Medical Microbiology

RNAviruses 471

Filoviruses(MarburgandEbolaViruses)

&TworelatedAfricanvirusesaresubsumedunderthenamefiloviruses,

MarburgandEbola.Thesepathogenscausehemorrhagicfeverswithhigh

lethalityrates.ThefewdescribedMarburgvirusoutbreaksapparentlyin-

volve monkeypopulations. Ebola outbreaks are apparently becoming

morefrequent.Thenaturalreservoirofthefilovirusesisunknown.

Diagnosis:byantigenassay,EM,andisolation. &

Pathogen.TheMarburgviruswasisolatedforthefirsttimein 1967 asaresult

ofthreesimultaneousoutbreaksamonglaboratorystaffinMarburg,Frank-

furt,andBelgrade.Theinfectionvictimshadbeenprocessingtheorgansof

Cercopithecus(Africangreenmonkeys)fromUganda.BoththeMarburgand

Ebolavirusesarethreadlike, 14 lm-longviralparticles,insomecases

branchedand 80 nmthickindiameter.Theirsurfaceconsistsofanenvelope

ofhost-cellmembranewithviralspikes.Thegenomeconsistsofantisense-

strandRNAinahelicalnucleocapsid 50 nmindiameter.

Pathogenesisandclinicalpicture.TheMarburgandEbolavirusescauseso-

calledhemorrhagicfevers.Theclinicalpicturefirstmanifestswithfever,head-

ache,andneckpain,conjunctivitisanddiarrhea,followedbyhepatic,renal,

andCNSinvolvementandfinally,asaresultofconsumptioncoagulopathy,

leadstoextensivehemorrhagingandterminalshock.Intermsoftheanatom-

icalpathology,nearlyallorgansshowhemorrhagesandfibrindeposits.

Diagnosis.Onlydesignatedlaboratorieswithspecialsafetyfacilitiescanun-

dertakeisolationworkontheseviruses.Detectioniseitherinbloodwithan

electronmicroscopeorusingimmunofluorescenceontissuespecimens.The

pathogenscanbegrownincellcultures.Serodiagnosisisalsopossible.

Epidemiologyandprevention.ThereservoiroftheMarburgandEbola

virusesisunknown.SubsequenttotheMarburgoutbreakin 1967 among

labpersonnelinEurope,MarburgviruseshaveonlybeenfoundinAfrica.

TheEbolavirus,namedafterariverinZaire,hascausedseveraloutbreaks

inAfricasince 1976 inwhichlethalityratesof 50 – 90 %wereobserved.Im-

portedEbolainfectionshavealsobeenseeninmonkeycoloniesinthe

USAandItaly.

Protectivesuitsandvacuum-protectedplastictentsarenolongerrecom-

mendedforhealthcareworkersincontactwithMarburgandEbolapatients

(aswithLassafever),sinceinterhumantransmissionisbyexcretions(smear

infection)andinblood,butnotaerogenic.Despitethisfact,thehighlevelof

infectivityofanyaerosolsfrompatientmaterialmustbekeptinmindduring

laboratoryworkandautopsies.

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Kayser, Medical Microbiology © 2005 Thieme