which is

essential for infectivity. Antibodies

against the haemagglutinin–neuraminidase and the fusion proteins have

neutralizing properties. The parainﬂuenzavirusesshare antigens with mumps

virus and parainﬂuenzaviruses of animal origin. The four serotypes of

parainﬂuenzavirus differ in antigenic composition and to some extent in

cytopathogenicity andclinical manifestations.

EPIDEMIOLOGY

Parainﬂuenzaviruses 1 to 4 are ubiquitous and infect the respiratory tract.

There issome seasonal variationwith fewer casesduring the summermonths.

The virusesare readily spread,which gives riseto high infectionrates in early

life. Type3 virus ismore easily spreadthan types 1,2 and4, and occursmore

commonly during infancy andearly childhood. Infections with type 1and 2

virus occur somewhat later, but the majority of children have experi enced

infections withthese viruses by theage of 5.Infect ionsgive rise toboth local

nasal secretory IgA andserum-neutralizing antibodies. The IgA from adults

neutralizes viral infectivity, while locally produced IgA from young infants

Figure 11.2 PARAINFLUENZA-

VIRUS: RUPTURED VIRION

WITH HELICAL NUCLEOCAP-

SIDS.Bar, 100nm (Electronmicro-

graph courtesyof G. Haukenes)

lacks orhas littleneutralizing capacity. Serum-neutralizingantibodies areonly

partially protective, and reinfections probably occurrepeatedly. The clinical

manifestations aregenerally less severeduring reinfections. Afterthe age of7,

parainﬂuenzavirus infectionsare usually subclinical.

THERAPY AND PROPHYLAXIS

Inactivated vaccines have been shown not to prevent parainﬂuenzavirus

infection or disease. Speciﬁc antiviral treatment is not available. The

importance of interferon in recovery from parainﬂuenzavirus disease is not

known. Symptomatic treatment of croup includes keepingthe patient in an

upright position in a humidiﬁed and cooled atmosphere, and correction of

hydration. Regimens includingthe use of nebulized racemic epinephrineand

systemic corticosteroidsare controversial.Intubation may beindicated onrare

occasions withsevere respiratory distress.

LABORATORY DIAGNOSIS

Routine laboratorydiagnostics are usuallylimited toparainﬂuenzaviruses 1, 2

and 3. The viruses grow well in tissue culture. The lability of the viruses,

however, makes inactivation of the virus during transportation a problem.

PCR detectionavoids thisproblem. The directdemonstration ofvirus-infected

cells from nasopharyngeal aspirates by immunoﬂuorescence is a very good

practical alternative. A conclusive answer can be given withina few hours.

Serodiagnosis by HI,CF or NT requires paired serataken 1–3 weeks apart.

This delayrenders serodiagnosis impractical ina clinical setting.

OF INFLATEDIMPORTANCE?

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

12. MUMPS VIRUS

Epidemic parotitis.Ger. Ziegenpeter;Fr.oreillon.

B. Bjorvatnand G. Haukenes

Inﬂammation ofthe salivaryglands maybe caused bybacterial, fungalor viral

infection, or by toxic–allergic reactions. Acute enlargement of the salivary

glands in children and youngadults is mostly due to infection with mumps

virus.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Infection istransmitted through inhalationof virus-containing aerosols.

The incubat ionperiod isusually 2–3weeks. Periodof communicabilityis

from afew days before, toabout 1 weekafter clinical onset.

SYMPTOMS AND SIGNS

Systemic: Fever

Local: Painful Swelling of SalivaryGlands

Others: See Complications

In uncomplicatedcases recovery is completewithin 1 week.

COMPLICATIONS

Most commoncomplications are meningitisand orchitis. Theprognosis

is usuallygood.

THERAPY AND PROPHYLAXIS

No therapeutic or prophylactic value of drugs or speciﬁc immuno-

globulin. Complications are treated according to sympt oms. Live

attenuated virus vaccines are available that provide more than 90%

protection.

LABORATORY DIAGNOSIS

Virus canbe isolated incell culture fromsaliva collected duringthe ﬁrst

week ofdisease, andin urine somewhatlonger. Duringthe ﬁrst 4–5days

of mumps meningitis, the virus may be found in spinal ﬂuid. Serum

antibodies aredetect able1–3 weeks after clinicalonset. The serological

diagnosis isbased on seroconversion orthe speciﬁc IgM byELISA.

Figure 12.1 MUMPS VIRUS(MUMPS)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

The incubation period is usually 2–3 weeks. Typically, thepatient develops

slight/moderate feversome days beforeswelling of thesalivary glands, mostly

the parotid glands. In about 80% of the cases there is abilateral swelling,

appearing within an interval of one or several days. A continuous swelling

involving thesalivary glands, the jawregion and lateralaspects of theneck is

not uncommon. Thepatient complains of oral dryness andpainful chewing,

and occasionallythere is trismus.Oedema and redness aroundthe opening of

the Stensen’s duct are frequently seen. Mumps that remains located

symptomatically to the salivary glands is considered uncomplicated and

recoveryis usually completewithin 1week orless. Asymptomaticinfections are

common (atleast 20–30%), particularly inearly childhood.

Differential diagnosis. Mononucleosis or bacterial infections of oropharynx,

sialoadenitis (anomaliesof the glandularduct, immune deﬁciency),other viral

infections of salivary glands (rare), allergic reactions, collagen disease and

lymphoma. The diagnosis is us ually made clinically, particularly during

epidemics. Incase of doubt, laboratoryconﬁrmation should be obtained.

CLINICAL COURSE

In uncomplicatedcases of mumps completerecovery is expectedin 1 week or

less.

COMPLICATIONS

Asymptomatic pleocytosis (45 leukocytes/mm

) of the cerebrospinal ﬂuid is

found in 50–60% of mumps cases. Symptomatic meningitis or meningo-

encephalitis occursin 1–3%of cases,three times morefrequently inmales than

in females. Clinically,the picture is dominatedby headache, rigidity ofneck,

nausea, emesis and fever. Examination of spinal ﬂuid often reveals a

considerable mononuclear pleocytosis. There is poor correlation between

severity of clinical disease and number of cells in the cerebrospinal ﬂuid.

Meningitis occursat thetime of, or4–7 days followingglandular involvement,

but mayoccur inthe absenceof salivarygland swelling. Theprognosis isgood.

Young children tend to recover in a few days, whereas teenagers and

particularly adultsoccasionally require weeks(months) forcomplete recovery.

Mumps encephalitis without signsof meningitis is reported in 0.02–0.3% of

cases. Permanentneurological sequelaesuch as unilateralhearing lossor facial

nerve palsymay occur in suchcases.

Orchitis complicates the course inapproximately 20–30% of postpubertal

males. This condition is characterized by fever, intense pain and often

considerable swelling of the testicle, frequently occurring when the salivary

gland enlargement has subsided. Orchitisis usually unilateral, but the other

testicle mayoccasionally (20%) be affectedwithin a few days.Prostatitis and

epididymitis may also occur. The symptoms of mumps orchitis normally

disappear within1 week.Although parenchymatousnecrosis may lead to some

testicular atrophy,permanent infertility is veryrare, even in casesof bilateral

involvement. Temporary reductionin fertility is not uncommon, however.A

history ofmumps orchitis appears tobe a riskfactor for testicular cancer.

Oophoritis occursin about5% offemale mumpspatients, butdoes notcause

infertility.

Pancreatitis, diagnosedin about 7% ofcases, heals uneventfully.Note that

high levels of amylase mayresult from swelling of the salivary glands only.

Occasionally other glands (thyroid, lacrimal, mammary and thymus) are

involved. Onrare occasions involvement ofliver, spleen, joints, myocardium,

retina andconjunctiva has been reported.

THE VIRUS

Mumps virus(Figure 12.2) belongs tothe genus Paramyxovirus ofthe family

Paramyxoviridae. The mumps virus particle is pleomorphic, 150–200 nm in

diameter. The envelope and the underlying matrix surround a helical

nucleocapsid containing a single molecule of negative-sense single-stranded

RNA. Theenvelope contains three glycosylatedprotei ns,H (haemagglutinin,

attachment protein), F (fusion protein,haemolysin) and N (neuraminidase).

The M (matrix) protein lies beneath the envelope. Associated with the

nucleocapsid areP (phosphoprotein) Nand NP (RNA-bindingprotein) and a

large (L) protein(RNA polymerase). Virus enters thecell by fusion with the

cell membrane.The viral RNA istranscribed to apositive strand from which

proteins are translated and new genomic

RNA is made. During this transcription

two additional proteins are coded by

the P gene, one by ribosomal frameshift

(C protein)and one (Vprotein) by a newly

recognized strategy including occasional

insertion of additional nucleotideresul ting

in frameshifting (RNA editing). Nucleo-

capsids aremade in thecytoplasm, and the

virus matures by budding from the cell

membrane. Thevirus is unstableand easily

destroyed by ether, heatin gat 568C for 20

minutes, ultraviolet irradiation and treat-

ment withmost disinfectants.

Figure 16.2 MUMPS VIRUS.

Bar, 100nm (Electron

micrograph courtesyof

G. Haukenes)

EPIDEMIOLOGY

Mumps virus is mainly transmitted by airborne droplets when contagious

persons arein contactwith susceptibleindividuals. Althoughmumps virusmay

be foun din thesaliva from6–7 daysbefore andup to8 days followingonset of

disease, transmissionis most efﬁcient aroundthe time of onset.Transmission

alsooccurs in casesof subclinicalinfection. Thesusceptibility isconsiderable in

non-immune populations, asreﬂected by annual incidence rates between 0.1

and 1%.Peak incidences are foundin the 5–7year agegroup. Small children,

and inparticular infants, rarelycontract thedisease, or thedisease more often

runs an asymptomatic course. In tropical climates mumps is endemic

throughout the year. In temperate climates the disease ismost prevalent in

the winterand spring, tendingto cause larger epidemicsat 3–5 yearintervals.

With increasingvaccination coverage,mumps has largelydisappeared inmany

industrialized countries.

THERAPY AND PROPHYLAXIS

There is no speciﬁc chemotherapy available,and high-titred immunoglobulin

has no proven therapeutic effect. In cases of meningitis the patient should

remain inbed and analgesics,antipyretics and antiemeticsshould be provided

as needed. Similar symptomatictreatment is instituted for orchitis, which in

addition may require a mechanical support, local cooling (ice bags) and

possibly systemiccorticosteroids. Prophylactic useof speciﬁc immunoglobulin

has nodocumented effect. Safe andeffective live attenuated vaccinebased on

virus fromchick embryoﬁbroblasts provides morethan 90% protectionfor at

least 10years followingone single injection.Mild side-effects(low-grade fever,

local tenderness) are occasionally seen.On very rare occasions such vaccine

strains maycause amild meningitis.Mumps vaccine,either asa monovalent or

a combinedtrivalent vaccinewith measlesand rubella (MMR),may beoffered

at the age of 15–24 months, followed by a second injection at prepuberty.

Pregnancy, ongoing infectious diseases (except mildinfec tions)and immune

deﬁciency areall contraindications for suchlive vaccines.

LABORATORY DIAGNOSIS

During the ﬁrst week of disease, virus can be isolated from saliva or oral

washings. Successfulvirus isolation may bemade from urine foranother 1–2

weeks. Virus may also berecovered from the cerebrospinal ﬂuid during the

acute stage ofmeningoencephalitis. Mumps virus replicatesin different types

of cellcultures, but monkey kidneycell lines arepreferred. The virus-induced

cytopathic effect manifestsas giant cells anddegenerative changes leading to

cell death. Virus-infected cellsadsorb erythrocytes, and this haemadsorption

(Had) isinhibited by speciﬁc mumpsantibodies (HadI). Virus isidentiﬁed by

neutralization, immunoﬂuorescence(cytoplasmic and membrane)or by HadI.

For serological diagnosis,seroconversion or speciﬁc IgM isusually looked

for. Signiﬁcant rises in titre are looked for by ELISA. Antibodies can be

detected 1–3 weeks after clinical onset. Detection of speciﬁc IgM indicates

onging orrecent (within weeks/months) infectionwith mumps virus. Possible

cross-reaction with other parainﬂuenzaviruses should be kept in mind in

evaluation ofimmunity status.

RAPID DIAGNOSISLEADS TO CORRECTMANAGEMENT

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

13. RESPIRATORY SYNCYTIAL

VIRUS (RSV)

The namereﬂects the ability ofthe virus toinduce

syncytia (giantcells) in tissue cultures.

G. A

nestad

RSV is the most important pa thogen encountered in lower respiratory

tract infections (bronchiolitis and pneumonia)in infants and small children.

Among older children and adultsreinfections are common. Clinically, these

reinfections areusually manifestedas upperrespiratory tractinfection (URTI).

Epidemics of RSV occur regularly during the colder months in temperate

climates andduring the rainy seasonin tropical areas.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Infection is transmitted by contact with infectious material and by

aerosol. Theincubation periodis 3–6days. Thepatient is contagious1–2

weeks afteronset of symptoms.

SYMPTOMS AND SIGNS

Systemic: Moderate Fever,Hypoxaemia, Fatigue

Local: Coryza, Cough, Respiratory Distress

Other: See Complications

The periodof critical illnesslasts a fewdays. Infants andsmall children

often havea convalescent periodof someweeks with coughand fatigue.

COMPLICATIONS

Bacterial superinfections are uncommon. Small children who develop

bronchiolitis are probably predisposed todevelop asthma in later life.

Viral otitismedia is seen in20% of patients.

THERAPY AND PROPHYLAXIS

Ribavirin administered as an aerosol may have a beneﬁcial effect.

Otherwise onlysymptomatic treatment isavailable. In infantsand small

children RSV pneumo nia and bronchiolitis may be life-threatening,

requiring immediate hospitalization. RSV immunoglobulin may have

some prophylacticeffect. No vaccine isavailable.

LABORATORY DIAGNOSIS

Antigen detection (IF, ELISA) in exfoliated nasopharyngeal cells is

widely used. Serologicalexaminations for signiﬁcant titrerise are often

unrewarding, particularlyin infants.

Figure 13.1 RESPIRATORY SYNCYTIALVIRUS (BRONCHIOLITIS)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

The period fromexposure to onset ofsymptoms is usually 3–6days. Among

both small children and adults the ﬁrst symptoms are those of URTI with

cough andrhinorrhoea. RSVbronchiolitis developsonly insmall children, and

the most severe cases are usually children under 12 months of age. Lower

respiratory tract involvement usually occurs within the ﬁrstweek of illness.

Clinically, wheezing and increased respiratory rate with intercostal and

subcostal retractions are seen. In severe cases cyanosis, listlessness and

apnoea may occur. RSV bronchiolitis and pneumonia are often difﬁcult to

differentiate, andmany infantsappear tohave both.Chest radiographsmay be

normal, but oftenshow a combination of airtrapping (hyperexpansion) and

bronchial thickening or interstitial pneumonia. Fever is seen in the URTI

period and is moderate (38–408C). Preterm infants and children with

underlying diseases, inparticular those with cardiopulmonaryand congenital

heart disease, are at high risk fordevelopi ngsevere RSV infection. Among

school childrenand adults,RSV infectionmanifests asa common cold. Elderly

persons, and in particular those in institutions, may develop pneumonia,

sometimes withfatal outcome.

Differential diagnosis ofRSV infection in infants andsmall children includes

other causes oflower respiratory tract illness inthis age group, in particular

other respiratoryvirus infections (parainﬂuenzaviruses,inﬂu enzavirus,adeno-

virus). In infantsinfection with Chlamydia trachomatis may causeinterstitial

pneumonia with cough and in some instances wheezing. Contrary to the

abrupt onset of RSV bronchiolitis, this latter illness tends to be subacute,

and inapproximately 50% ofthe cases theillness is heralded bya chlamydial

conjunctivitis. In immunodeﬁcient children, Pneumocystis carinii infection

must be considered. In someinfants with RSV infection, the cough may be

so severe andparoxysmal that the illnessmay mimic the pertussissyndrom e.

The epidemic occurrence of RSV infection may be a guide to correct

diagnosis.

CLINICAL COURSE

In hospitalizedchildren thecritical period usuallylasts for3–6 days. However,

hypoxaemia maylast forsome weeks. Themechanisms involvedin recoveryof

RSV infectionare not fullyunderstood. Contrary toother respiratory viruses,

RSV induces little or undetectable levels of interferon and improvement

usually coincideswith the development oflocal and humoral antibodies.

COMPLICATIONS

Secondary bacterial complications are rare. Therefore, indiscriminateuse of

antibiotics shouldbe discouraged. Approximately 20% ofchildren with RSV

bronchiolitis develop aviral otitis media. Evidence isnow accumulating that

small ch ildrenwho havehad RSVbronchiolitis duringtheir ﬁrstyear oflife are

predisposed todeveloping chronic respiratory disease,in particular asthma.

THE VIRUS

RSV (Figure 13.2) belongs to the genus Pneumovirus in the family

Paramyxoviridae,subfamilyPneumovirinae. Thelinear single-strandednegative-

strand RNA hasa length of about15 kb. Viralreplication takes place in the

cytoplasm of virus-infected cells and, like other members of the family

Paramyxoviridae, infectious virions are

released by budding through the cell

membrane. However, RSV has no

haemagglutinin or neuraminidase. The

envelope ispleomorphic andthe diameter

of thevirions ranges from120 to 200nm.

The viral genome codes for eight

structural and two non-structural

proteins. Based on analyses with mono-

clonalantibodies, RSV isdivided intotwo

antigenic subgroups (A and B). The

major differences between these

subgroups are attributed to the G

surface glycoprotein whichis responsible

for virusattachment tohost cells.There is

no knowndifference in clinicalproperties

between thetwo subgroups.

EPIDEMIOLOGY

RSV hasa worldwide distribution,and in temperateclim atesepidemics occur

almost yearl yduring thecolder months,whilst intropical areasRSV outbreaks

usually occurduring the rainyseason. Incountries in temperateclimates these

epidemics areusually very regular inboth size and timing.However, in some

sparselypopul atedareas (e.g.Scandinavia) epidemicstend toalternate between

greater and smaller outbreaks every second winter. RSV epidemics are

characterized bydistinct peaks usuallyreached 2–3months after theﬁrst RSV

cases arediagnosed. It hasbeen claimed insome reports that duringthe peak

of an RSVepidemic other outbreaks of respiratoryvirus (inﬂuenzavirus and

parainﬂuenzavirus) infections seem to be relatively rare. Typical for a

developing RSV epidemicis a sharp increase innumber of infants andsmall

Figure 13.2 RESPIRATORY

SYNCYTIAL VIRUS (Electron

micrograph courtesy of E.

Kjeldsberg)

children admitted to hospital with lower respiratory tract infection. The

incidence of RSVinfection severe enough torequire hospitalization has been

estimated torange from1 to3% of infantsborn eachyear. On theother hand,

serological surveys have revealed that approximately half the infants living

through asingle RSV epidemic become infectedand almost all childrenhave

been infected after living through two RSV epidemics. Thus, severe lower

respiratory tractinvolvement is rather theexception, even among infantsand

small children. Among older children and adults reinfections are fairly

common. These reinfections,which clinically contribute to thecommon cold

syndrome, probably represent the major RSV reservoir, whilst infants and

small children with severe lower respiratory tract involvement serve as the

visible parameterof RSV activity withinthe community.

THERAPY AND PROPHYLAXIS

Good supportivecare is ofgreat importance in thetreatment of patientswith

RSV-induced lower respiratory tract involvement. Since most hospitalized

children are hypoxaemic,humidi ﬁed oxygen is beneﬁcial. In severecases the

use ofa respiratormay benecessary. Manyinfants are moderatelydehydrated,

and intravenousﬂuid replacementshould be considered.Ribavirin given asan

aerosol hasbeen shownto have abeneﬁcial effect, bothon virusshedding and

on clinical illness. Trials with monthly intravenous infusion of RSV

immunoglobulin given to infants at high risk for severe RSV infection have

indicated a prophylactic effect. The use of vaccines, either inactivated or

attenuated formulations, has hitherto given disappointing results. As

nosocomial RSV infections are common, hospitalized infants and children

with suspected or proven RSV infection should be kept in isolation. Strict

general hygienic measures should be instigated as the hospital staff may

transmit RSV.

LABORATORY DIAGNOSIS

RSV antigen can be detected in exfoliated nasopharyngeal cells by

immunological methods (IF, ELISA). Samples are collected with a tube

connected tothe outlet ofa mucus collector.It is crucialto collect asufﬁcient

amount ofmaterial. If the transportationtime to the diagnosticlaboratory is

more than 3 to 5 hours, the samples should be processed at the clinical

department, eitherby separatingcells andmucus bya washingprocedure or by

making smearson slides of theuntreated aspirated material. Afterdrying the

preparation can be sentto thediagnostic laboratoryby ordinarymail. Withthe

ELISA technique, thetime factor is lessimportant. If the sampleis collected

during theﬁrst weekof illness, upto 90%of the actualRSV infectionsmay be

diagnosed with these methods. Several commercial kits for rapid bedside

diagnosis arenow available.The sensitivity andspeciﬁcity ofthese kits arenot

fully evaluated,particularly when usedat busy clinics.RSV infection canalso

be diagnosedby conventional virus isolationin tissue culture. However,viral

infectivity is readily lost during transportation, and virus cultivation and

identiﬁcation are cumbersome and time-consuming (1–3 weeks). Signiﬁcant

titre rise can be detected in paired seraby serological methods, but among

infants andsmall childrenserological testsfor RSVare rather insensitive.High

titres shouldbe interpreted with caution.

VACCINATION MAKESALL THE DIFFERENCE

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

14. MEASLES VIRUS

Lat. morbilli;Ger. Masern; Fr. rougeole.

N. A.Halsey

Measles is ahighly contagious, serious diseaseaffecting children, adolescents

and occasionallyadults.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Measles virus is transmitted from respiratory secretions by direct

contact, droplets or airborne transmission with inoculation onto

mucous membranes.The incubation period is10 (8–15) days.

SYMPTOMS AND SIGNS

Systemic: Fever andMalaise

Local: Rash, Cough, Coryza, Conjunctivitis,

Koplik’s Spots

Others: See Complications

In uncomplicatedcases the clinicaldisease improves by the third day of

rash andresolves by 7–10 daysafter onset ofrash.

COMPLICATIONS

The mostcommon complicationsaffect the respiratorytract andinclude

otitis media, laryngotracheobronchitis (croup), pneumonia and

secondary bacterial pneumonia. Encephalitis occurs in 1 per 1000

infected children. Subacutesclerosing panencephalitis (SSPE) is arare,

fatal complicationappearing after an intervalof 6–8 years.

THERAPY AND PROPHYLAXIS

No speciﬁcantiviral therapy. Measlesvaccine, either aloneor combined

with mumps and rubella, is an effective prophylactic measure. After

exposure, humanimmunoglobulin givenup to3–5 days afterexposure is

effective.

LABORATORY DIAGNOSIS

Antigen-capture measles-speciﬁcIgM antibody assays areavailable and

are highly speciﬁc and sensitive. Conﬁrmation of the diagnosis by

demonstration ofa 4-foldrise inmeasles-speciﬁc IgG antibodiesin acute

and convalescent sera. Virus can be isolated fromthroat, conjunctiva

and urine(not routinely used).

Figure 14.1 MEASLES VIRUS(MEASLES)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

After an incubation period of approximately10 (range 8–15) days, patients

develop fever, cough,coryza and conjunctivitis whichincrease in severity for

2–4 days.On the day priorto the onsetof rash, and for1–2 days afterwards,

Koplik’s spots(2–3 mm diameter,bluish-white dots on anerythematous base

and being pathognomonic of measles) appear on mucous membranes,

especially thebuccal mucosa in 70–80%of patients. After 3–4 daysof illness

a discretemaculopapular rashappears onthe face andneck andspreads to the

trunk, and temperaturerises to 39–408C. Lesionson the trunk and facemay

become conﬂuent by the thirdday and then gradually fade. A ﬁne, brawny

desquamation appears7–8 daysafter onsetof therash, but isoften notnoticed

in childrenwho are frequently bathed.

Differential diagnosis. Other viral infections havebeen mistaken for measles

(parvovirus B19, rubella, enteroviruses, dengue, adenoviruses and Epstein–

Barr). Other rash illnesses that have been confused with measles include

eritherm multiforme, toxic shock syndrome, leptospirosis, Rocky Mountain

spotted feverand scarletfever, but theseillnesses donot have thesame clinical

proﬁle ofmeasles with a prodromalrespiratory infection andincreasing fever

for 2–4days prior to onsetof rash.

CLINICAL COURSE

In theabsence ofcomplications the clinicaldisease is usuallyimproving bythe

third dayof rashand resolvesby 7–10 days.A mildmodiﬁed courseof measles

may benoted 1 weekafter vaccination orwhen immuoglobulin isgiven in the

incubation period. A moresevere form of measles, dominated by high fever

and haemorrhages from skin and mucosa, occurs rarely. Among persons

suffering fromprotein malnutrition the lethalityis high.

COMPLICATIONS

The mostcommon complications affectthe respiratorytract and includeotitis

media, laryngotracheobronchitis (croup) and interstitial pneumonia. Otitis

media occursin 5–25%of children lessthan 5 yearsof age.Pneumonia is seen

in 5–10%of children under5 years, andmore frequently inadults. Diarrhoea

occurs inapproximately 10%of young children,croup less frequently,but the

latter maybe severe andlife-threate ning.A persistent diarrhoeawith protein-

losing enteropathyand (subsequentworsening of) ensuingmalnutrition is seen

in developingcountries. Thrombocytopenicpurpura has beenreported onrare

occasions andcomplications involving other organsystems have occasionally

been seen. Encephalitis occurs in 1 per 1000 infected children. Subacute

sclerosing panencephalitis(SSPE), a slowly progressiveCNS infection, occurs

in anaverage of 5–20per million children whohave had measles;the onset is

delayed anaverage of 7years after measles.The illness lastsfrom 1 to3 years

and inevitablyleads to death.For measles thecase-fatality rate averages3 per

1000 children in the USA and between 3 and 30% of young children in

developing countries.

THE VIRUS

Measles virus(Figure 14.2) isan envelopedRNA virus belongingto the genus

Morbillivirus withinthe Paramyxoviridae family.The virus isrelated to can ine

distemper virus. Other members of genus have been shown to cause severe

disease in mammals, e.g. seals and horses.

Measles isa single-strandedvirus of negative

polarity surrounded by the nucleoprotein

(NP), the phosphoprotein (P), the matrix

protein (M) and a large (L) protein wi th

polymerase function. The envelopecontains

the two viral glycoproteins: the haemagglu-

tinin (H)and thefusion (F)protein. The His

responsible for the bindingof measles virus

to cells andthe F protein for the uptakeof

virus intothe cells.Antibodies to Hcorrelate

with protection against disease. Sequencing

data ofthe genescoding forthe H,NP and F

proteins indicatea gradual change instrains

isolated in various parts of the world.

However, measles virus vaccines based on

viruses isolated more than 30 years ago

continue to confer immunity. SSPE isolates obtained by co-cultivation

produce eithera defective M proteinor no Mprotein.

EPIDEMIOLOGY

Persons are most infectious duringthe prodromal phase of illness when the

virus istransmitted through aerosol droplets.Airborne transmission hasbeen

well documented.Most casesoccur in thelate winterand early spring,but low

levels of transmission continueto occur year-round in most climates. Inthe

tropics, mostcases are seen duringthe dry season. Whenthe measles virus is

introduced intoa non-immune population,90–100% become infected and get

clinical measles.Epidemics of measlesoccur every 2–4 yearswhen 30–40% of

children are susceptible. Immunity is lifelong. After the introduction of an

effective vaccine, casereports have fallen by over90%, widespread. Prior to

widespread immunization, most cases inindustrialized countries occurred in

100

Figure 14.2 MEASLES

VIRUS. Bar,100 nm

(Electron micrograph

courtesy ofD. Hockley)

children aged4–6 yearsand insmall childrenin developingcountries. Intensive

immunization coverage has resulted in a shift in age distribution, with

relatively morecases among olderchildren, teenagers and youngadults. With

widespread implementationof two-dose vaccinationstrategies, measles isnow

nearly eliminatedin most European andLatin American countries.However,

if a highvaccine coverage rate (495%)is not upheld after measleshas been

eliminated inthe community, accumulationof susceptibles willinevitably lead

to recurrenceof outbreaks orepidemics fromimported cases aslong as global

eradication ofmeasles is not yetachieved.

THERAPY AND PROPHYLAXIS

Supportive therapy only is indicated for most well nourished children.

Antibiotic treatment is indicated for bacterial otitis media and pneumonia.

Vitamin A(100,000 unitsfor lessthan 12months of age,200,000 unitsfor over

12 months of age)has resulted in 50% reduction ofmortality in developing

countries. Insevere cases (including immunocompromisedchildren), ribavirin

has beenadministered systemically basedon in vitrosusceptibility testing, and

some children haveshown evidence of clinical response. Human immunoglo-

bulin administeredafter exposurein adose of0.25 ml/kgmodiﬁes thedisease in

most children ifgiven within 3–5 days afterexposure. A dose of 0.5ml/kg is

recommended for immunocompromised children. An attenuated measles

vaccine isavailable either asa singleformulation or combinedwith attenuated

mumps andrubella viruses (MMR).About 98%of children immunizedat the

age of 12–15 months develop an antibody response and vaccine efﬁcacy is

590% following a single dose. A seconddose, given later in life, increases

immunity to approximately 99%. 6–15 days after immunization 5–15% of

children willdevelop amild feverand/or rash.Neurological complications(e.g.

encephalitis) occur in less than1 in a million vaccinees. Most immunocom-

promised children should not receive the vaccine, but vaccination is

recommended for HIV-positivechildren without severe immune suppression.

Pregnancy is a contraindication to vaccination. Rare cases of immediate

hypersensitivity have occurred to the gel stabilizer. The administration of

passive antibody up to 12 weeks beforevaccination will blunt or block the

immune responsedependent on the doseof immunoglobulin administered.

LABORATORY DIAGNOSIS

Antigen-capture measles-speciﬁc IgM antibody assays (ELISA) have been

developed, andwhen used appropriately arehighly sensitive andspeciﬁc. The

testbecomes positive within48 hoursafter rashand mayremain positivefor up

to 30days after the onsetof illness. The standard methodfor conﬁrming the

diagnosis isdemonstration of a 4-foldrise in IgG measlesantibodies in acute

and convalescentsera. Haemagglutination–inhibitiontests or ELISAantibody

assaysare most practical, but plaquereduction neutralizationtests arethe most

101

sensitive and speciﬁc. The virus has been isolated from respiratory tract

secretions and rarely from urine or circulating lymphocytes during the

prodromal phase of illness or within a few days after the rash onset.

Immunoﬂuorescence staining of nasalor throat secretions or urine hasbeen

successful, but is not widely available. SSPE is conﬁrmed based on

characteristic EEG patterns and demonstration of measles antibody in the

cerebrospinal ﬂuid (CSF) withan increased CSF to serum measles antibody

ratio, orby demonstration of virusin brain tissue.

Very highmeasles antibody titres aside fromacute infection and SSPEare

regularly seen in autoimmune chronic active hepatitis and occasionally in

systemic lupuserythematosus.

102

A TIMETO AVOID INFECTION

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

15. RUBELLA VIRUS

German measles;Ger. Ro

teln; Fr.rube

ole.

G. Haukenes

Rubella is a mild exanthematous, moderately contagious disease.When the

disease isacquired by the motherduring the ﬁrst 4months of pregnancy, the

virus mayinfect the fetus andcause serious malformations.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Transmission occursby dropletinhalation. The incubationperiod is 2–3

weeks. Thepatient isinfectious from7 daysbefore andup to7 days after

the appearanceof the rash.A child with congenitalrubella may excrete

virus forup to 2 years.

SYMPTOMS AND SIGNS

Systemic: Low-Grade Fever,Mild Malaise

Local: Rash, Enlarged and TenderLymph Nodes

(Suboccipital, Postauricular,Posterior Cervical)

Other: See Complications

The rashlasts for 3–4 days,the lymphadenopathy somewhatlonger.

COMPLICATIONS

Postinfectious encephalitis,purpura, arthralgia, congenital rubella.

THERAPY AND PROPHYLAXIS

No speciﬁc antiviral therapy. Theeffect of speciﬁc immunoglobulin is

uncertain. Vaccineprovides about 95% protection.

LABORATORY DIAGNOSIS

Antibodies can be detected within a few days of appearance of rash.

Diagnosis isbased on seroconversionor risein titre inpaired sera taken

105

at 1–2week intervals, or bydemonstration of speciﬁc IgM.Presence of

antibodies indicates immunity to clinical reinfection. In congenital

rubella, viruscan beisolated frompharynx or urinefor aperiod ofup to

2 years,and speciﬁc IgM isusually present atbirth.

106

Figure 15.1 RUBELLA VIRUS(POSTNATAL RUBELLA)

CLINICAL FEATURES

POSTNATAL RUBELLA

SYMPTOMS AND SIGNS

Transmission occursby dropletinhalation. The incubationperiod is2–3 weeks,

but maybe prolonged afteradministration of speciﬁcimmunoglobulin. Many

cases run asymptomatically or atypically (without rash).Mild conjunctivitis

and feverare sometimes observedas prodromes, especiallyamong adults.The

rash, whichis pinpointmaculopapular, spreads fromface toneck andover the

trunk as pink, slightly raised macules, which may c oalesce. There may be

petechiae on the soft palate, conjunctivitis and mild catarrhal symptoms.

Posterior cervical,postauricular and occipitallymph nodes are oftenenlarged

andtender. Theswelling maypersist for2–3 weeks.Fever islow gradeor absent

during therash. Somepatients have amore generalizedlymphadenopathy and

splenomegalywith slightfever duringtherash, butthe generalcondition isgood.

Thewhite cellcount isloweredwith increasedplasma cellsanda relativeincrease

in both small and large atypical lymphocytes (Tu

rk cells).

Differential diagnosis. Otherexanthematou sinfections: measles, scarlet fever,

exanthema subitum, erythema infectiosum, infectious mononucleosis, echo-

virus and coxsackievirusinfections. In particular, the possibility oferythema

infectiosum (parvovirusB19) should be consideredas both virusesmay infect

the fetus and may manifest with rash, suboccipital lymphadenopathy and

arthralgia, and serological cross-reactivity in the IgM assay has been seen.

There is noclinical picture that is pathognomonicfor rubella. The diagnosis

can bemade with certainty onlyby serological tests.

CLINICAL COURSE

The rash rarely persists for more than 3 days. In about 40% of cases the

infection isasymptomatic. Immunity toclinical and intrauterine reinfectionis

lifelong.

COMPLICATIONS

Postinfectious encephalitisis rare(1 in5–10,000) andsequelae are seldomseen.

Arthralgia isoften seenin adultwomen andmay persistfor weeksand months.

Some patientshave transient thrombocytopenic purpura.

CONGENITAL RUBELLA

Rubella virus mayinfec tthe placenta and the fetus. About30% of children

born to mothers who have acquire d rubella during the ﬁrst trimester of

pregnancy will havecongenital defects at birth.The risk approaches 100%if

107

rubella occurs in the ﬁrst month, but falls to about 10–20% in the fourth

month. Laterin pregnancy,the riskof serious damageto thefetus is low.Rare

cases ofcongenital rubellahave beenreported when themother hadrubella up

to 1month before becomingpregnant. In about15% of casesinfection of the

fetus leads to spontaneousabortion. The classical triad of malformations in

congenital rubella involves the eye (cataract, microphthalmia, glaucoma,

chorioretinitis), the heart (most often patent ductus arteriosus) and the ear

(unilateral or bilateral sensoryneural deafness). Psychomotor retardation is

also commonlyseen. Mostaffected infants havea lowbirth weightbut normal

body length.Purpura, hepatosplenomegaly,hepatitis, anaemiaand pneumonia

may bepresent.

Differential diagnosis. This includes other intrauterine infections such as

toxoplasmosis, syphilisand CMV infection. Theprecise diagnosis is madeby

serological testsand demonstration of virus.

THE VIRUS

Rubella virus(Figure 15.2)is apositive-sense single-strandedRNA virusof the

genus Rubiviruswithin theTogaviridae family.The virion ismedium-sized with

an outer lipoprotein membrane(‘toga’). Three structural proteins have been

identiﬁed, ofwhich twoare glycoproteins locatedin the envelope(E1 andE2),

and the thir d is a non-glycosylated core

protein (C). Only one antigenic type of the

virus is known. The structural proteins are

cleaved from a precursor protein translated

for subgeno mic 24S mRNA. E1 and E2

become N-glycosylated in theendoplasmatic

reticulum. Virusmatures bybudding fromthe

plasma membrane of intracytoplasmic

membranes. The virus may be grown in a

wide range of cell cultures, with or without

cytopathic effect. The fetal damage seen in

congenital rubella seems to bepartly due to

virus-induced retardation of cell division

which, when it occurs in the early phase of

organogenesis, maylead toserious malforma-

tions. In addition, some endothelial damage

and cell necrosisare seen. Infection of thefetus before the immune response

hasbeen established resultsin persistenceof virusthroughout gestationand for

months oryears after birth.

EPIDEMIOLOGY

Rubella is worldwide in distribution. In postnatal rubella the patient is

considered tobe infectiousfrom upto 7days beforeto 7days after theonset of

108

Figure 15.2 RUBELLA

VIRUS. Bar,50 nm(Electron

micrograph courtesyof

E. Kjeldsberg)

rash. Transmission occurs by droplet inhalation. Children with congenital

rubella mayshed largeamounts of virusin the pharynx,faeces andurine for a

long period(up to 2years). Epidemics ofrubell aof 1 to2 years’ durationare

seen at about5 year intervals. During an epidemic thereare about 10 times

more casesthan in theinterepidemic period. Intemperate climates most cases

are seen in spring and early summer. The disease is mostprevalent among

children of5–10 years of age.At puberty about two-thirdsof all childrenare

seropositive. Serologicalexamination of pregnant womenshows that 80–95%

of them are seropositive. Susceptible pregnant women usually contract the

disease from (their own) children. Teachers in kindergartens and primary

schools are professional groups at special risk. Vaccination of girls before

puberty and special risk groups aims to render most childbearing women

immune. However, such immunization programmes lead to only moderate

reduction in the amount ofvirus circulating in the community. Vaccination

coverage willusually notexceed 90%and thereforesome fertile womenremain

susceptible andat risk. Many countrieshave therefore implementeda routine

immunization programme for all infants at theage of about 15 months, in

some countries followedby revaccination of both sexesbefore puberty. As a

result, very fewcases of rubella are seen,and the cases of congenital rubella

may becompletely avoided within afew years inthese countries.

THERAPY AND PROPHYLAXIS

There is no speciﬁc antiviral therapy. In congenital rubella the disease

manifestations at birth may require hospital treatment. Some of the

malformations are treated surgically. High-titre rubella immunoglobulin

seems to have a certain protective effect when given early after exposure.

Administration ofimmunoglobulin may leadto asymptomatic infectionand a

prolonged incubation period. This has to be taken into accountduring the

serological follow-up that should be carried out in thesecases. The vaccine

consists of liveattenuated virus cultivated in a human ﬁbroblastdiploid cell

line. Vaccination provides long-lasting immunity in about 95% of those

vaccinated. Side-effects suchas mild rubella symptoms areseen in 20%, and

arthralgia occurs especially in women. There are no contraindications to

vaccination other thanthose against the useof live virus vaccinesin general:

immune deﬁciency, active infection and pregnancy.Fetal infection has been

observed in a very few cases after inadvertent vaccination of seronegative

pregnant women, but no teratogenic effects of the vaccine have been seen.

Nevertheless, women should not become preg nant in the 3 months after

vaccination. Thevaccine isdispensed as amonovalent vaccineor as atrivalent

vaccine togetherwith measles and mumpsvirus (MMR).

LABORATORY DIAGNOSIS

Postnatally twodiagnostic problems mayarise, acute infectionand immunity.

The clinicianshould thereforealways state theclinical problem,so that proper

109

diagnostic methods can be chosen. In acute infection, serum sample(s) are

examined for the presenceof speciﬁc IgM using an indirect or IgMcap ture

ELISA. If an indirect ELISA is used, measures should be taken to avoid

interference by rheumatoid factor (absorption of IgG). The IgM (anti-m)

capture method is general ly considered to be the most speciﬁc one. IgM

antibodies canbe demonstrateda fewdays afterappearance ofrash andpersist

for about 3months. Also IgG (anti-E1) antibodies appear earlyand usually

persist for life. Occasionally a positive IgM test is seen in infectious

mononucleosis (if the capture assay is used, preabsorption of heterophile

antibodies bysheep red cellscan beattemp ted),in autoimmunechronic active

hepatitistype 1 andin parvovirusB19 infection.A positiveIgM testis alsoseen

in somecases of reinfection. Inearly pregnancy it isof crucial importance to

exclude causesof apositive IgMtest otherthan aprimary rubellainfection. An

IgG seroconversionproves a primaryinfection. Since antibodiesto E2 appear

several weeksafter therash, anti-E2seroconversion mayalso be lookedfor (by

passive haemagglutination based on E2-coated erythrocytes or by Western

blot). SeveralIgM ELISAs shouldalso betried. Immunity maybe screened by

several methods (ELISA,latex agglutination, HI) which speciﬁcallydetect at

least 15 international units (I.U.) of anti-E1 antibodies. In most cases of

autoimmune chronic active hepatitis very high levels (up to90,000 I.U.) of

anti-E1IgG rubella antibodies(and/or measlesantibodies) areseen, whichmay

be of differentialdiagnostic value versus primary biliary cirrhosis wherelow

titres arefound.

In congenitalrubella virus may beisolated from urine andpharynx using a

rabbit kidney (RK13) or cornea (SIRC) cell line. Whencytopathic changes

appear, thevirus can beidentiﬁed using theimmunoﬂuorescence method. The

ﬁnding ofIgM antibodies andpersistence or riseof IgG antibodiesduring the

ﬁrst yearof life is alsodiagnostic of congenitalrubella.

110

A DAYOUT FOR THEADENOVIRUS FAMILY

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

16. ADENOVIRUSES

The nameoriginates from adenoids, thenasopharyngeal lymphoid tissue

from whichvirus was ﬁrst isolated.

I. Ørstavikand D. Wiger

Adenoviruses causeinfection ofthe respiratory tract,the eyeand the intestine.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

The infection is transmitted by droplets or by contact with virus-

contaminated objects (e.g. hands, towels, medical equipment). The

incubation period varies from 5 to 10 days. The patient is usu ally

contagious aslong as the symptomslast.

SYMPTOMS AND SIGNS

Systemic: Fever

Respiratory: Nasopharyngit is,Occasional Pneumonia

(Especially inInfants)

Ocular: Keratoconjunctivitis, Conjunctivitis

Gastrointestinal: Diarrhoea, Vomiting

Respiratory symptoms lastfor about 1 week,ocular symptoms for 2–8

weeks andgastrointestinal symptoms for upto 10 days.

COMPLICATIONS

Rare fatal cases of pneumonia and disseminated adenovirus infection

have beenreported. Permanent opacity ofcornea is rare.

THERAPY AND PROPHYLAXIS

There isno speciﬁctreatment. Avaccine hasbeen usedfor immunization

of militaryrecruits.

113

LABORATORY DIAGNOSIS

Adenoviruses can be detected by isolation in nasopharyngeal and

conjunctival secretions and throat washings and are seen by electron

microscopy offaeces during theacute phase ofthe disease. Arise inCF

antibodies toa commonantigen is usuallyseen in respiratoryinfections.

Viral antigens mayalso be detected in clinicalspecimens using various

immunological techniquesand PCR.

114

Figure 16.1 ADENOVIRUS (RESPIRATORYINFECTION)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

The incubat ionperiod isusually between5 and10 daysand variesaccording to

the infectivedos eand the clinical manifestation.The patient is contagiousas

long asthe symptoms last, butthe virus maypersist in tonsils andadenoids.

Respiratory disease. Inacute upper respiratory tract infectionssymptoms are

fever, nasal congestion andsore throat with a cough. This type ofinfection

occurs most often inpreschool children, although about 50% of adenovirus

infectionsin this agegroup areasymptomatic. Seriousbronchopneumonia may

occasionally occur,especially in infants.

Acute respiratory disease (ARD) occurs in epidemics primarily among

military recruitsabout 3–4 weeks afterthey have enteredservice. Sore throat,

cough andfever last about1 week.Lung inﬁltrations maybe found, butovert

pneumonia israre.

Pharyngoconjunctival fever often occurs in children and presents with

pharyngitis, conjunctivitis and fever, often accompanied by rhinitis, otitis

media and/ordiarrhoea. Exudate may bepresent on thetonsils and posterior

pharyngeal wall.Cervical lymphadenopathy is common.

Oculardisea se(without respiratorysymptoms). Afollicular conjunctivitisis seen

with oedema of periorbital tissue, redness of the conjunctivae and serous

exudation. Recoveryis usually complete.

Epidemic keratoconjunctivitis(EKC) starts asan acuteunilateral conjuncti-

vitis that ofteneventually involves both eyes. Preauricular lymphadenopathy

withsome tenderness isobserved. Subepithelialopacities inthe corneamay last

from 2to 8 weeks, occasionallyyears, or permanently.

Gastrointestinal disease. Infantile diarrhoea gives moderate diarrhoea,

vomiting andfever.

Certain adenoviruses have been associated with haemorrhagic cystitis,

intussusception ininfancy and a whoopingcough-like disease.

Persistent andsometimes severeinfection withcertain adenoviruses hasbeen

observed in AIDS patients and in other immunocompromised individuals.

Severe adenovirus infections have been observed in children with severe

combined immunodeﬁciency(SCID).

In pharyngitis and ARD, differential diagnoses are infections with

Streptococcus pyogenes, mycoplasma, chlamydia (psittacosis), coxiella (Q-

fever) andvarious respiratory viruses.An infectionwith S. pyogenesis usually

more aggressiveand involves primarily thetonsillar tissue. Pharyngoconjunc-

tival feveroften occurs in epidemicform and is usuallyeasier to diagnose.In

follicular conjunctivitisbacteria (Chlamydiatrachomatis) shouldbe considered.

Epidemic haemorrhagic keratojunctivitisis usually caused by enterovirus 70,

while unilateral keratitiswithout conjunctivitis suggests herpes simplexvirus.

115

Laboratory conﬁrmation is necessary in order to establish a deﬁnite

aetiological diagnosis.

CLINICAL COURSE

Gastroenteritis lasts up to 10days and uncomplicated respiratory infections

about 1week. The eye infectionmay persist for2–8 weeks or longer.

COMPLICATIONS

Secondary bacterialinfections (otitismedia and sinusitis)are occasionallyseen

in cases of respiratory tract infections. Some cases of lung ﬁbrosis and

bronchiectasis have been reported, especially in connection with serotype 7

infections. Keratitismay inrare caseslead topermanent opacitiesof thecornea

with impairmentof vision.

THE VIRUS

Human adenovirusesare medium-sizednon-enveloped viruses witha diameter

of about80 nm(Figure 16.2) and include47 different species(serotypes). The

virus capsid is an icosahedral shell made up of 252 capsomers, 240 hexon

capsomers and 12 pentoncapsomers atthe verticesof theicosahedron. Pentons

have antenna-like projections(ﬁbres )which vary in length dependingon the

subgenus of virus. Thevirus capsidencloses a

double-stranded DNAprotein complex, and

the virus contains at least 10 different

polypeptides. The human adenovirus genus

consists of 47 or more serotypes which are

divided into six subgenera (A–F), basedon

DNA homology.The viruses inthe different

subgenera oftenshare biological,clinical and

epidemiological characteristics. The type-

speciﬁc antigens are located on the outside

of the hexons and the ﬁbres.Antib odiesto

these antigens seem to be protective and

probably last throughout life. The virus

serotype is based onvirus neutralization by

antibodies against these antigens. Human

adenovirus commongroup antigens are also

found on the hexons, but are probably

located internally. Thesecross-reacting anti-

gens, believed not to stimulate protective antibodies, are used in CFT and

ELISA. Adenoviruses aresomewhat resistant to manyphysical and chemical

agents. Because of this, virus is easily spread by contact with virus-

contaminated equipmentand water.

116

Figure16.2 ADENOVIRUS.

Bar, 100nm (Electronmicro-

graph courtesy of E. Kjelds-

berg)

EPIDEMIOLOGY

Virus isspread by thefaecal–oral route, especiallyin families. Therespiratory

route (aerosols) hasbeen shown to beimportant in the spreadof respiratory

infections amongmilitary recruits.The eye isalso animportant portalof entry

for certain adenoviruses. Adenoviruses 1, 2, 5 and 6 are endemic among

preschool children and are associated with respiratory disease in this age

group. Theseviruses are knownto give prolonged infectionsof the lymphatic

tissue inthe throatand intestine,with continual orintermittent virusshedding.

Because of this, isolationof these viruses will not always be diagnosticof a

current infection. Adenoviruses 3, 4, 7, 14 and 21 have caused epidemic

outbreaks of respiratory disease among militaryrecruits as well as sporadic

infections in the civilian population. Conjunctivitis has beenreport edto be

causedby serotypes 1,2, 3,4, 6,9, 10,15, 16,17, 20,22 and29. Adenoviruses8,

19 and37 havemost often beenassociated with epidemickeratoconjunctivitis.

Contaminated ophthalmologicalinstruments (especiallytonometers) havebeen

implicated inthe spread ofthis disease. Intrafamilialspread of theseviruses is

also important.Adenoviruses 40 and41 causediarrhoea and feverin children.

Cases withadenovirus 41tend torun aprotracted course. Infectionswith these

faecal adenoviruses areless often associated with respiratorysymptoms than

other types of adenoviruses. Many adenovirus species are isolated only

occasionally, andlittle isknown about theirmedical importance.Outbreaks of

respiratory disease dueto adenoviruses among militaryrecruits occur mostly

during thewinter months in temperateareas, while adenovirusgastroenteritis

is most frequently observed during the late autumn and winter. Otherwise,

there seems to be very little seasonal variation in the occurrence of

adenoviruses.

THERAPY AND PROPHYLAXIS

Speciﬁc antiviral chemotherapy or immune therapy is not available, and all

treatment is symptomatic. Avaccine against certain types of adenovirushas

beengiven to militaryrecruits insome countries.Because nosocomialspread of

adenovirus respiratory infections and gastroenteritis occurs quite often,

isolation of patients in hospital is important. The spread of epidemic

keratoconjunctivitis can be prevented by strict hygieneduring eye examina-

tions andby sterilizationof equipment. Thespread of viruswithin households

may becontrolled by hygienic measuressuch as careful handwashing.

LABORATORY DIAGNOSIS

Samples forvirus isolationshould betaken as earlyas possiblein thecourse of

the disease. Virus can be isolated in cell cultures from throat swabs,

nasopharyngeal washings, rectal swabs and faeces from patients with

respiratory infections. Virus isolation from the eye is usuall y made from

117

swabs ofthe lowerconjunctival sacor fromconjunctival scrapings.Isolation in

cell culturetakes from a few daysto 2–3 weeks. Theadenoviruses that cause

gastroenteritis oftengrow verypoorly ornot atall inconventional cellcultures.

These virusesmay be detected directlyin faeces byelectron microscopy or by

immunological techniques such as latexagglutinatio nor ELISA. Virus may

also be detected by PCR. Rapid identiﬁcation of adenovirus antigen in

nasopharyngeal secretions,conjunctival scrapings or cellsediment from urine

is alsopossible by immunoﬂuorescence andELISA. The CFantibody titre of

infected patients (adults) shows a 4-fold or greater rise in paired sera. CF

antibodies do notpersist for long periodsunless there are reinfections. More

sensitive techniques, suchas ELISA, may be necessaryto detect the immune

response toadenoviruses insmall children. Infectionsof theeye alone maynot

give antibodytitre rises detectable byCF tests.

118

RAPID SPREAD—DIARRHOEAON WHEELS

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

17. ROTAVIRUSES

Lat. rota¼ wheel,reﬂecting its electronmicroscop icappearance.

I. Ørstavikand E. Kjeldsberg

Rotaviruses causeacute, often febrile gastroenteritis.The disease occursmost

often inchildren, but mayaffect otherage groups. Intemperate climates most

cases occurduring winter/spring.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

The infectionis spreadby the faecal–oralroute. Viralexcretion in faeces

may lastfor 4–7 days after onsetof illness. Theincubation period is2–3

days.

SYMPTOMS AND SIGNS

Systemic: Fever (OftenHigh-Grade)

Local: Diarrhoea, Vomiting

The illnessusually lasts for 4–7days. Complete recoveryis the rule.

COMPLICATIONS

Febrile convulsionsmay occur in smallchildren.

THERAPY AND PROPHYLAXIS

No speciﬁc therapyis available, but it isoften necessary to correct the

patients’ ﬂuid–electrolyte balance. Hospitalization may be necessa ry.

Strict hygienicmeasures are needed toavoid further spread.

LABORATORY DIAGNOSIS

Rotavirus infection is diagnosed by demonstrating viral antigens by

ELISA orlate xagglutination, or viral particlesby electron microscopy

of faecalsamples.

121

122

Figure 17.1 ROTAVIRUSES (GASTROENTERITIS)

CLINICAL FEATURES

SYMPTOMS AND SIGNS

After anincubation period of 2–3days the illness usuallybe ginswith nausea

and vomiting, followed by diarrhoea within 24 hours. Vomiting lasts for a

short period, and is absent in some cases. In severe cases the stools are

frequent, watery, voluminous and foul-smelling. Fever is commonlypresent

and may be high-grade. In children febrile convulsions may occur.

Dehydration ismost often isotonic, butmay be hypotonic, particularly when

the patient has been given ﬂuid deﬁcient in electrolytes (e.g. juice). Visible

blood in thestools is almost never observed. Thewhite cell count is normal

with relativelymphocytosis and transientneutropenia. An importantfactor in

the pathogenesisof a rotavirusinfection is lowered disaccharidasefunction in

the gut.Disaccharides (lactose, sucrose) remain unabsorbedin the gut lumen

and cause dehydration by osmotic pressure. Many patients with rotavirus

gastroenteritis alsohave symptomsof upperrespiratory tractinfection, butit is

not clearwhether this is causedby rotavirus.

Differential diagnosis. Thetriad of vomiting, diarrhoea andfever is a typical

ﬁndingin rotavirus gastroenteritis,but maybe seenin gastroenteritiscaused by

other infectious agents. In shigellosis and salmonellosis there is usually

leukocytosis/granulocytosis in peripheral blood, suggestive of a bacterial

aetiology,an dthere maybe visibleblood inthe stools.In gastroenteritiscaused

byEscheri chiacoli vomitingand feverare infrequent.Gastroenteritis causedby

otherviruses (adenovirus, astrovirus,calicivirus, Norwalkagent, etc.)is usually

less severe than rotavirus gastroenteritis. However, as the symptoms and

severity of rotavirus gastroenteritis may vary considerably, virological

examination isnecessary in order toobtain an aetiological diagnosis.

CLINICAL COURSE

The illness usually lasts 4–7 days, but cases have been described with

protracted diarrhoeaand virus excretion.The upperpart of thesmall bowel is

the main site for rotavirus infection, and damage to thedistal parts of the

intestinal villiwith decreasing enzymesecretion probably causesa malabsorp-

tion resultingin diarrhoea.Serological studieshave shownthat many rotavirus

infections are asymptomatic. Without dietary measures the course is often

protracted, withrecurr entbouts of diarrhoea. Severecases with dehydration,

hypotonia andshock mayhave afata loutcome ifthe patientis not adequately

rehydrated. Otherwiserecovery is complete.

COMPLICATIONS

The onlycomplication is febrile convulsionsin children.

123

THE VIRUS

Rotaviruses aremembers of thegenus Rotavirus within thefamily Reoviridae.

The name of thevirus is derived from the Latin word rota,meaning wheel,

reﬂecting its shape as seen in the electron microscope. The intact virion of

about 102nm in diameter displays spikes from a smooth surface of about

79nm (Figure 17.2(a)). When stools of patients are examined by electron

microscopy, however, incomplete virus particles predominate, often without

the smoothouter layer (Figure17.2(b)). The virions containa central double-

stranded RNA consisting of 11

segments. The RNA segments code for

a structural or non-structural protein.

The antigenicstructure andclassiﬁcation

of rotaviruses are complex. At present

six groups (A–F) are considered. Most

rotaviruses found in humans belong to

group A, but infections with groups B

and C have alsobeen reported. Group-

and subgroup-speciﬁc antigens are

located on the inner capsid layer,

whereas type-speciﬁc antigensare found

on the outer layer. Among group A

rotaviruses, two subgroupsand 12 sero-

types have been described, ofwhich six

serotypes have been found in man. A

typing system based on two structural

proteins (G+P) is used, and of at least 14 group AG types, 10 have been

detected in humans. The segmented genome must account for the complex

antigenic properties of the rotaviruses, allowing reassortation of the 11

segments of RNA in cells being doublyinfected with different strains. This

mechanism isalso described forinﬂuenzavirus. Rotaviruses areinactivated by

heating to 1008C or treatment with acid (pH53), glutaraldehyde (3%) or

alcohol (470%),while iodoform is lesseffective.

EPIDEMIOLOGY

Rotavirus infections occurall over the world. The majorityof children have

antibodies by the age of 5. Most clinical cases occur in children between

6months and3 years ofage. Rotavirusis endemic,but intemperate zonesmost

cases occurin winter/spring. In tropicaland subtropical areasreports suggest

that most cases occur during the rainy season. Up to 50% of hospitalized

children withgastroenteritis are infectedwith rotavirus.The virus isspread by

the faecal–oralroute, but the rapidspread of the infectionwithin institutions

with highhygienic standards suggeststhat the virus isalso spread bydroplets

from the throat, although this is not proven. Most newborn infants below

124

(a) (b)

Figure 17.2 ROTAVIRUS: TWO

MORPHOLOGICAL FORMS(SEE

TEXT) (Electron micrograph

courtesy ofE. Kjeldsberg)

6months of ageare probablyprotected bycirculating maternalantibodies and/

or byfactors inbreast milk.One individualmay become infectedwith different

rotavirus serotypes and also be reinfected with the same serotype. Thus,

although type-speciﬁc neutralizingantibodies are formed following infection,

the protectiveeffect may notbe long-lasting. Extensiveoutbreaks of rotavirus

gastroenteritis havebeen observed inhospitals andother institutions, andin a

family setting there is often more than one case of illness in the same

household. Mostcases ofhuman rotavirus gastroenteritisare caused bygroup

A rotaviruses. Group B virus es have caused large epidemics in China.

Rotavirus gastroenteritis causesa large number of deaths amongchildren in

developing countries,whereas fatal casesare very rarein developed countries.

THERAPY AND PROPHYLAXIS

There is nospeciﬁc therapy. Symptomatic treatmentappropriate for cases of

acute gastroen teritis should be given with particular emphasis on oral

rehydration with glucose–electrolyte solution. Milk may maintain the

diarrhoea (see above),and should be omittedfrom the diet duringthe whole

course of theillness. Admission to hospital shouldbe considered if there are

severe symptomsor ifthe patient isvery young.Reports on vaccinationas well

as on the use ofimmunoglobulin prophylaxis have been published, but such

measures arenot generallyavailable. An oralrotavirus vaccine forinfants was

introduced inthe USAin 1998, butwas withdrawn thefollowing yearbecause

it wasassociated with an increasedrisk of intussusception. Whena patient is

treated at home, those caring for the patient should wash their hands

frequently andwash carefully all itemsthat may becontam inatedwith faeces

and which cannot be boiled.In hospitals, isolation of the patient and strict

hygienic measuresare necessary to avoidcross-infection.

LABORATORY DIAGNOSIS

A specimenof faeces(at least1 cm

) shouldbe obtainedduring theacute phase

of theillness, andsent tothe laboratory withoutany additivesor refrigeration.

Several rapid methodsare available to detectvirus or viral antigensin stools

(electron microscopy,ELISA, latex agglutination,etc.), sothe laboratory may

often beable to reportthe resultson the sameday. Human rotavirusescan be

cultivated inspecial cell cultures onlywith difﬁculty. Serological testsare not

used forroutine diagnosis of rotavirusinfections.

125

GET YOURPRIORITIES RIGHT

APractical Guide to Clinical Virology. Edited by L. R. Haaheim, J. R. Pattison and R. J. Whitley

 2002John Wiley & Sons, Ltd.

ISBNs: 0-470-84429-9 (HB); 0-471-95097-1 (PB)

18. HERPES SIMPLEX VIRUS

(HSV1 AND HSV2)

From Greekherpein ¼creeping.

E. Tjøttaand G. Hoddevik

Herpes simplex virus infections occur worldwide. Lifelong latency is

established after the primary infection. Recurrences as herpes labialis

(usually HSV1)and herpes genitalis (usuallyHSV2) occur frequently.

TRANSMISSION/INCUBATION PERIOD/CLINICALFEATURES

Infection bydroplets orcontact is mostcommon. Theincubation period

is 2–12days.

SYMPTOMS AND SIGNS

Systemic: Primary: Fever, Malaise.In Newborn Infants:

Generalized Infectionwith a Septicaemia-

like Picture

Local: Primary: Vesicles inthe Mouth(Gingivostomatitis) or

in theGenital Region, Lymphadenopathy

Recurrent: Vesicles on the SkinNear the Mouth

(‘COLD SORES’)or in the GenitalRegion

Primary HSV1 infec tion is often clinically inapparent, but gingivo-

stomatitis of about2 weeks’ duration occurs. Recurrent genitalherpes

does notlast as long asthe primary infection.

COMPLICATIONS

Keratitismay cause visualﬁeld impairmentand blindness.Encephalitis is

a rarebut seriouscomplication. Disseminated HSVinfection isa serious

complication in immunocompromised individuals. Eczema herpeticum

(Kaposi’s varicelliform eruption) occurs in children with a history of

eczema. Aherpetic whitlow is seenafter accidental inoculation.

127