oxford medicinescsml.rssi.ru/info/ebolavirus/marburg_and_ebola_viruses.pdf · oxford medicine...

Marburg and Ebola viruses

of 23

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). (c) Oxford University Press, 2014. All RightsReserved. Under the terms of the l icence agreement, an individual user may print out a PDF of a single chapter of a title in OxfordMedicine Online for personal use (for details see Privacy Policy).date: 14 October 2014

Publisher: OxfordUniversityPress PrintPublicationDate: Jul2011PrintISBN-13: 9780198570028 Publishedonline: Jul2011DOI: 10.1093/med/9780198570028.001.0001

Chapter: MarburgandEbolavirusesAuthor(s): G.LloydDOI: 10.1093/med/9780198570028.003.0038

OxfordMedicine

OxfordTextbookofZoonoses:Biology,ClinicalPractice,andPublicHealthControl(2ed.)EditedbyS.R.Palmer,LordSoulsby,PaulTorgerson,andDavidW.G.Brown

MarburgandEbolaviruses

Summary

MarburgandEbolavirusescausesevereandoftenfatalhaemorrhagicdiseaseinhumansandnon-humanprimates.TheyarethetwoestablishedmembersofthefamilyFiloviridaeandhaveadistinctivefilamentousandirregularmorphologywithagenomeconsistingofaverylarge(about19kb)single-strandedRNAofnegativepolarity.FeaturesoftheirorganizationandstructureatthemolecularlevelhaveledtotheirinclusioninthetaxonomicorderMononegavirales,togetherwiththeParamyxovirusesandtheRhabdoviruses.

Fromitsoriginaldescriptionin1967to2009,therehavebeeneightreportedoutbreaksofhumanMarburgvirusinfection.ThefirstbeingthreesimultaneousoutbreaksthatoccurredinEuropeatMarburg,Frankfurt,andBelgrade,followingtheimportationofinfectedAfricangreenmonkeys(Ceropithecusaethiops)fromUganda.TheremainingoutbreaksoccurredinSouthAfrica1975;Kenya1980and1987;DemocraticRepublicofCongo(DRC)(1988–2000);Angola(2004–5)andUganda(2007and2008).Theseeightepisodesinvolved449caseswith369deaths,anoverallfatalityrateof82.3%.Allthedeathstodatehaveoccurredintheprimarycases.

Between1976and2009outbreaksofhumanEbolahaemorrhagicfeverhavebeenidentifiedinZaire(1976,1977,1995,2001–2,2003and2007);Sudan(1976,1979and2004);Uganda(2000–1and2007–8);Kenya(1980);Côted’Ivoire(1994and1995);andtheGabon(1996and1997).Allagegroupsandsexeswereaffected.Inaddition,alaboratory-derivedinfectionoccurredduringthestudiesofthe1976ZaireandSudanepidemic.Thereisnoknownendemicincidenceofthediseaseandthemortalityratesarebasedonthelimitednumbersofepidemicsidentified.Thishasinvolved2,292-recordedcaseswith1,524deaths,anoverallcasefatalityrateof66.5%.

AnewstrainofEbolavirusnamedRestonwasisolatedfromanepizooticofdyingcynomolgusmonkeysshippedtotheUSA(1989,1990)andItaly(1992)fromthePhilippines.ThevirusprovedantigenicallyandgeneticallydistinctfromtheAfricanEbolaviruses.HumaninfectionsdocumentedduringtheUSAepizooticprovedasymptomatic.TherewasnoevidenceofanepidemiologicallinkwithAfrica.Therefore,unlikeitsAfricancounterpartsRestonEbolaVirushasproventodatetobenon-pathogenicinhumans.Thehighmortalityamongmonkeysmakesthemanunlikelynaturalreservoirs.However,sixoutof141slaughterhouseworkersstudiedinthePhilippines,whohaddailycontactwithEbolaseropositivepigs,hadantibodiesagainstRestonebolavirus.ThismarksthefirsttimethatRestonebolavirushasbeenfoundinpigs


of 23


andthepossibilityofEbolatransmissiontohumansfrompigstohumans,hasoccurred(Barrette2009;WorldHealthOrganization(WHO)2009).

InAfrica,thetransmissionofhaemorrhagicfevercausedbyEbolaandMarburghasbeenassociatedwiththereuseofunsterileneedlesandsyringes,withtheprovisionofpatientcarewithoutappropriatebarrierprecautionspreventingexposuretovirus-containingbloodandotherbodyfluidsandpreparingbodiesforfuneralsandburial.Inaddition,thekillingandpreparingofnon-humanprimatesforfoodwasconsideredthesourceofSOMPoutbreaks.Epidemiologicalstudiesinhumansindicatethattheairborneroutedoesnotreadilytransmitinfectionfrompersontoperson.Bycontrast,studiesofEbolaandMarburgvirusinfectionsinnon-humanprimateshavesuggestedpossibleairbornespreadamongthesespecies.Theriskofperson-to-persontransmissionishighestduringthelaterstagesofillness.Studiesofindividualswhoareincontactwithaninfectedpatientduringtheincubationperiodindicatethatinfectionriskislow.

AsthenaturalhistoryandreservoiroftheFilovirusesareunknown,therearenospecificprecautionsforavoidinginfectionfromthenaturalenvironment.Non-humanprimatesarenotconsideredthenaturalreservoirofFilovirusesdespitebeingthesourceofMarburgvirusintroducedintoEuropeandEbolavirusesintroducedintotheUSAandItaly.Theprecautionaryquarantiningofnon-humanprimatesimportedfromAfricaandAsiaforaminimumofsixweeksreducesthepossibilityofintroducingaFilovirusinfection.Recently,extensivestudiesundertakentodeterminethereservoirofFiloviruseshaveidentifiedincommonspeciesoffruitbat(Rousettusaegyptiacus)asapotentialcandidate(Swanepoel1996;Towner2007;Pourrut2009).

SincetherearenolicensedvaccinesorspecificantiviraldrugsforthetreatmentofFilovirusinfections,earlyidentificationofinfectedpatientsoranimalsisessential.Preventionstrategiesreducingtheriskoftransmissioninendemicandnon-endemicareasrelyontheintroductionofstrictisolationoffebrilepatientsandrigoroususeofbarrierprecautions.Consequently,manyinstitutionsandexpertsconsiderFilovirusespotentialbiologicalweapons(Borro2002).Filoviruspublichealthandbiodefenceresearchrequiretheuseofmaximum-containmentlaboratoryfacilitieswhereFilovirusesarehandledunderbiosafety-level(BSL)-4containmenttoprotectlaboratoryworkersfrominfection.Thereareonlyafewsuchfacilitiesthatexistworldwide.

History

Filovirusinfectionswereunknownuntil1967,when31humancasesofanacutehaemorrhagicfeveroccurredsimultaneouslyinMarburgandFrankfurt,FederalRepublicofGermany,andBelgrade,formerYugoslavia(Martini1969).Laboratoryworkers,medicalpersonnel,animalcarepersonnelandtheirrelativeswereinfected,sevenofwhomdied.Theprimarycasesoccurredthroughcontactwithkidneytissue,blood,andcellculturesderivedfromVervetorAfricangreenmonkeys(Ceropithecusaethiops)importedfromUganda.Thevirusisolatedfrompatient’sbloodandtissuewasmorphologicallyuniquewhenobservedbyelectronmicroscopy(seeFig.31.1a)andantigenicallyunrelatedtoanyknownmammalianpathogen.ThisviralagentwasnamedMarburgvirus(MBG)afterthecityofMarburg,wheremostofthecasesandinitialworkoccurred.During1975(Zimbabwe),1980and1987(Kenya)thereweresporadicfatalcasesidentifiedprimarilyamongsttourists.TheKenyancaseshadincludedvisitstobatinfestedKitumcavesinKenya’sMountElgonNationalPark(Gearetal.1975;Smithetal.1982;Teepeetal.1983;Johnsonetal.1996)(Table31.1).Apartfromthe1987case,secondaryinfectionsprovedarisktohealthcareworkers.Furtherepidemiologicalinvestigationsintheseareashasrevealednoinformationontheoriginoftheseinfectionsoccurred.

Fig.31.1


of 23


(a)Electronmicrograph,showingfilamentousformsofEbola(Reston)virus(×18360).(b)Ebola(Sudan)virusthinsection,showingvirionsextrudingfromcellsintoextracellularspaces(×14040).

CourtesyofB.Dowsett

Table31.1HumanpathogensintheorderMononegavirales

Family Subfamily Genus Humanpathogens

Rhabdoviridae

Lyssaviru Rabiesvirus

Filoviridae

Marburgvirus Marburgvirus

Ebolavirus Ebolavirus

Paramyxoviridae

Paramyxovirinae

Rubulavirus Mumpsvirus,Parainfluenzavirus2,4

Respirovirus Parainfluenzavirus1,3

Henipavirus Hendravirus,Nipahvirus

Morbillivirus Measlesvirus

Rubulavirus Mumpsvirus,Parainfluenzavirus2,4

Pneumovirinae

Pneumovirus Respiratorysyncytialvirus

Metaneumovirus Humanmetapneumovirus

Betweenlate1998and2000inDemocraticRepublicoftheCongothefirstlargeoutbreakofthisdiseaseundernaturalconditionsoccurred,whichinvolved154cases,ofwhich128werefatal,representingacasefatalityrateof83%.ThemajorityofcasesoccurredinyoungmaleworkersatagoldmineinDurba,inthenortheasternpartofthecountry,whichprovedtobetheepicentreoftheoutbreak.CasesspreadtotheneighbouringvillageofWaste.Familymembersinvolvedintheclosecareofpatientsaccountedforsomecases,butsecondarytransmissionappearedtoberare.

ThelargestMarburgoutbreakinhistoryoccurredbetween2004and2005,inAngola.ItwasbelievedtohavestartedinUigeProvinceinOctober2004thatresultedin252cases,with227deaths(CFR88%)countrywidebyJuly2005.AllcasesdetectedinotherprovinceswerelinkedtotheoutbreakinUige(Towers2006).

FromJunetoAugust2007,threeconfirmedcasesoccurredamongstmineworkersworkinginKamwenge,westernUgandawereidentified.Ofthetwominerswhocaredfortheindexcasewhodied,onealsosufferedafatalillness(WHO2007).

InJuly2008,aDutchtouristdevelopedMarburgfourdaysafterreturningtotheNetherlandsfromathree-weekholidayinUganda.Thesourceoftheexposurehasnotbeendetermined,althoughthewomanhadvisitedcavesinMaramagambo


of 23


ForestwesternUgandaatthesouthernedgeofQueenElizabethNationalpark,wherebatswerepresent(WHO2008;Timen2009).

Therehavebeen414primaryhumanMarburginfectionsdocumentedandanincreasingnumberofsecondarycasesrecordedwhichhaveoriginatedfromanincreasinggeographicrangeinAfrica(Table31.2).

Table31.2Summaryofhumanfilovirusinfectionsduringidentifiedoutbreaks

Year Filovirus Sourceofinfection Allcasesdeaths/total

Overallmortalityrate(%)

Source Comments

1967 Marburgvirus Germany,Marburg 5/23 22.6 Vervetmonkeys

ImportedfromUganda

Germany,Frankfurt 2/6

Yugoslavia,Belgrade 0/2

1975 Marburgvirus Zimbabwe/SouthAfrica(Johannesburg)

1/3 33.3 Unknown IndexcaseinfectedinZimbabwe.Secondarycases:–travellingcompanionandnurse

1976 Zaireebolavirus

NorthernZaire(Yambuka)

280/318 88.1 Unknown Indexcaseintroducedvirusintohospital

1976 Sudanebolavirus

Sudan,Maridi 116/213 53.2 Unknown Diseaseamplifiedbytransmissioninlargeactivehospital

Sudan,Nazara 31/67

Sudan,Tembura 3/3

Sudan,Juba 1/1 OriginatedinNazaracottonfactory


UnitedKingdom,PortonDown

0/1 0 Laboratoryinfection

Needle-stick

1977 (Zaireebolavirus)

Zaire,Tandala 1/1 100 Unknown Tandala


SouthernSudan,Yambo-NazarDistrict,

22/34 64.7 Unknown Nazara,Maridi&localarea

1980 Marburgvirus Kenya,MountElgon 1/2 50 Unknown VisitedKitum


of 23


1980 Marburgvirus Kenya,MountElgon 1/2 50 Unknown VisitedKitumcaveinnationalpark

1987 Marburgvirus Kenya,MountElgon,Kisumu

1/1 100 Unknown ExpatriatetravellinginwesternKenya.VisitedKitumcave

1988 Marburgvirus USSR(Koltsova) 1/1 100 Laboratoryinfection

Associatedwithanimalstudies

1989-1990

Restonebolavirus

US(Alice,Philadelphia,Reston)

0/4 0 Monkeys Epizootic-importedmonkeysfromexportfacilityinPhilippines

1990 Restonebolavirus

Philippines(Luzon) 0/12 0 Monkeys Exportfacility

1990 Marburgvirus USSR(Koltsovo) 0/1 0 Laboratoryinfection



Italy,Sienna 0 0 Monkeys Epizootic-importfromexportfacilityinPhilippinessameasUSoutbreakin1989

1994 Côted’Ivoireebolavirus

Côted’Ivoire,Taiforest

0/1 0 Chimpanzees ContractedinScientistduringpost-mortemofchimpanzee—repatriatedtoSwitzerland

1994-1995

Zaireebolavirus

Gabon(Andok,Mekouka,Minkebe,Mayela-Mbeza,Ovan,Etakangaye)

31/52 60 Unknown


Zaire,Kikwit 245/317 77.3 Unknown ConfinedtoBandundoregionaroundKikwit

1996 Zaireebolavirus-

Gabon(Mayibout,Makokou)

21/37 57 Chimpanzees Contactwithdeadprimateshuntedfor


of 23


huntedforfood


Russia(SergiyevPosad-6)

1/1 100 Laboratoryinfection


1996-1997

Zaireebolavirus

Gabon(Balimba,Boouee,Lastourville,Libreville,Lolo),SouthAfrica(Johannesburg)

46/62 74.2 Chimpanzee? IndexcasehunterNursetreatingimportedcasefromGabontoJohannesburg


USA 0 0 Monkeys Epizootic-PrimatesimportedfromPhillipinestoquarantinefacilityinTexas


Phillipines 0 0 Monkeys Epizootic-IdentifiedinExportfacility.Nohumaninfections

1998-2000

Marburgvirus DemocraticRepublicofCongo(Durba,Watsa)

128/154 83.1 Unknown EpicentreofoutbreakinyoungmalegoldworkersinDurba

2000-2001

Sudanebolavirus

Uganda(Gulu,Masindi&MbararaDisricts)

224/425 52.7 Unknown Spreadthroughattendingfunerals,familycasecontact&medicalcentres

2001-2002

Zaireebolavirus

Gabon(Ekata,Etakangaye,Franceville,GrandEtoumbi,Ilahounene,

53/65 82 Unknown CommunityandNosocomialspreadonborderregionofGabonandCongo

2001-2002

Zaireebolavirus

Congo(Abolo,Ambomi,Entsiami,Kelle,Olloba

43/57 75.6 Unknown


Congo(Olloba/Gabon(Etata))

10/11 90.9 Unknown

2002- Zaire RepublicofCongo 129/143 89 Unknown


of 23


2002-2003

Zaireebolavirus

RepublicofCongo(Mbomo&Kelledistrictsof)

129/143 89 Unknown

2003-2004

Zaireebolavirus

RepublicofCongo(MbomoandMbandzavillagesinMbomodistrictof)

29/35 83 Unknown


Russia(Koltsovo) 1/1 100 Laboratoryinfection

GuineapigadaptedZaireebolavirus

2004-2005

Marburgvirus Angola,UigeProvince

227/252 90.1 Unknown CommunityspreadthroughvariousprovinceslinkedtoUige


Sudan(Yambio) 7/17 41-.2 Unknown Simultaneousoutbreakofmeasles


Congo(Etoumbi,Mbomo)

9/11 81.9 Unknown

2007 Marburgvirus Uganda(KamwengeDistrict)

2/3 66.6 Unknown OriginsthoughttobeinLeadandGoldminesofarea


DemocraticRepublicofCongoKasaiOccidentalprovince

187/264 70.8 Unknown

2007-2008

Bundibugyoebolavirus

Uganda(BundibugyoDistrict)

25/149 16.8 Unknown 1strecordedoccurrenceofnewstrain

2008 Marburgvirus NetherlandsexUganda(MaramagamboForest)

1/1 100 CaveinMaramagambobats?

40yearoldDutchwomen,visitedcaveinNationalPark

2008 Ebola-Reston

Phillipines 6assymptomticcases

0 Pigs 1stknowndetectionofEbola-Restoninpigs.6assymptomticcasesamongstslaughterhouseworkers.


of 23


2008-2009

Zaireebolavirus

DemocraticRepublicofCongo

15/32 47 OutbreakinMweka&LueboofKasaiDistrict


Germany 0/1 0 Laboratoryinfection

Animalvaccinestudies

In1976,asevereandoftenfatalviralhaemorrhagicfeveroccurredinsimultaneousoutbreaksintheequatorialprovincesofsouthernSudanandnorthernZaire(Table31.2).Amongsttheseveralhundredcasesofinfectionidentified,fatalityratesofabout90and60%respectivelyoccurred.Severalgenerationsofhuman-to-humanspreadcontributedtotheseverityoftheoutbreak.ThetwovirusstrainsisolatedfrompatientsinSudanandZairewherefoundtobemorphologicallyidenticaltoMarburgbutantigenicallyandbiologicallydistinct(Bowenetal.1977;WHO1978a,b).TheviruswasnamedEbolaafterariverinZaire.

Numerousfollow-upecologicalstudieshavefailedtodiscoverthereservoir.DuringstudiesoftheSudaneseepidemicin1976,anon-fatalEbolainfectionoccurredwithintheUKin1977afteralaboratoryaccident(Emondetal.1977).Justover6monthsaftertheoriginaloutbreaksinZaire,a9yearoldgirldiedofacutehaemorrhagicfeverinTandala,northernZaire(Heymannetal.1980).AfurthersmallepidemicoccurredinthesameregionofSudanin1979when22(65%)of34infectionswerefatal,withtransmissibilitybeingassociatedwithperson-to-personspread(Baronetal.1983).ThegeographicareawidenedwhenaSwisszoologistbecameinfectedwhileundertakinganautopsyofadeadchimpanzeeinwesternCôted’Ivoireinlate1994.Thisresultedinhercontractinganon-fatalsevereEbolaillness(LeGuennoetal.1995).OnlyafterhertreatmentanddischargefromahospitalinSwitzerlandwasitdiscoveredthatshehadsufferedfromanEbolainfection.Alarger-scaleoutbreakinKikwit,BandunduProvince,Zaire1995demonstratedtoaworldwideaudienceaseverehemorrhagicillnessinvolvingsome316cases,ofwhich244died,givingamortalityrateof77%(WHO1995a).Athirdofthecasesinvolvedhealthcareworkers.TheKikwitoutbreakwassimilartotheoriginalepisodethatoccurredin1976,1000kmtothenorth.Asinpreviousoutbreaks,secondarycasesoccurredthroughclosepersonnelcontactwithinfectiousbodyfluids.Theuncontrolledspreadofinfectionresultedfromalackofmodernmedicalfacilitiesandsuppliesthatcouldprotectmedicalpersonnelfromthosepatientsinitiallyaffected.UnlikepreviousEbolaoutbreaks,concerncenteredonthepotentialforcommunity-widespreadfromKikwit,alargeanddenselypopulatedarea,tothelargercitesofKinshasaandBrazzavillecloseby.Controloftheoutbreakcoincidedwiththeintroductionofprotectiveequipmentandbarriernursingtechniques(WHO1995b).TherecognitionofEbolahasrecentlyextendedtoaconfirmedcaseintheCôted’IvoireofarefugeefromneighbouringLiberiainlate1995;othercaseswerereportedtoexistinhishomevillageinLiberia(WHO1995c).

During1996–1997,twosmalloutbreaksoccurredinGabon.ThesewerefoundintheforestregionsofMayiboutandBoouéareasandwhereassociatedwithpeoplehuntingandbutcheryofchimpanzees(Georges1999).Amajoroutbreakinvolving425casesoccurringforthefirsttimeinUgandaduring2000–2001.StudiesindicatedthatthethreemostimportriskfactorsassociatedwithitsspreadwereassociatedwithattendanceatfuneralsofEbolafevercases,havingdirectcontactwithcasesandprovisionofmedicalcarewithoutadequatepersonalprotectivemeasuresbeingused.Thegeographicalspreadcontinuedduring2001–3whenEbolaoutbreakswithcasemortalityratesreachingover80%wasrecordedinGabonandforthefirsttimeinTheDemocraticRepublicofCongo(DRC)(Okware2002;WHO2003;Formenty2003;WHO2004).RepeatoutbreaksintheDRCin2007andinUgandain2007–08producedcasefatalityratesof70%and25%respectively.

Unexpectedly,EbolavirushasalsoappearedoutsideAfricawhenidentifiedamongstcynomologusmonkeys(Macacafasicularis)importedintotheUSAin1989(Jahrlingetal.1990)andSiena,Italyin1992(WHO1992).Shipmentsofwild-caughtcynomolgusmonkeysoriginatedfromthesamehandlingfacilityinthePhilippines,wherethepresenceoftheviruswasdocumented.AlthoughatrulyAsianoriginforthesevirusstrainsisnotdiscounted,preliminaryserologicalandsequencingstudies,suggestaclosesimilaritywithisolatesfromthe1976Africanoutbreaks.

Theagent

Taxonomy

EbolaandMarburgaremembersofthefamilyFiloviridae(Kileyetal.1982;Pringle1991),namedfortheirfilamentousappearanceundertheelectronmicroscope(Fig.31.1a).SimilaritiesofgenomestructureandcomparablemechanismsofgeneexpressionsuggestthatthefiloviruseshaveanevolutionaryoriginincommonwiththefamiliesParamyxoviridae(whichincludemeaslesandmumps)andRhabdoviridae(whichincludesrabies)(Sanchezetal.1992).Thesethreevirusfamiliesaregroupedintoataxonomicorder(Table31.1),theMononegavirales(BishopandPringle1995).


of 23


ProgressivecharacterizationofthefilovirusesrevealedsubstantialdifferencesbetweentheMarburgvirusesandEbolaviruses(Richman1983)leadingtotheestablishmentoftwogenera,MarburgvirusandEbolavirus,withinthefamilyFiloviridae(Feldmann1994).ThegenusMarburgviruscontainsonlyonespecies,LakeVictoriaMarburgvirus,representedbyasinglevirus,LakeVictoriaMarburgvirus(MARV).ThegenusEbolaviruscurrentlycontainsfivespecies:Côted’Ivoireebolavirus(Côted’Ivoireebolavirus,CIEBOV),Restonebolavirus(Restonebolavirus,REBOV),Sudanebolavirus(Sudanebolavirus,SEBOV),‘Ugandaebolavirus’(‘Ugandaebolavirus,’‘UEBOV’),andZaireebolavirus(Zaireebolavirus,ZEBOV)(Feldmann2005;Mason2008)(Table31.3).Incomparison,thegenomesofmembersofthefiveebolaviralspeciesdiffergeneticallyby37–41%atthenucleotidelevel,andallofthemdifferfromMARVgenomesby>65%.AmongstthegenusEbolavirusthethreedistinctspecies,Bundibugyo,SudanandZairespecieshavebeenassociatedwithlargeoutbreaksofEbolahaemorrhagicfever(EHF)inAfricacausingdeathin25–90%ofallclinicalcases,whileCôted’IvoireandRestonhavenot.

Table31.3Filovirustaxonomy

Order Family Genus Species Abbreviation

Mononegavirales Filoviridae EbolavirusMarburgvirus

SudanebolavirusZaireebolavirusCoted’IvoireebolavirusRestonebolavirusBundibugyoebolavirusLakeVictoriamarburgvirus

SEBOVZEBOVCIEBOVREBOVBUBOVMARV

Molecularbiology

Filoviralgenomesconsistsofasinglenon-segmentednegative-strandedRNAabout19kilobasesinlengthandcontainsevengenesarrangedlinearlyandthatmaybeseparatedbyintergenicregions.Thelineararrangementofgenesfollowsasequencebeginningwitha3′non-codinguntranslatedregion,thecoreproteingenes,envelopegenes,andthepolymerasegeneattachedtotheuntranslatedregionatthe5′end.(Feldmannetal.1993;Sanchezetal.1993).Non-structuralproteinsarenotpresent.EachgeneisflankedbyhighlyconservedtranscriptionandterminationsitesthatdifferamongthedifferentFiloviruses(Weik2002).

ThegeneticsequenceofMarburgvirus(MBG)andtheavailablepartialsequenceofEbolavirus(EBO)indicatethatinbothcasessevenstructuralproteinsareencoded,whichareexpressedthroughtranscriptionofmonocistronicmRNAspecies.Thefirst(3’)geneofthefiloviralgenomes,NPamajornucleoprotein(NP;M 94–104).ThenucleocapsidiscomposedofRNA,L,NP,VP35,andVP30.AnalysisoftheNPgeneshowsashortputativeleadersequenceattheextreme3endfollowedbythecompletenucleoproteingene.Thetranscriptionalstart(3′…UUCUUCUUAUAAUU…)andtermination(3′…UAAUUCUUUUU)signalsoftheMBGNPgeneareverysimilartothoseseenwithEBOvirus.ThefiloviralVP35geneislocatedimmediatelydownstreamoftheNPgene.TheVP35proteinisthoughttobeatranscriptase–polymerasecomponentthatisconsideredtobetheP(NS)proteinequivalentofparamyxo-andrhabdovirusesTheVP35andVP35-NPcomplexesalsoinhibitbothdsRNA-mediatedandvirus-mediatedinductionofinterferon-responsivepromotersandconsequentlythecellularinterferoninnateimmuneresponsetovirusinfection.Thefiloviralmatrixormembrane-associatedVP40geneislocateddownstreamoftheVP35geneandisthemostconservedofallfilovirusgenes,itencodesthematrixproteinVP40protein(M 32000).ThefiloviralGPgeneisasinglesurfaceglycoprotein(GP;M 170000).MarburgandebolavirusencodeoneandthreeglycoproteinsfromtheirGPgenes,respectivelyThefiloviralminornucleoproteinVP30gene(VP30;M 32000),locateddownstreamoftheGPgene,isanotheruniquecomponentofthefiloviralgenomes.Itencodesaprotein,VP30.TheN-terminusofVP30bindsdirectlytosingle-strandedRNA,andprefersfiloviralRNAoverunspecificRNA(John2007)VP30isalsoazinc-bindingprotein.Intheabsenceofzinc,filovirus-genometranscriptionisabolished(Modrof2003)).TheVP24geneanditsexpressionproductisasecondmatrixormembrane-associatedVP24protein(M 24000).RecentexperimentsalsoindicatethatVP24counteractstheinterferon-responseofvirus-infectedcells(Reid2007).Thelast(5’)geneofthefiloviralgenomeistheLgene,whichencodesthecatalyticpart(Lprotein;MARV:2,331amino-acidresidues,267kD;ZEBOV:2,212amino-acidresidues,253kD)oftheviralRNA-dependentRNApolymeraseholoenzyme,(M 267000);whichalsocontainsVP35(27,195,283).

Incomparisontoothernon-structuralnon-segmentednegative-strand(NNS)RNAviruses,filovirustranscriptionalsignalsareverysimilartothoseofmembersoftheparamyxovirusandmorbillivirusgenera.Nucleotidesequenceanalysisofthe3’end,includingtheentireNPandLproteinencodinggenesoftheMBGandEBOgenome,hasshownsimilarstructureandorganizationwithotherNNSRNAviruses.ThesimilarityofthefilovirusNPgenesandgeneproductstothoseoftheparamyxovirusesimplyacloserbiologicalandphylogeneticrelationshiptotheseagentsthantorhabdoviruses.

r

r r

r

r

r


of 23


Growthandsurvival

Filovirusesundergorapid,lyticreplicationinthecytoplasmofawiderangeofhostcells.ThemodeofentryofFilovirusesintocellsoccursbybindingtounidentifiedcell-surfacereceptorswiththeirspikeproteins.Althoughsomeultrastructuralstudieshavesuggestedthatvirionsareassociatedwithentrybyendocytosis.Africangreenmonkeykidneycells,suchasCV-1andVeroderivatives,arecommonlyusedtogrowfilovirusestohightitres.Thefiloviralnucleocapsidisreleasedintothecytosolsubsequenttofusionoftheviralandcellularmembrane,andcompleteuncoatingofthefilovirusgenometakesplace.ThepolymeraseholoenzymeL/VP35,broughtintothecellwiththenucleocapsid,transcribesthefilovirusgenesinasequence,synethizingtheantigenomethatisusedasthetemplatetosynthesizetheprogenygenes.ThefiloviralmessengerRNA’sareabundantininfectedcellsandaretranslatedintothefiloviralstructuralproteins.TheNP,VP30,VP35andLproteinsassemblewiththenewlysynthesizedgenomestoformRNPscomplexes.TheserecruitthematrixproteinsVP40andVP24andbudfromthecell’splasmamembrane,acquiringtheGPenvelopewithitssurfaceprojectionsbybuddingfromthecellmembranes(Noda2006).Theentirelifecycleoccursinthecytoplasmofthehostcell.Nucleocapsidsalsoaccumulateinthecytoplasm,formingprominentinclusionbodies.

Laboratoryinfectionoftissuecellsshowsintracytoplasmicvesiculationandmitochondrialswellingfollowedbyabreakdownoforganellesandterminalrarificationandcondensation.Thesecytoplasmicchangesoccursimultaneouslywiththeaccumulationofviralnucleocapsidmaterialinintracytoplasmicinclusionbodiesandthelargenumbersofvirionsextracellularly(Fig.31.1b).

Thefilovirusvirionisbacilliforminstructureandiscomposedofahelicalnucleocapsid,consistingofacentralaxis(20–30nmindiameter),surroundedbyahelicalcapsid(40–50nmindiameter).Ahostcellmembranederivedlipidouterenvelope,withregular10nmprojectionssurroundsthenucleocapsidandcompletesthestrikingandcharacteristicappearanceundertheelectronmicroscope(Fig.31.1a).Althoughthereareoftenstructuresofvaryinglength,withloops,branches,andotherirregularities,evidenceexiststhatinfectiousparticlesconsistmainlyofsimplelinearformsabout1μminlength.

MarburgandEbolavirusinfectivityarestabilizedatambienttemperature(18–20°C)butinactivatedwithin30minat60°C.Ultravioletandgammairradiation,lipids,solvents,β-propiolactone,hypochlorite,andphenolicdisinfectantsalldestroyinfectivity.

Diseasemechanisms

Theexactmechanismbywhichfilovirusescausesuchaseriousillnessisbeingunravelled.Thereisextensiveviralreplicationinliver,lymphoidorgans,andkidneys.Extensivevisceraleffusions,pulmonaryinterstitialoedema,andrenaltubulardysfunctionoccurringafterendothelialdamageleadingtohypovolaemicshockareallobservationscontributingtodeath.Severe,acutefluidlossaccompaniedbybleedingintothetissueandgastrointestinaltractischaracteristicandleadstodehydration,electrolyteandacid-baseimbalance.Inprimatesandclinicalcasesstudiedearly,lymphopeniaisfollowedbyamarkedneutropenia(Fisher-Hochetal.1983).Inthelaterstagesoftheinfection,andinassociationwiththethrombocytopenia,theremainingplateletsareunabletoaggregateinresponsetoADPorcollagen.Ithasbeensuggestedthatthedysfunctionofplateletsandendotheliaextendstootherelementsoftheendothelialsystem,suchasmacrophages(Fisher-Hochetal.1985).InexperimentalmonkeyEbolainfections,virushasbeenidentifiedinvascularendothelialcells.HumansconvalescentfromMarburgandEbolainfectionshavehadvirusisolatedupto3–4monthsafteronsetinsemen,inapatientwithuveitis,anteriorchamberfluid.Thereisnoevidenceoflong-termpersistence,latencyorlatedegenerativediseaseinthesmallnumberofpatientsobservedorinmonkeysrecoveringfromthedisease(Fisher-Hochetal.1992a).

Thehosts

Human

Incubationperiod

Filovirusesaretransmittedthroughdirectcontact.Theyenterthroughsmallskinlesionsorthroughdamagedmucousmembranesandinitiallyinfecttargetcellssuchasmacrophages,whichtransportthemthroughthebody.TheincubationperiodforMarburgvirusdiseaseis3–9days(Martini1971;Bausch,2006)andforEbolavirusabout10days(Bwaka1999)5–7daysforneedletransmission(Emond1978)and6–12daysforperson-to-personspread.

Symptomsandsigns

TheillnessescausedbyMarburgandEbolavirusesarevirtuallyindistinguishable.Followingexposureandincubationperiod,bothinfectionshaveanabruptonsetofillnesswithinitialnon-specificsymptomssuchasfever,severefrontalheadache,backpainmalaise,andmyalgia.Earlysignsincludetachycardia,conjunctivitis,andmaculopapularrashes,


of 23


whichdevelopafter5–7daysonface,buttocks,trunkorarmsandlatergeneralizesovertheentirebodywithdesquamationinsurvivors.Withinaweekto10days,thosedestinedforrecoverybegintoimprove,eventhoughrecoveryfromtheseveredebilitatingeffectsofthediseaseoftentakesweeks.AlargenumberofpatientsinbothMarburgandEbolaoutbreaksdevelopseverebleedingbetweenthefifthandseventhdays.Patientswithsevereinfectionsoftenexperiencepharyngitis,severenausea,andvomiting,progressingtohaematemesisandmelena.Petechiae,ecchymoses,uncontrolledbleedingfromvenepuncturesitesandpost-mortemevidenceofvisceralhaemorrhagiceffusionsarecharacteristicofsevereillness(Smithetal.1978).Deathusuallyoccursbetweenthe7–10days(range1–21days)afteronsetofclinicaldiseaseandisprecededbyseverebloodlossandshock.Convalescenceisslowandmarkedbyprostration,weightloss,andamnesiaforaconsiderableperiodaftertheacuteillness(Piot1978;Formenty1999).Deathoccursusuallyafter8–16daysofinfectionduetoshockaftermulti-organfailure,oftenbroughtonbysecondarybacterialinfections.

Clinicallaboratoryfindingsincludeearlyleucopoeniawithleftshiftofthegranulocytesaccompaniedby,markedthrombocytopenia,andabnormalplateletaggregation.Serumaspartateaminotransferase(AST)/alanineaminotransferase(ALT)enzymelevelsareraisedandcharacterizedbyahighAST/ALTratio(10–3:1)andγ-glutamyltranspeptidaseindicatingliverdamage.Otherfindingsincluderaisedlevelsofcreatineandurealevelspriortorenalfailureandhypokalemiabecauseofthediarrheaandvomiting.

Asthedifferentialdiagnosisintheearlyacutephaseisdifficult,othercausesneedconsideration.Themostcommoncausesofimportedinfectionsshowingasevere,acutefebrilediseasearemalariaandtyphoidfever.Therefore,delayindifferentialdiagnosisandtreatmentneedstobeminimized.Alternativecausesincludebacterialdiseasessuchasmeningococcalsepticaemia,Yersiniapestisinfection,leptospirosis,anthrax;rickettisaldiseasessuchastyphusandmurinetyphus;andviraldiseasessuchassandflyfever,yellowfever,chikungunyafever,RiftValleyfever,hantavirus,andCongoCrimeanhaemorrhagicfever.

Diagnosis

ThediagnosisofEbolaorMarburgshouldbeconsideredinpatientsshowingacute,febrileillnesshavingvisitedknownepidemicorsuspectedendemicareasofruralsub-SaharanAfricaandAsia,particularlywhenhaemorrhagicsignsarepresent.Alltissues,blood,andserumcollectedintheacutestagesofillnesscontainlargeamountsofinfectiousvirus.Extremecareshouldbetakenwhendrawingorhandlingbloodspecimensasthevirusisstableforlongperiodsatroomtemperature(Elliottetal.1982).Allneedlesandsyringesneeddiscardingtopuncture-resistantcontainerswithlids,andincinerated.Specimensofbloodshouldbetakenwithoutanticoagulant.Bloodorserumshouldbetransferredtoaleakproofplasticcontaineranddoublewrappedinleakproofcontainersfortransportationtoahighcontainmentlaboratory.Transportationshouldbeunderappropriatebiocontainmentwithindryorweticeaccordingtointernationaltransportationornationalregulations(DepartmentofHealth2007;WHO2007)afterconsultationwithanyoftheglobalmaximumcontainmentreferencelaboratories.

Inactivationofpatientsserawithirradiationorheatingat60°Cfor30minrenderthemsafeforundertakingimmunoassaytests.Althoughmorphologicallysimilar,MarburgandEbolaareimmunologicallydistinct.Theimmunofluorescenceassay(IFA)hasbeenthebasicdiagnostictestforfilovirusinfectionandtheonlyonethathaswidespreadacceptanceforthediagnosisofhumanEboladisease(WulffandJohnson1979;Rollinetal.1990).ArisingantibodyinpairedserumorahighIgGtitre(>64)andpresenceofIgMantibody,togetherwithclinicalsymptomscompatiblewithahaemorrhagicfever,areconsistentwithadiagnosis.ThepresenceofMarburgantibodyisconsideredaspecificresultbutEbolaviruslow-titre,non-specific,false-positiveserologicalreactionsdooccur.WhenusingIFAtheproblemoflow-titrefalsepositivesmakesinterpretationdifficultwhenundertakingnon-humanprimateandhumanseroepidemiologicalsurveys.FortheIFA,theantigensubstrateconsistsofvirus-infectedVerocellsdriedontospotslides.RecentadvancesinmolecularbiologyhaveexpressedthenucleoproteingeneofEbolavirusinabaculovirusexpressionsystem.Thus,alargeamountofnon-infectiousproteinisapossiblesourceofantigenformanyserologicaltests(IFA,ELISA).Thereevaluationleadingtoanimprovementinthedetectioncapabilitywithinseroepidemiologicalfieldstudiesandinthescreeningofimportedprimates.

Filovirusescanbeeasilyisolatedfrominoculationoffreshorstored(−70°C)specimensofbloodorserumcollectedduringtheacutephaseofillnessintoVeromonkeykidneytissueculturescellsusinglaboratorycontainmentlevel4facilities.Verocells(particularlycloneE6)andMA-104haveprovedtobethemostsensitiveandusefulcellsforthepropagationandassayoffreshisolatesandlaboratorypassagefilovirusstrains.Primaryisolationusingtissueculturerarelyproducesaspecificcytoplasmiceffect,thusevidenceofinfectionisbasedontheappearanceofcytoplasmicinclusionbodiesdemonstrated2–5daysafterinoculation,byimmunofluoresencestaining,usingantipolyclonalanti-seraorvirussubtypeorstrain-specificmonoclonalantibodies.SomefilovirusstrainssuchasEbolaSudanaredifficulttogrowinprimaryculturesandsuccessisimprovedthroughtheintraperitonealinoculationofyoungguineapigs.Amonitoredfebrileresponsecoincideswithhighlevelsofvirusintheblood,whichcanberecoveredintissuecultureorexamineddirectlybytheelectronmicroscope.IneachoftheFiloviridaeoutbreakselectronmicroscopyhasprovenusefulintheidentificationofMarburgorEbolainbodyfluidsandtissue,andcellculturesupernatants.DuringtheRestonepizootic,


of 23


immunoelectronmicroscopy,whenusedinconjunctionwithstandardtransmissionmicroscopy(TEM)ofinfectedcells,providedconsistentresults(GeisbertandJahrling1990).However,thetechniquewillnotdistinguishbetweentheFiloviridaestrains.Virusmayalsobedetectedinarangeofspecimens,includingthroatwashings,semenandanterioreyefluid.Thepresence,ofEbolaandMarburgintissuesofmonkeys,bothexperimentallyandduringprimateoutbreaks,hasbeendemonstratedbyelectronmicroscopy(Baskervilleetal.1985;GeisbertandJahrling1990);anddetectionofhightitresinthebloodofinfectedpatientsandmonkeysindicatedtheusefulnessofanantigencaptureELISAsystem(Ksiazeketal.1992).SuchasystemhasbeenofconsiderableuseintherecentKikwitepidemic.ImmunobilizedmousemonoclonalantibodiesonasolidplasticsurfacecaptureEbolaantigencontainedintissueorbloodspecimens.Rabbitpolyclonalanti-filovirusserumdetectstheantigen.Theantigenimmunoabsorbentdetectionassayhasprovedarapidandreliableprocedurefortheearlydetectionoffilovirusinfectionsandwouldproveusefulasamethodfortheroutinescreeningofimportedprimates.

Inrecentyears,theuseofcross-reactingandstrain-specificprobesforthereversetranscriptasepolymerasechainreactionRT-PCRhasevolvedtothegoldstandardforFilovirusdiagnosisinthefieldandhastakentheplaceofpreviouslywidelyusedIFAsandELISAs.ConfirmatorydiagnosisofRT-PCR-positivesamplesisusuallyperformedbyvirusisolationinmaximum-containmentfacilities(Grollaetal.2005;Towneretal.2004).

CurrentlyalloutbreaksofEHFandMHF,infectionsareconfirmedbyvariouslaboratorydiagnosticmethods.Theseincludevirusisolation,reversetranscription-PCR(RT-PCR),includingreal-timequantitativeRT-PCR,antigen-captureenzyme-linkedimmunosorbentassay(ELISA),antigendetectionbyimmunostaining,andIgG-andIgM-ELISAusingauthenticvirusantigens(Gibbetal.2001;Ksiazeketal.1992,1999;Leroyetal.2000;Towneretal.2004;Zakietal.1999;Saijoetal.2006).

Primates

AfricangreenmonkeysimportedfromUgandaweretheidentifiedsourceoftheMarburgoutbreak(Hendersonetal.1971),andcynomolgusmonkeysthesourceebolarestonvirus.Bothspecieswereimportedandcloselyassociatedwithmedicalresearch.

Thegeneralcharacteristicsofprimatefilovirusinfectionsamongstexperimentallyandnaturallyinfectedprimatessuggestthattheincubationperiodvariesbetween4and20days,duringwhichtimethevirusreplicatestohightitreintheliver,spleen,lymphnodes,andlungs.Theclinicopathologicalfeaturesnotedincludehighfever,severeweightloss,anorexia,haemorrhages,andadistinctiveskinrashinassociationwithsplenomegaly,markedelevationoflactatedehydrogenase,alanineaminotransferaseandaspartateaminotransferase.TheASTlevelsareconstantly2–10timeshigherthanthatofALT.Evidenceofthrombocytopeniaisapronouncedfeaturebutanaemiaisnot.Bothlymphocytopeniaandleucocytosisareevidentanddependentonthestageoftheinfection(Fisher-Hochetal.1983).Severeprostrationwithdiarrhoeaandbleedingleadstorapiddeathinalmostallanimals.Theseverityofthediseaseinprimatesdependsonthefilovirusinfectionandhostinvolved.AfricangreenmonkeysarefarlesssusceptibletosevereorfataldiseaseduetoEbolavirus(Sudan)orEbola(Reston)thancynomolgusmonkeys.However,AfricangreenmonkeysexperimentallyinfectedwithMarburgvirusafterthe1967outbreakalldiedirrespectiveofrouteofinfection(HassandMass1971).Marburgvirusinfectionofrhesusmonkeysislesssevereorfatal,similartoEbola(Sudan)infection.InfectionbyEbolavirus(Zaire)isuniformlyfatalinallspeciessofarchallenged,regardlessofinoculum.

Histopathologicalfindingsincludeseverehepatocellularnecrosis,necrosisofthezonaglomerulosaoftheadrenalcortex,andinterstitialpneumonia,allassociatedwiththepresenceofintracytoplasmicamphophilicinclusionbodies.Thenecroticlesionsresultfromdirectvirusinfectionoftheparenchymalcells.Littleinflammatoryresponseoccursatthesiteofthelesions.

Experimentalpathophysiologicalstudieshavedemonstratedendothelialcellandplateletdysfunctionaccompaniedbyoedema,multipleeffusions,haemorrhage,andhypovolaemicshock(Fisher-Hochetal.1985).RecentstudiesinMacacafascicularisandCercopithecusaethiopssuggestthattherecentlyisolatedAsianfilovirusesarelesspathogenicforprimatesthantheAfricanfiloviruses(Fisher-Hochetal.1992b).

Treatmentandprognosis

Thereisnolicensedvaccineoreffectiveantiviraldrugtreatmentlicensedforuseinhuman.TherapyforMarburgandEbolavirusinfectionislimitedtotheprovisionofsupportivemeasuresandgeneralnursingcare.Inthedevelopmentofvaccines,recentadvanceshaveshownprotectioninanimalmodels.Amongstthemostrecentpromisingvaccinesunderdevelopmentareanumberofrecombinantbasedsystems.Themostnoticeablethosebasedvesicularstomatitisvirus(VSV)thatexpressesasinglefilovirusglycoprotein(GP)inplaceoftheVSVglycoprotein.Asingledosevaccinehasprovedcapableofprotectingnon-humanprimatesagainstSudanebolavirus(SEBOV),Zaireebolavirus(ZEBOV),Coted’Ivoireebolavirus(CIEBOV),andMarburgvirus(MARV)(FeldmannHetal.2007;Geisbertetal.2009).Recently,atwo-


of 23


injectionfilovirusvaccineregimebasedonanadenovirusvectorexpressingmultipleantigensfromfivedifferentfiloviruses,(ZEBOVNP,ZEBOVGP,SEBOVGP,MARVCi67strainGP,MARVRavnstrainGP,MARVMusokestrainNP,MARVMusokestrainGP),provedsuccessful(Prattetal.2010).Allanimalsinthesestudiessurvivedtheinitialfiloviruschallengewithadifferentstrainorspeciesoffilovirus.However,thereareanumberofsignificantsafetychallengesinhumans;particularlythosewithanalteredimmunestatusareyettobeovercome.

Intensivesupportivecareiscurrentlyconsideredmostimportant:preventionofshock,cerebraloedema,renalfailure,bacterialsuperinfection,hypoxia,andhypotensionmaybelifesaving.Patientcareiscomplicatedbytheneedforisolationandprotectionofmedicalandnursingpersonnel.Theuseofplasticpatientisolatorsisarequirementinmanycountries,includingtheUKandEurope,despitethereturntothestrictbarriernursingtechniquesnowfavouredintheUSAandintherecentAfricanoutbreaksinZaire,Côted’Ivoire,Gabon,UgandaandAngola.

Epidemiology

Epidemics

Marburgvirusdisease

AfulminatinghaemorrhagicfevercausedbytheMarburgviruswasfirstrecognizedinAugust1967whenitaffectedlaboratoryworkersinthreesimultaneousoutbreaksinMarburgandFrankfurt,Germany,andBelgrade,formerYugoslavia(Martini1969).Altogether,therewere31humaninfections,ofwhom25hadprimaryinfectionsacquiredthroughcontactofbloodandtissuesfromshipmentsofAfricangreenmonkeys(Cercopithecusaethiops)importedfromUganda,viaLondon.Thelargestnumberofprimaryinfections(20)occurredamongworkersofaMarburgpharmaceuticalfirmwhopreparedkidneycellsforvaccineproduction.Amongthoseinfected,exposurewasattributedtoautopsies(13),cleaningofcontaminatedglassware(5),dissectionofkidneys(1),andlaboratoryaccidentinvolvingcontaminatedbrokenglassware(1).Personnelnotindirectcontactwithcontaminatedmaterialorwhoworeprotectiveglovesormasksforworkwithmonkeyswasnotinfected.InFrankfurt,fourfurtherprimaryinfectionsoccurredinworkersexposedtotissueculture.Aveterinaryofficercarryingoutroutinepost-mortemswasthesinglerecordedprimarycaseinBelgrade.Fourofthesecondaryinfectionsoccurredinhospitalpersonnelwhocameintoclosecontactwithpatients.Thefifthwasthewifeoftheveterinarysurgeon,whofellill10daysafternursingherhusbandathome.Thesixthcaseinvolvedthewifeofapatientwhohadtransmittedthediseasethroughsexualintercourse83daysaftertheillness.Sevenoftheprimarycaseswerefatal,butnofatalitiesoccurredamongstthesixsecondarycases.

Around600animalsoriginatingfromfourshipmentsreachedEuropefromUgandaovera3-weekperiod.Frankfurtreceived50–60animalsfromtwoshipments,Belgradeapproximately300animalsfromthreeshipments,andtheremainderwenttoMarburg.Allspentbetween60and87daysinaholdingfacilityinUgandabeforebeingshippedtoLondon,Heathrowwheretheyspent636hoursintheanimalhostelbeforebeingforwardedtoGermany.DetailsontheBelgradeenzooticindicatedthat46of99animalsimportedfromthefirstshipmentdied,and20and30fromthesecondandthirdshipments,respectively.Thisepizooticwascharacterizedbydailydeathsofoneormoreanimalsthroughoutthe6-weekquarantineperiod,suggestingongoingtransmissionbetweenanimals.Epidemiologicalevidenceoftheoutbreaksuggestedthattransmissionbetweenmonkeysinquarantinefacilitieswasthroughdirectcontactwithcontaminatedequipment.Directcontactwithinfectedbloodandtissuewasconsideredthesourceforallhumancases,andtherewasevidenceofaerosoltransmission.NoepizooticswerefoundinUgandaalthoughuncorroboratedinformationhadsuggestedalargenumberofmonkeydeathsincoloniesontheislandnearLakeKyoga,northofLakeVictoria,totheeastofMountElgoninKenya.Ugandanmonkeyswerecapturedinthisarea,transportedtoEntebbe,wheretheywereheldfor3dayspriortoshipment.

ThefirstrecognizedoutbreakofMarburgvirusdiseaseinAfrica,andthefirstsincethe1967outbreak,occurredinSouthAfricainFebruary1975(Gearetal.1975)(Fig.31.2b).TheindexcaseinvolvedayoungAustraliantouristwhohadhitchhikedthroughZimbabweanddiedafteradmissiontoaJohannesburghospital.Shortlyafterwardstwonon-fatalsecondarycasesoccurred,onehisfemaletravellingcompanionandanurse(Table31.1).Again,therewasevidencethattheviruspersistedinthebody;theviruswasrecoveredfromfluidaspiratedfromtheanteriorchamberofthenurse’srighteye80daysafteronsetofillness.InJanuary1980,Marburgre-appearedinKenya(Smithetal.1982).TheindexpatientwasanelectricalengineerwhoacquiredthefatalinfectioninwesternKenya.Anon-fatalsecondaryinfectionoccurred9dayslater.Thisinvolvedadoctorwhoattendedthepatientandhadattemptedmouth-to-mouthresuscitation.In1987,anisolatedcaseoffatalMarburgdiseasewasagainrecognizedina15yearoldDanishboywhohadbeenadmittedtohospitalinKenya.Ninedayspriortotheonsetofhisdisease,healsohadvisitedKitumCaveinMountElgonnationalpark.RecentstudiesofcoloniesofR.gypriacusbatswhichinhabitthesecaveshavedemonstratedmolecularandserologicallypositiveforMarburgvirusbutthereroleintransmissionisasyetundefined(Kuzminetal.2010).PresentlyitisthoughtthatthehabitatofthenaturalhostofMarburgvirusiswithin,butnotlimitedto,theMountElgonareaandpossiblyoverlapsthedistributionofEbola.


of 23


Fig.31.2DistributionanddatesoffilovirusoutbreaksinAfrica(a)Ebolavirusdiseaseand(b)Marburgvirusdisease.

Between1987and1998,theonlycaseofMarbugreportedwereassociatedwithlaboratoryaccidentsintheformerSovietUnionofwhichonewasfatal(Nikiforovetal.1994)outlinesthedangersassociatedwithworkingwiththeseagentsinthelaboratory.

However,in1998,thelargestnaturaloutbreakofMarburgvirusdiseasetodatebeganinnortheasternDemocraticRepublicoftheCongo(DRC).Thistime,thefocusoftheoutbreakwasatowncalledDurba(population16 000).AlargenumberofmeninthisregionworkfortheKiloMotoMiningCompany,whichrunsanumberofillegalgoldminesinthearea.TheMarburgoutbreakstartedinNovemberof1998,althoughnotreportedtoanyinternationalagenciesuntillateAprilof1999,followingthedeathofthechiefmedicalofficerintheareafromthedisease.Theoutbreakhadacasefatalityrateofapproximately83involving154casesbeforethedeclarationthattheoutbreakwasoverin2000.ThediseasealsospreadtoneighbouringvillagesparticularlyWatsa.MinershadasignificantlyhigherriskofcontractingMarburgthanthegeneralpopulationofthisarea,suggestingfrequentexposuretothenaturalreservoirofMarburgvirus(Bausch2006).

Thesizeandextentofthisoutbreakwaseclipsedatthebeginningin2004,whenaMarburgoutbreakoccurredinAngoladuringOctober.Duetocivilwarinthecountryandanon-existentpublichealthinfrastructure,recognitionoftheoutbreakwasdelayeduntilalmost6monthslater,inMarchof2005.TheoutbreakwasdeclaredoverinNovemberof2005,afternoadditionalcaseshadbeenreported(Towner2006).

In2007threecasesinyoungmales,againassociatedwithminersworkinginLeadandGoldminesintheKamwengeDistrictofUgandawasreported(WHO2007).Finallyin2008,aDutchtouristdevelopedMarburgfourdaysafterreturningtotheNetherlandsfromathreeweekholidayinUganda.Todate,thesourceoftheexposurehasnotbeenconfirmed,althoughthewomanvisitedPythonCaveinwesternUgandawherebatswerepresent(WHO2008,2009;Timenetal.2009).TheUgandanMinistryofHealthclosedthecaveafterthiscase.

Ebolavirusdisease(Africa)

Twolargesimultaneousoutbreaksofanacutehaemorrhagicfever(subsequentlynamedEbolahaemorrhagicfever)occurredinsouthernSudan(WHO1978a)andnorthernZairein1976(WHO1978b)(Fig.31.2b).ThefirstoutbreakwasidentifiedinsouthernSudaninJune,continuingthroughtoNovember1976.Therewere284cases,67inNazara,213inMaridi,3inTembura,and1inJuba.ThefocusoftheepidemicwasNazara,asmalltownwithclustersofhousesscatteredindensewoodlandborderingtheAfricanrain-forestzone.TheoutbreakinNazaraoriginatedinthreeemployeesofacottonfactorysituatednearthetowncentre.Detailedfactoryrecordsfortheprevious2yearsdidnotshowanyfatalhaemorrhagicdiseaseinNazarauntilJune1976.Atthattime,oneortwoworkersstarteddyingeachweek.BySeptember,6factoryworkersand25oftheircontactshaddevelopedthesameillness,ofwhich21died.Beforetheoutbreakdiedoutspontaneouslycaseswerereportedintwoneighbouringareas.ThefirstwasinTembura,asmalltown160kmnorthofNazara,whereanillwomanwenttobenursedbyherfamily.Beforeshedied,threewomenwhocaredforheralsodiedofthesamehaemorrhagicdisease.Noothercaseswerediscovered.Secondly,theepidemicwasdramaticallyamplifiedbythelargerhospital-associatedoutbreak(213cases)inMaridi,followingtheintroductionofapatientfromNazara.Maridi,atowneastofNazara,hadanestimatedpopulationof10,000people.Ninety-threecases(46%)acquiredtheirdiseaseinhospital,and105(52%)inthecommunity.Ofthe230staffatMaridihospital,72becameinfectedwhileatworkand41


of 23


died.Thehighestrateofinfectionwasassociatedwithnursinghaemorrhagicpatientswho,attheheightoftheepidemic,occupiedmostwards.AfterMaridi,furthercases(onefromNazaraandthreefromMaridi)weretransferredtotheregionalhospitalinJuba.AfurtherthreepatientswereflowntoKhartoum(1,200kmnorth),wheretwodied.AnursefromJubawastheonlysecondarycaseidentifiedasaresultofthesepatienttransfers.

Overall,therewere151deaths(mortalityrate,53%)outof284cases.TheoutbreakinNazaracontinueduntilOctober,infecting67peopleofwhom31(46%)died,comparedto116(54%)inMaridi.Studieson36familieswhonursed38primarycasesindicatedthatof232contacts30(14%)developeddisease.Similarratesoftransmissionwereobservedinsubsequentgenerations,givinganoverallsecondaryattackrateof12%.BetweenJulyandOctober1979,34casesofEbolahaemorrhagicfeverrecurredintheYambio-NazaraDistrict.Fivefamilygroupsandtwoindividualsbecamecontractedtheillness.Theindexcase,acotton-factoryworker,transmittedthevirustoseveralmembersofhisfamily.Theoutbreakextendedtootherfamiliesthroughnosocomaltransmissionduringhishospitalizationandthehospitalizationofsubsequentcases.Mortalityinthisoutbreakwas65%(22deaths).Itwasunclearwhetherthecottonfactorywasthesourceoftheindexcaseofinfection.

AlsoduringSeptembertoOctober1976,alargeoutbreakofEbolahaemorrhagicfevertookplaceintheequatorialrainforestofnorthernZaire(WHO1978b).TheindexcasehadbeentouringandpresentedhimselftotheoutpatientclinicatYamkukaMissionHospital(YMH)fortreatmentofacutemalaria,andreceivedaninjectionofchloroquine.Hewasadmittedtohospital10dayslaterwithgastrointestinalbleedinganddied.Duringthefollowingweek,nineotherpatientswhohadreceivedtreatmentattheoutpatientclinicoftheYMHcontractedEbolahaemorrhagicfever.Almostallsubsequentcaseshadreceivedinjectionsorhadbeeninclosecontactwithotherpatients.Thehighestincidencewasamongstwomenof15–29years,whohadattendedantenatalandoutpatientclinicsatthishospitalandreturnedtotheirvillages.After13of17staffhadacquiredthediseaseand11patientsdied,thehospitalclosed.Themajorriskfactorprovedtobethere-useofnon-sterilizedneedles,whichwereinshortsupply.Between1Septemberand24October,therewere318knowncasesofEbolahaemorrhagicfeverwith280deaths,acasefatalityof88%.Therewereover55villagesintheendemicarea(Bumbazone),containingsome550recordedcases.Theoverallsecondaryattackratewascalculatedtobe5%,butnearer20%incloserelativesofacase.AfurthersinglefatalcasewasidentifiedinTandalaHospitalinnorthwesternZairein1977(Heymannetal.1980).StudiesintheTandalaregionrevealedtwopossibleEbolacasesdatingbackto1972,anda7%Ebolaseroprevalencerateinthelocalpopulation.

InJanuary1995,acharcoal-makernearKikwit,atowninBanduduProvince,550kmeastofKinshasa,wasthefirstfatalcaseofEbola(WHO1995a).ByearlyMarch12membersofhisfamilyhaddied.Simultaneously,aShigellaIdysenteryepidemicwastakingplaceandmaskedtheearlystagesoftheEbolaoutbreak.HospitalsbecamesourcesofinfectionduringFebruarywhenanEbolapatiententeredtheKikwithealthcentreandlatertransferredtothegeneralhospital.DuringApril,membersofaresuscitatingteambecameillafterhandlingapatientmisdiagnosedashavingtyphoid.Rapidtransmissionofunprotectedhealthworkersandotherpatientsoccurred,manycarryingthediseasebackintothecommunity.BetweenJanuaryandJune315caseshadoccurred,ofwhich244died(77%).Thefemale:maleratiowas166:149,which74%(123)femalesand81percent(121)malesdied.Provisionaldataidentified75(26%)nursesorstudentsand61(21%)housewiveswhocontractedthedisease.Twohundredandsixty-six(84%)ofthecasesresidedwithintheKikwitNorthandSouthZonesdeSanté.NocasesidentifiedoutsidetheBandunduregion.

ThegeographicdistributionofEbolaviruswidenedinNovember1994whenanon-fatalEbolahaemorrhagicfevercaseemergedforthefirsttimeinWestAfrica(LeGuennoetal.1995).IntheTaiNationalPark,Côted’Ivoire,a34yearoldethnologistinfectedherselfwhilecarryingoutapost-mortemonawildchimpanzeefounddeadwithsignsofhaemorrhages.Eightdayslater,shewasadmittedtohospitalinAbidjanforsuspectedmalaria.Astherewasnoimprovementinhercondition,shewasrepatriatedbySwissAirAmbulanceandadmittedtotheUniversityHospitalofBasel.Ashaemorrhagicfeverwasconsideredunlikely,shewastreatedwithciprofloxacinanddeoxycyclinforsuspectedGram-negativesepsis(typhoidfever),leptospirosis,orrickettsialdisease.RetrospectivestudiesisolatedtheEbolavirus.Noclinicalillnessnorseroconversionsweredetectedamong22contactpersonsintheCôted’Ivoireor52hospitalandair-ambulancestaffbasedinSwitzerland,despitethelackofanearlyEboladiagnosis.Latein1995,a25yearoldrefugeefromneighbouringLiberiawasadmittedtothehealthfacilityofGozon,Côted’Ivoire,confirmingthepresenceofEbolavirusinWestAfrica(CentersforDiseaseControl(CDC)1995c).Patientisolationandbarriernursingpreventedfurtherspreadofinfectionwithinandfromthehealthfacility.PreliminaryinvestigationofhishouseholdcontactsinthevillageofPlibo,MarylandCounty,LiberiafoundthattwomalecontactsshowedthesignsandsymptomsofearlyEbolainfection.

Zaireebolavirus(ZEBOV)hasrepeatedlycausedlargeoutbreaksinGabonbetween1994and2008(Geordes1999:WHO2003;Georges1998;Pourrut,2001),inDRCbetween2001and2005(Formenty2003)andintheDRCin1995and2007.In2007,103people(100adultsandthreechildren)wereinfectedbyasuspectedhemorrhagicfeveroutbreakinthevillageofKampungu,DRC.Theoutbreakstartedafterthefuneralsoftwovillagechiefs,and264peopleinfourvillagesfellill.TheCongo’slastmajorEbolaepidemickilled245peoplein1995inKikwit,about200milesfromthesourceoftheAugust2007outbreak(WHO2007).In2004,itresurfacedaroundGuluinUganda(Okware2002).Again,thediseasewasamplifiedinlocalhospitalsandspreadintoseveralUgandanadministrativedistricts.Therewereatleast425humancases


of 23


and224deaths(Bitekyerezo2002).On30November2007,theUgandaMinistryofHealthconfirmedanoutbreakofseveregastrointestinaldiseasecausedbyEbolaintheBundibugyoDistrictofUganda.AfterconfirmationofsamplestestedbytheUSANationalReferenceLaboratoriesandtheCDC,theWHOconfirmedthepresenceofanewspeciesofEbolavirusthatisnownamedBundibugyo.Theepidemicendedon20February2008.Whileitlasted,149casesofthisnewstrainwerereported,and37provedfatal.(Tower,2008).Thefifthebolavirus,‘Ugandaebolavirus’(‘UEBOV’)wasdiscoveredduringthisoutbreakof2007.Ebolavirusagaincausedanoutbreakthatkilled15andinfected32peopleinsouthernDRCinJanuary2009.AngolacloseddownpartoftheirborderwithDRCtopreventthespreadofEbolaaftertheirexperiencewithMarburgvirusin2 004whichkilled227people.

Finally,therisksoffilovirusresearchweredemonstratedin12March2009,whenanunidentified45yearoldfemalescientistfromGermanyaccidentallyprickedherfingerwithaneedleusedtoinjectEbolaintolaboratorymice.Shewasgivenanexperimentalvaccineneverbeforeusedonhumans.Itremainsunclearwhetherornotshewaseverinfectedwiththevirusoriftheexperimentalvaccineprovedbeneficial.

Asinmostebolavirus-diseaseoutbreaks,itisrecognizedthatburialritualsandcaringofandclosecontactwiththesickcontributedtothespreadoffiloviruses(Gear1975).Mostoftheseoutbreaksbeganwithpeoplewhohadhuntedanimalsintheforestorfounddeadanimalsandconsumedthem.ThemechanismoftransmissionofinfectionintheEbolavirusoutbreaksismainlybydirectcontactwithinfectedbloodortissue,byverycloseandprolongedcontactwithacutelyillpatients,orbyinoculationwithcontaminatedsyringesandneedles.Transmissionthroughtheairborneroutedoesnotseemtobeafactorinthemaintenanceofanyoftheepidemics.ItisalsothoughtthatespeciallyZaireebolvirusiscausingepizooticsamongcentralchimpanzees(Pantroglodytestroglodytes)andwesternlowlandgorillas(Gorillagorillagorilla),whichmayhavecontributedramaticallytotheirpopulationdecline(Karesh2005).

Naturalreservoirs

ThenaturalreservoiroftheEbolavirusisunknowndespiteextensivestudies,butitseemstoresideintherainforestsontheAfricancontinentandintheWesternPacific.Between1976and1998,variousmammals,birds,reptiles,amphibians,andarthropodsfromoutbreakregionshavebeenstudiedtodeterminethenaturalFiolovirusreservoir.NoEbolaviruswasdetectedapartfromsomegeneticmaterialfoundinsixrodents(MussetulosusandPraomys)andoneshrew(sylvisorexollula)collectedfromtheCentralAfricanRepublic(Peterson2004).Theviruswasdetectedinthecarcassesofgorillas,chimpanzees,andduikersduringoutbreaksin2001and2003,whichlaterbecamethesourceofhumaninfections.However,thehighmortalityfrominfectioninthesespeciesmakesthemunlikelyasanaturalreservoir.

Plants,arthropods,andbirdshavealsobeenconsideredaspossiblereservoirs;however,batsarenowconsideredthemostlikelycandidate.BatswereknowntoresideinthecottonfactoryinwhichtheEbolaindexcasesforthe1976and1979outbreakswereemployed.TheyhavebeenimplicatedinMarburginfectionsin1975and1980.Of24plantspeciesand19vertebratespeciesexperimentallyinoculatedwithEbolavirus,onlybatsbecameinfected(Swanepoel1996).Theabsenceofclinicalsignsinthesebatsischaracteristicofareservoirspecies.Ina2002–2003surveyof1,030animals,whichincluded679batsfromGabonandtheDRC,13fruitbatswerefoundtocontainEbolavirusRNA(Pourrut2009).Asof2005,threefruitbatspecies(Hypsignathusmonstrosus,Epomopsfrangueti,andMyonycteristorquata)havebeenidentifiedascarryingtheviruswhileremainingasymptomatic.StudiesofEgyptianfruitbats(Rousettusaegyptiaxcus)inhabitingtheKitakaCave,UgandaisolatedgeneticallydiverseMarburgvirusRNAfromtissueanddemonstratedvirusspecificantibodies(Towers2009).Todate,Gabonistheonlycountrywherebat(Rousettusaegyptiaxcus)provedtobethereservoirsforbothEbolaandMarburgviruses.Thus,variousspeciesofbatsindicatethattheyarepotentialnaturalhostspecies,orreservoir,offiloviruses.

Restonebolavirus—unlikeitsAfricancounterparts—isnon-pathogenicinhumans.Thehighmortalityamongmonkeysanditsrecentemergenceinpigsmakesthemunlikelynaturalreservoirs.

Epizootics

Ebolavirus

SeveralfilovirusescloselyrelatedtoEbolawereisolatedin1989andearly1990fromsickordyingcynomolgusmacaquesinquarantinefacilitieslocatedinReston,Virginia,inTexas,andinPennsylvania(CDC1990a;Jahrlingetal.1990).ShipmentstoaquarantinefacilityinSiena,Italyin1992alsocontainedanimalsthatdiedwithlaboratory-confirmedEbola-likevirusinfections(WHO1992).ThemonkeysinvolvedineachepizooticimportedfromthePhilippinesandtracedtothesamemajorexportfacilities.TheidentificationofanEbola-likevirusineachfacilityledtotheterminationofallstocks,toreducetheriskofcommunityspread.IntheabsenceofanyestablishedlinkwithAfricaorAfricananimals,theepisodemustrepresentevidenceofAsianfiloviruses.Theanimalsbeingco-infectedwithsimianhaemorrhagicfevercomplicatedthefirstreportedepizooticintheUSA;however,223of1,050exposedanimalsdied.Thenaturalhostandgeographicdistributionisunknown.


of 23


ActivetransmissionwasdocumentedatonePhilippineexportfacility(Hayesetal.1992).AntigencaptureELISAusingliverhomogenatesrevealedthat85outof161(53.2%)monkeysthatdiedwithina3monthperiodprovedpositiveforfilovirusantigen.Theincidencewascalculatedtobe24.4per100animals.Herecaptivemonkeyswereheldingangcages,increasingtheopportunityformonkey-to-monkeytransmissionofvirusbyclosecontactwithvirus-ladenbloodorbodysecretions.Thesourceoftheinfectionremainsunknown.Laboratoryexperimentationalsoshowsthepresenceofhighconcentrationsofviralantigeninpulmonarysecretions,raisingthepossibilitythattheairborneroute(Jaaxetal.1995)mayspreadthisebola-likevirus.Parenteralinoculationwithvirus-contaminatedbloodisanotherpossiblerouteduringtheepizooticsasallmonkeysweretuberculintestedandgivenantibiotics.Thecommonpracticewastoinoculatemanymonkeyswiththesamesyringeandneedle.

Serologicalevidenceoffilovirusexposurewasfoundin12(6%)of186peoplewholivedinwildlifecollectionareasorworkedinprimatefacilitiesinManila(Mirandaetal.1991).Withintheexportfacilityexperiencingtheepizootic,22%ofemployeestestedprovedpositive.Noillnesswasdocumentedinanyofthepositives.IntheRestonfacility,fiveanimalhandlerswereidentifiedashavingahighlevelofdailyexposuretosickanddyinganimals.FourwerefoundbyIFAtohavehadserologicalevidenceofrecentinfection,threeseroconvertingduringtheperiodoftheepizootic.Nofilovirusillnessdeveloped.Noneofthe16contactsofmonkeyswithEbola-likevirusimportedintoItalyshowedanyclinicalorserologicalsignsofinfection.

SincethediscoveryoftheMarburgandEbolaspeciesoffilovirus,seeminglyrandom,sporadicfataloutbreaksofdiseaseinhumansandnon-humanprimateshavegivenimpetustoidentificationofhosttropismsandpotentialreservoirs.DomesticswineinthePhilippines,experiencingunusuallysevereoutbreaksofporcinereproductiveandrespiratorydiseasesyndrome,havenowbeendiscoveredtohostRestonebolavirus(REBOV).AlthoughREBOVistheonlymemberofFiloviridaethathasnotbeenassociatedwithdiseaseinhumans,itsemergenceinthehumanfoodchainisofconcern.REBOVisolateswerefoundtobemoredivergentfromeachotherthanfromtheoriginalvirusisolatedin1989,indicatingpolyphyleticoriginsandthatREBOVhasbeencirculatingsinceandpossiblybefore,theinitialdiscoveryofREBOVinmonkeys.ThediscoveryofanumberofseropositiveabattoirworkersinthePhilippineshavingroutinecontactwiththevirusandseropositiveswinehasraisedconcernaboutthetransmissionofEbolafromanimaltoman(Barrette2009).

TheorigininnatureandthenaturalhistoryofMarburgandEbolavirusesremainunknown.Itwouldseemthatthevirusesarezoonoticandtransmissiontohumansoccursfromongoinglifecyclesinanimals.StudiesattemptingtodiscoverthesourceoftheMarburgoutbreaksinEuropeorAfrica,ortherecentEbolaoutbreakintheUSAandItaly,havefailedtouncoverthereservoir.Whatevertheirsource,person-to-persontransmissionisameansbywhichoutbreaksandepidemicsprogress.Thisinvolvesclosecontact;secondarycaseshaverarelyexceeded10%,indicatingthattransmissionisnotefficient.Nosocomialinfectionisaspecialcase;extremecareshouldbetakenwhendealingwithinfectedblood,secretions,tissues,andhospitalwaste.

Preventionandcontrol

Prevention

Withoutanunderstandingofthenaturalhistoryoftheviruses,ecologicalcontrolscapableofpreventingthesporadichumancasesthathavestartedoutbreaksandepidemicsinthepastareimpossible.Theexceptionwouldbethecontainmentofmonkeys,whichmighthavetheinfections.WhilethereisastrongsuspicionthatEbolaandMarburgdiseasesarezoonoses,thesearchcontinuesfortheoriginandreservoirhost(s)ofthevirus.

Controlstrategies

AlthoughbothMarburgandEbolainfectionsarerareevents,theyrepresentadangerousnosocomialhazard.Promptidentificationofactivecasesisessentialandisdependentuponanaccurateanddetailedhistory(DepartmentofHealthandSocialSecurityandWelshOffice1986;CDC1995;WHO1995b).Itisclearfromthefilovirusepidemicsencounteredtodatethathospitalshaveactedasthemainamplifierofthediseasetothecommunity.Therefore,itisimportantthatphysiciansworkingintheareaswherehaemorrhagicfeversoccurshouldbeawarethatthesediseasesexistandthatnosocomialspreadisahighpossibilityifnotrecognizedearlyandpatientsplacedincompleteisolationunderbarriernursingconditions.Innon-endemicareas,itisimportanttomaintainawarenessofthecurrentviralepidemiologicaldevelopmentsandthethreatofimportation.Preventionofperson-to-personspreadofthevirusisessentialtocontrol.Threeweekspriortoillnesspatientsathighestriskhavetravelledintoareaswhereviralhaemorrhagicfever(VHF)hasrecentlyoccurred;haddirectcontactwithblood,bodyfluids,secretions,orexcretionsofapersonoranimalwithVHF;orworkedinalaboratoryorfacilitythathandlestheviruses.ThelikelihoodofacquiringEbolaorMarburgisextremelylowifpatientsdonotmeetanyofthecriteria.Contactsofsuchpatientsmustbeplacedundersurveillanceandnotallowedtotravel.High-riskcontactisassociatedwithdirectcontactwithbloodorbodyfluidsfromacutelyillhumansoranimals;sexualcontactwithaconvalescentcase;orthroughlaboratoryaccidents.Thus,effectivesurveillanceofhigh-riskcontactsandisolationoffurthercasesensuresrapidcontrolofanoutbreak.Thecauseoffeverinpatientsreturningfrom


of 23


MarburgandEbolaendemicareasismorelikelytobeotherinfectiousdisease(malariaortyphoid);therefore,evaluationandtreatmentofsuchinfectionsneedsurgentattention.

Patientcontainment

Controlofoutbreaksinendemicandnon-endemicareashasbeenassociatedwiththeintroductionofgoodhospitalandlaboratoryinfectioncontrolpractices,withtheisolationoffebrilepatients,carefulhandlingoflaboratoryspecimensandrigoroususeofglovesanddisinfectants.Thecontainmentofpatientsinplastic-filmpatientisolators(Trexlar)isfavouredintheUK(DepartmentofHealthandSocialSecurity(DHSS)andWelshOffice1986).Thesearelocatedwithinaroomhavingfilterednegativeairpressuregradients,aseparateeffluenttreatmentplantforwaste,anin-suiteautoclaveforsolidwaste,ashower,andastaffchangingroom.Manyconsiderthatthepatientisolatorreducesmanualdexterity,introducesfatigue,inhibitstheeffectivenessofintensivecareprocedures,andhinderscommunication.Ofmostconcernisthattheseisolatorsdonotreducetheriskofinjurybyanysharpinstrumentsandhavenoprovisionforresuscitation.ThissystemisnotusedinendemicareasorrecommendedintheUSA(CDC1995)sincethemainrisksareassociatedwithdirectinoculationofvirusinbloodorothermaterialandtheaerosolhazardconsideredlowrisk.Thus,itisrecommendedtoconfinepatientstoisolationinasingleroomwithorwithoutcontrolledfilteredair.Themostimportantconsiderationisstafftrainingandsupervision,theuseofglovesandmasks,andthemandatoryuseofadisinfectionpolicy.TherecommendationsissuedconcerningthemanagementofAIDSpatientsareconsideredadequateforcontainmentofFiloviruses.

TherepatriationtoSwitzerlandofanacutelyillEbolacaseoriginatingintheCôted’Ivoirein1994andMarburgcasefromUgandatotheNetherlandsin2008demonstratestheneedforvigilance,sincefilovirusinfectionwasnotconsideredordiagnoseduntilthepatienthadrecovered.Hadthenormalbarrierprecautionsnotbeenundertaken,thepotentialforspreadcouldhavebeendevastating.Filovirus-infectedpatientsshouldbeisolatedandbarrier-nursedtopreventsecondaryinfections.Handling,transportation,andtestingofclinicalmaterialcontainingahighconcentrationofvirusesshouldfollowinternationalandnationalguidelines.

Primateguidelines

Asnon-humanprimatesareknowntohaveintroducedMarburgtoEurope,andEbolatotheUSandItaly,themanagementoftransportationandquarantinefacilitiesshouldensurethatpersonnelunderstandthehazardsassociatedwithhandlingnon-humanprimates.Althoughtheriskofinfectionislow,guidelineshavebeenissuedtominimizesuchrisksinpersonsexposedtonon-humanprimatesduringtransportandquarantine(CDC1990b;WHO1990).Thoseatriskofinfectionincludepersonsworkingintemporaryorlong-termholdingfacilitiesandpersonswhotransportanimalstothesefacilities(cargohandlersandinspectors).Monkeys,particularlythoseimportedfromAfricaandAsia,arepotentialsourcesofarangeofdiseases,andsevereillnessordeathsinrecentlyimportedprimatesshouldbereportedtohealthandveterinaryauthoritiesandinvestigatedforavarietyofinfectiousagents,includingEbola.

Captivemonkeysfrequentlyheldingangcagesincreasetheopportunityformonkey-to-monkeytransmissionbyvirus-ladenbloodorbodysecretions.StudiesoftheepizooticintheUSAandexperimentalinfectionstudieshavefoundhighconcentrationsofviralantigeninpulmonarysecretions,raisingthepossibilitythatfilovirusesspreadthroughtheaerosolroute.

AlthoughthenewlyrecognizedEbolavirusfromAsiaapparentlycausesafataldiseaseincynomolgusmacaques,initialevidenceindicatesthatitsabilitytoproduceinfectioninhumansmaybelessthanthatoftheEbolaandMarburgvirusesfromAfrica.However,becauseoftheknownseverityofdiseasecausedbyothermembersoftheFiloviridae,itwouldbeprematuretoignorethepossibilityofapossiblepublichealththreatposedbytheAsianfiloviruses.FourindependentaccountsconcerningtheimportationofFiloviridae-infectedprimatesintotheUSAandEuropefromtwoareasoftheworld,AsiaandAfrica,increasetheimportanceofintroducinganinfrastructurefortherecognition,identification,andeliminationpolicestoremovethepossibilityofspread.

Thehighdegreeoftransmissibilityamongmonkeyshousedinconfinedconditionsindicatestheneedforearlyidentificationofinfectedanimals,bothtoprotectthemonkeysandtominimizetheriskofhumaninfection.Theearlydetectionoffilovirusantigenaemiaornucleicacidwouldallowidentificationofinfectedanimalsbeforetheybecomeill.Whethertheireliminationwouldpreventanyoutbreakhasyettobeproven.Atpresent,thepotentialthreatfromfilovirusantibody-positiveanimalsremainsunclear,althoughthereisnoevidencethatlatentorconstantinfectionhasplayedanyroleinmonkey-associatedoutbreaks.Improvedquarantineandanimalhandlingproceduresneedtobeuniversallyimplementedtoensurenofutureoutbreaksassociatedwithwild-caughtmonkeys.Therefore,contactbetweenmonkeysandmanshouldbelimitedandanimalhusbandrytightlycontrolled.Personnelhandlinganimalsshouldwearprotectiveclothing,includingrubberglovesandfacerespirator.Allanimalwaste,cages,andotherpotentiallycontaminateditemsshouldbetreatedwithappropriatedisinfectants.

Finally,theincreasedconcernforwildlifeconservationandlicensingofexporters/importerswillfurtherdecreasetherisk


of 23


offilovirusspreadtoman.

ReferencesBaron,R.,McCormick,J.,andZubeir,O.(1983).EbolavirusdiseaseinsouthernSudan:hospitaldisseminationinintrafamilialspread.Bull.WorldHeal.Organ.,61:997–1003.

Barrette,R.W.etal.(2009).DiscoveryofSwineasaHostfortheRestonebolavirus.Sci.,325:204–6.

Baskerville,A.,Fisher-Hoch,S.P.,Neilds,G.H.,andDowsett,A.B.(1985).UltrastructurepathologyofexperimentalEbolahaemorrhagicfevervirusinfection.J.Path.,147:199–209.

Bausch,D.G.,Nichol,S.T.,Muyembe-Tamfum,J.J.,etal.(2006).Marburghemorrhagicfeverassociatedwithmultiplegeneticlineagesofvirus.N.Engl.J.Med.,355:909–19.

Bwaka,M.A.etal.(1999).EbolaHemorrhagicFeverinKikwit,DemocraticRepublicoftheCongo:ClinicalObservationsin103Patients.J.Infect.Dis.,179(suppl.1):S1–S7.

Bishop,D.H.L.andPringleC.R.(1995).OrderMononegavirales.In:F.A.Murphyetal.(ed.)VirusTaxonomy,SixthReportoftheInternationalCommitteeonTaxonomyofViruses,pp.265–67.Vienna:Springer-Verlag.

Bitekyerezo,M.C.etal.(2002).TheoutbreakandcontrolofEbolaviralhaemorrhagicfeverinaUgandanmedicalschool.Trop.Doct.,32:10–15.

Borio,L.etal.(2002).HemorrhagicFeverVirusesasBiologicalWeapons-MedicalandPublicHealthManagement.JAMA,287:2391–2405.

Bowen,E.T.W.,Platt,G.S.,Lloyd,G.(1977).ViralhaemorrhagicfeverinsouthernSudanandnorthernZaire:preliminarystudiesontheaetiologicagent.Lancet,1:571–73.

Bwaka,D.G.etal.(1999).EbolaheamoorhagicfeverinKikwit,DemocraticRepublicoftheCongo:ClinicalObservationsin103patients.J.Infect.Dis.,179(suppl.):S1–S7.

CentersforDiseaseControl(1990a).Ebolavirusinfectioninimportedprimates�Virginia,1989.MMWR,38:831–38.

CentersforDiseaseControl(1990b).Ebolarelatedfilovirusinfectioninnon-humanprimatesandinterimguidelinesforhandlingnon-humanprimatesduringtransitandquarantine.MMWR,39:22–30.

CentersforDiseaseControl(1995c).Managementofpatientswithsuspectedviralhaemorrhagicfever�US.MMWR,44:475–79.

DepartmentofHealthandSocialSecurityandWelshOffice(1986).Thecontrolofviralhaemorrhagicfevers.London:HMSO.

DepartmentofHealth(2007).TransportofInfectiousSubstancesBestPracticeGuidanceforMicrobiologyLaboratories.http://www.dh.gov.uk/publications.

Elliot,L.H.,McCormick,J.B.,andJohnson,K.M.(1982).InactivationofLassa,Marburg,andEbolavirusesbyGammairradiation.J.Clin.Microbiol.,16(4):704–8.

Emond,R.T.D.(1978).Isolation,monitoring,andtreatmentofacaseofEbolainfection.In:S.R.Pattyn(ed.)Ebolavirusinfection,pp.27–32.Amersdam:Elsevier/NorthHollandBiomedicalPress.

Emond,R.T.D.,Evans,E.,Bowen,E.,andLloyd,G.(1977).AcaseofEbolavirusinfection.BMJ,2:541–44.

Feldman,H.,Klenk,H.D.,andSanchez,A.(1993).Molecularbiologyandevolutionoffiloviruses.Arch.Virol.Suppl.,7:87–100.

Feldmann,H.,Nichol,S.T.,Klenk,H.D.,Peters,C.J.,andSanchez,A.(1994).CharacterizationofFilovirusesBasedonDifferencesinStructureandAntigenicityoftheVirionGlycoprotein.Virol.,199:469–73.

Feldmann,H.etal.(2007).Effectivepost-exposuretreatmentofEbolainfection.PLoSPathog.,3(1):e2.

Fisher-Hoch,S.P.,Platt,G.S.,Lloyd,G.,Simpson,D.I.,Neils,G.H.,andBarett,A.J.(1983).HaematologicalandbiochemicalmonitoringofEbolainfectioninrhesusmonkeys:implicationsforpatientmanagement.Lancet,2:1055–58.


of 23


Fisher-Hoch,S.P.etal.(1985).Pathophysiologyofshockandhaemorrhageinafulminatingviralinfection(Ebola).J.Infect.Dis.,152:887–94.

Fisher-Hoch,S.P.,Perez-Oronoz,G.I.,Jackson,E.L.,Hermann,L.M.,andBrown,B.G.(1992a).Filovirusclearanceinnon-humanprimates.Lancet,340:451–53.

Fisher-Hoch,S.P.etal.(1992b).Pathogenicroleofgeographicoriginofprimatehostandvirusstrain.J.Infect.Dis.,166(4):753–63.

Formenty,P.,Hatz,C.,LeGuenno,B.,Stoll,A.,etal.(1999).HumanInfectionDuetoEbolaVirus,SubtypeCôted’Ivoire:ClinicalandBiologicPresentation.J.Infect.Dis.,179(suppl.1):S48–S53.

Formenty,P.etal.(2003).OutbreakofEbolahemorrhagicfeverintheRepublicoftheCongo,2003:anewstrategy?Med.Trop.(Marseille),63(3):291–95.

Gear,J.S.S.etal.(1975).OutbreakofMarburgvirusdiseaseinJohannesburg.BMJ,4:489–93.

Geisbert,T.W.andJahrling,P.B.(1990).UseofimmunoelectronmicroscopytoshowEbolavirusduringthe1989UnitedStatesepizootic.J.Clin.Pathol.,43:813–16.

Geisbert,T.W.etal.(2009).Single-InjectionVaccineProtectsNonhumanPrimatesagainstInfectionwithMarburgVirusandThreeSpeciesofEbolaVirus.J.Virol.,14(83):7296–7304.

Georges,A.J.,etal.(1999).EbolahemorrhagicfeveroutbreaksinGabon,1994–1997:epidemiologicandhealthcontrolissues.J.Infect.Dis.,179:S65–75.

Gibb,T.R.,Norwood,D.A.,Woollen,N.,andHenchal,E.A.(2001).Developmentandevaluationofafluorogenic5′nucleaseassaytodetectanddifferentiatebetweenEbolavirussubtypesZaireandSudan.J.Clin.Microbiol.,39:4125–30.

Grolla,A.,Lucht,A.,Dick,D.,Strong,J.E.,andFeldmann,H.(2005).LaboratorydiagnosisofEbolaandMarburghemorrhagicfever.Bulletin.Soc.Pathol.Exotic.,98:205–9.

Haas,R.andMass,G.(1971).ExperimentalinfectionofmonkeyswiththeMarburgvirus.In:G.A.MartiniandR.Siegert(eds.)Marburgvirusdisease,pp.136–43.Berlin:Springer-Verlag.

Hayes,C.G.etal.(1992).OutbreakoffatalillnessamongcaptivemacaquesinthePhilippinescausedbyanEbola-relatedfilovirus.Am.J.Trop.Med.Hyg.,46:664–71.

Henderson,B.E.,Kissling,R.E.,Williams,M.C.,Kafuko,G.W.,andMartin,M.(1971).EpidemiologicalstudiesinUgandarelatingto‘Marburgagent’.In:G.A.MartiniandR.Siegert(eds.)Marburgvirusdisease,pp.19–23.Berlin:Springer-Verlag.

Heymann,D.L.,Weisfeld,J.S.,Webb,P.A.,Johnson,K.M.,Cairns,T.,andBerquist,H.(1980).Ebolahaemorrhagicfever:Tandala,Zaire,1977–1978.J.Infect.Dis.,56:247–70.

Jaax,M.etal.(1996).TransmissionofEbolavirus(Zairestrain)touninfectedmonkeysinabiocontainmentlaboratory.Lancet,343:1669–71.

Jahrling,P.B.etal.(1990).Preliminaryreport:isolationofEbolavirusfrommonkeysimportedtoUSA.Lancet,335:502–5.

John,S.P.,Wang,T.,Steffen,S.,Longhi,S.,Schmaljohn,C.S.,andJonsson,C.B.(2007).TheEbolaVirusVP30isanRNABindingProtein.J.Virol.,81:8967–76.

Johnson,E.D.,etal.(1996).CharacterizationofanewMarburgvirusisolatedfroma1987fatalcaseinKenya.Arch.Virolol.,11:101–14.

Karesh,W.,andReed,P.(2005).EbolaandgreatapesinCentralAfrica:currentstatusandfutureneeds.Bull.Soc.Path.Exotic.,98:237–38.

Kiley,M.P.etal.(1982).Filoviridae:ataxonomichomeforMarburgandEbolaviruses?Intervirol.,18:24–32.

Ksiazek,T.G.,Rollin,P.E.,Jahrling,P.B.,Johnson,E.,Dalgard,D.W.,andPeters,C.J.(1992).EnzymeimmunosorbentassayforEbolavirusantigensintissuesofinfectedprimates.J.Clin.Microbiol.,30:947–50.

Ksiazek,T.G.etal.(1999).ClinicalvirologyofEbolahemorrhagicfever(EHF):virus,virusantigen,andIgGandIgMantibodyfindingsamongEHFpatientsinKikwit,DemocraticRepublicoftheCongo,1995.J.Infect.Dis.,179:S177–87.


of 23


Ksiazek,T.G.,West,C.P.,Rollin,P.E.,Jahrling,P.B.,andPeters,C.J.(1999).ELISAforthedetectionofantibodiestoEbolaviruses.J.Infect.Dis.,179(Suppl.1):S192–98.

Kuzmin,I.V.etal.(2010).MarburgVirusinFruitBat,Kenya.Emerg.Infect.Dis.,16(2):352–54.

LeGuenno,B.,Formentry,P.,Wyers,M.,Gounon,P.,Walker,F.,andBoesch,C.(1995).IsolationandpartialcharacterisationofanewstrainofEbolavirus.Lancet,345:1271–74.

Leroy,E.M.etal.(2000).DiagnosisofEbolahaemorrhagicfeverbyRT-PCRinanepidemicsetting.J.Med.Virol.,60:463–67.

Martini,G.A.(1969).Marburgagentdiseaseinman.Trans.R.Soc.Trop.Med.Hyg.,63:295–302.

Martini,G.A.(1971).Marburgvirusdisease,clinicalsyndrome.In:G.A.MartiniandR.Siegert(eds.)Marburgvirusdisease,pp.1–9.Berlin:Springer-Verlag.

Miranda,M.E.G.,White,M.E.,Dayrit,M.M.,Hayes,C.G.,Ksiazek.T.G.,andBurns,J.P.(1991).SeroepidemiologystudyoffilovirusrelatedtoEbolainthePhilippines[letter].Lancet,337:425–26.

Miranda,M.E.etal.(1999).EpidemiologyofEbola(subtypeReston)virusinthePhilippines,1996.J.Infect.Dis.,179(Suppl1):S115–19.

Mason,C.(2008).ThestrainsofEbola.Can.Med.J.,178:1266–67.

Modrof,J.,Becker,S.,andMühlberger,E.(2003).EbolaVirusTranscriptionActivatorVP30IsaZinc-BindingProtein.J.Virol.,77:3334–38.

Nikiforov,V.V.(1994).AcaseofMarburgviruslaboratoryinfection.Zh.Mikrobiol.Epid.Immun.,3:104–6,(Russian).

Noda,T.etal.(2006).Assemblyandbuddingofebolavirus.PlosPathogensSeptember;e99.Publishedonline2006September29.doi:10.1371/journal.ppat.0020099.

Okware,S.I.etal.(2002).AnoutbreakofEbolainUganda.Trop.Med.Int.Heal.,7:1068–75.

Peters,A.,Sanchez,R.,Swanepoel,B.,andVolchkov,V.E.(2005).FamilyFiloviridae.,In:C.M.Fauquet,M.A.Mayo,J.Maniloff,U.Desselberger,andL.A.Ball(eds.),VirusTaxonomy-EighthReportoftheInternationalCommitteeonTaxonomyofViruses.p.645–53.SanDiego,CA:Elsevier/AcademicPress.

Peterson,A.T.,Bauer,J.T.,Mills,J.N.(2004).Ecologyandgeographicdistributionoffilovrusdisease.Emerg.Infect.Dis.,10:40–47.

Piot,P.,etal.(1978).ClinicalAspectsofEbolaVirusInfectioninYambukuArea,Zaire,1976.In:S.R.Pattyn(ed.),EbolaVirusHaemorrhagicFever,pp.7–14.Amsterdam:Elsevier/North-HollandBiomedicalPress.

Pourrut,X.,etal.(2005).ThenaturalhistoryofEbolavirusinAfrica.MicrobesInfect.,7:1005–14.

Pourrut,X.,etal.(2009).LargeserologicalsurveyshowingcocirculationofEbolaandMarburgvirusesinGabonesebatpopulations,andahighseroprevalenceofbothvirusesinRousettusaegyptiacus.BioMed.Cen.Infect.Dis.,9:159–69.

Pratt,W.D.etal.(2010).ProtectionofNonhumanPrimatesagainstTwoSpeciesofEbolaVirusInfectionwithaSingleComplexAdenovirusVector.Clin.Vacc.Immun.,17:572–58.

Pringle,C.R.(1991).OrderMononegavirales.Arch.Virol.,117:137–40.

Reid,S.P.,Valmas,C.,Martinez,O.,Sanchez,F.M.,andBasler,C.F.(2007).EbolavirusVP24proteinsinhibittheinteractionofNPI-1subfamilykaryopherinαproteinswithactivatedSTAT1.J.Virol.,81:13469–77.

Richman,D.D.,Cleveland,P.H.,McCormick,J.B.,andJohnson,K.M.(1983).AntigenicAnalysisofStrainsofEbolaVirus:IdentificationofTwoEbolaVirusSubtypes.J.Infect.Dis.,147:268–71.

Rollin,P.E.,Ksiazek,T.G.,Jahrling,P.E.,Haines,M.,andPeters,C.J.(1990).DetectionofEbola-likevirusesbyimmunofluorescence.Lancet,336:1591.

Saijo,M.,Niikura,M.,Ikegami,T.,Kurane,I.,Kurata,T.,andMorikawa,S.(2006).LaboratoryDiagnosticSystemsforEbolaandMarburgHemorrhagicFeversDevelopedwithRecombinantProteins.Clin.Vacc.Immunol.,13(4):444–51.

Sanchez,A.,Kiley,M.P.,Klenk,H.D.,andFeldman,H.(1992).SequenceanalysisoftheMarburgvirusnucleoprotein


of 23


gene:comparisontoEbolavirusandothernon-segmentednegativestandRNAviruses.J.Gen.Virol.,73:347–57.

Sanchez,A.,Kiley,M.P.,Holloway,B.P.,andAsuperin,D.D.(1993).SequenceanalysisoftheEbolavirusgenome:organisation,geneticelements,andcomparisonwiththegenomeofMarburgvirus.Vir.Res.,29:215–40.

Smith,D.G.,Francis,F.,andSimpson,D.I.H.(1978).AfricanhaemorrhgicfeverinthesouthernSudan,1976:theclinicalmanifestations.In:S.R.Pattyn(ed.)Ebolavirushaemorrhagicfever,pp.1–6.Amsterdam:Elsevier.

Smith,D.H.etal.(1982).Marburg-virusdiseaseinKenya.Lancet,1:816–20.

Swanepoel,R.,Leman,P.A.,Burt,F.J.(1996).ExperimentalinoculationofplantsandanimalswithEbolavirus.Emerg.Infect.Dis.,2:321–25.

Teepe,R.G.etal.(1983).AprobablecaseofEbolavirushaemorrhagicfeverinKenya.E.Afric.Med.J.,60:718–22.

Timen,A.etal.(2009).ResponsetoImportedCaseofMarburgHemorrhagicFever,theNetherlands.Emerg.Infect.Dis.,15(8):1171–75.

Towner,J.S.etal.(2004).RapidDiagnosisofEbolaHemorrhagicFeverbyReverseTranscription-PCRinanOutbreakSettingandAssessmentofPatientViralLoadasaPredictorofOutcome.J.Virol.,78:4330–41.

Towner,J.S.etal.(2007).MarburgVirusInfectionDetectedinaCommonAfricanBat.PLoSOne,2:articlee764[EpubAug.22,2007]http://www.plosone.org.

Towner,J.S.etal.(2008).NewlydiscoveredEbolavirusassociatedwithhemorrhagicfeveroutbreakinUganda.PLosPathogens,4(11):e1000212.doi:10.1371/journal.ppat.1000212.

Towner,J.S.etal.(2006).MarburgvirusgenomicsandassociationwithalargehemorrhagicfeveroutbreakinAngola.J.Virol.,80:6497–516.

Weik,M.,Modrof,J.,Klenk,H.D.,Becker,S.,andMühlberger,E.(2002).EbolaVirusVP30-MediatedTranscriptionIsRegulatedbyRNASecondaryStructureFormation.J.Virol.,76:8532–39.

WorldHealthOrganizationInternationalCommissiontoSudan.(1978a).EbolahaemorrhagicfeverinSudan;1976.Bull.WorldHeal.Organ.,56:247–70.

WorldHealthOrganization/InternationalCommissiontoZaire(1978b).EbolahaemorrhagicfeverinZaire;1976.Bull.WorldHeal.Organ.,56:271–93.

WorldHealthOrganization(1990).Interimguidelinesforhandlingnonhumanprimatesduringtransitandquaratine.Wkly.Epidemiol.Rec.,65:45–52.

WorldHealthOrganization(1992).Viralhaemorrhagicfeverinimportedmonkeys.Wkly.Epidemiol.Rec.,67:142–43.

WorldHealthOrganization(1995a).Ebolahaemorrhagicfever,Zaire.WeeklyEpidemiol.Rec.,70:241–42.

WorldHealthOrganization(1995b).Viralhaemorrhagicfevers�managementofsuspectedcases.Wkly.Epidemiol.Rec.,35:249–52.

WorldHealthOrganization(1995c).Ebolahaemorrhagicfever�confirmedcaseinCôted’IvoireandsuspectedcasesinLiberia.Wkly.Epidemiol.Rec.,70:359.

WorldHealthOrganization(1996).Ebolahaemorrhagicfever.WklyEpidemiol.Rec.,71:320.

WorldHealthOrganization(2003).Outbreak(s)ofEbolahaemorrhagicfever,CongoandGabon,October2001–July2002Wkly.Epidemiol.Rep.,78(26):223–25.

WorldHealthOrganization(2004).EbolahaemorrhagicfeverintheRepublicoftheCongo—Update6.Wkly.Epidemiol.Rec.,6January.

WorldHealthOrganization(2005).OutbreakofEbolahaemorrhagicfeverinYambio,southSudan,April–June2004.WklyEpidemiol.Rec.,80:370–75.

WorldHealthOrganization(2007).Ebolavirushaemorrhagicfever,DemocraticRepublicoftheCongo—Update.Wkly.Epidemiol.Rec.,82:345–46.

WorldHealthOrgaization(2007).GuidanceonregulationsforthetransportofinfectiousSubstances


of 23


www.who.int/csr/resources/publications/biosafety/WHO_CDS_EPR_2007_2cc.pdf.

WorldHealthOrganization(2007).Marburghaemorrhagicfever,Uganda.WklyEpidemiol.Rec.,82:297–8.

WorldHealthOrganization(2008).CaseofMarburgHaemorrhagicFeverImportedintotheNetherlandsfromUganda.10July.

WorldHealthOrganization(2009).EbolaRestoninpigsandhumans,Philippines.WklyEpidemiol.Rec.,84:49–50.

Wulff,H.andJohnson,K.M.(1979).ImmunoglobulinMandGresponsesmeasuredbyimmunofluorescenceinpatientswithLassaorMarburgvirusinfections.Bull.WorldHeal.Organ.,57:631–35.

Zaki,S.R.etal.(1999).AnovelimmunohistochemicalassayforthedetectionofEbolavirusinskin:implicationsfordiagnosis,spread,andsurveillanceofEbolahemorrhagicfever.CommissiondeLuttecontrelesEpidemiesaKikwit.J.Infect.Dis.,179(Suppl.1):S36–47.

oxford medicinescsml.rssi.ru/info/ebolavirus/marburg_and_ebola_viruses.pdf · oxford medicine...

Documents