Medical Microbiology

462 8 VirusesasHumanPathogen

Diagnosis.Itispossibletoisolatethevirusfromblood,buttheprocedureis

toodrawn-outandcostlyforroutinediagnostics.Serology(IgMdetection)is

themethodofchoice,althoughtheresultscanbedifficulttointerpretwith

bunyavirusesduetotherapidlychangingantigenicvariantsproducedin

manyoftheviralspecies.

Epidemiologyandprevention.Thebunyavirusesandphlebovirusesare

transmittedbybloodsuckingarthropods,wherebythecycleinvolveseither

humanandvectoronlyor,aswiththetogavirusesandflaviviruses,amam-

mal-arthropod-mammalcycleactuallyindependentofhumans,andinwhich

humanvictimsrepresentadeadendfortheinfectiousagent.Hantaviruses

aretransmittedaerogenicallytohumansfromrodents,inwhichtheviruses

persistapathogenicallyforthelifespanoftheanimal.Themostrecentisolates

oftheHPSpathogenshavealsoapparentlypersistedinthereservoiranimals

foralongtime,withoccasionalhumaninfectionsasshownbyretrospective

analysisofbloodandtissuespecimens.Viraloutbreaksareexplainedbysud-

denplaguesofmice.Preventivemeasuresincludeexposureprophylaxis

(avoidanceofinsectbitesandcontactwithrodents).Anactivevaccination

isavailableforprotectionagainstRiftValleyfever.

Arenaviruses

&Thearenavirusesare“ambisense”viruses,meaningtheypossessgenomic

elementswithminus(antisense)aswellasplus(sense)polarity.Itisquite

possibleforbothcodingorientationstooccurononeandthesamesegment

(ofthesegmentedgenome).Rodentsarethenaturalreservoirofthese

viruses,fromwhichtheycaninfecthumans.AninfectionwiththeLCM(lym-

phocyticchoriomeningitis)virusisnormallyharmless.Bycontrast,infections

Table8. 6 SerotypesofHantaviruses

Serotype Syndrome Geographicdissemination

Hantaan HFRS,severeform Asia,southeasternEurope

Belgrade HFRS,severeform SoutheasternEurope

Puumala NE CentralandnorthernEurope

Seoul HFRS,mildform Worldwide

SinNombre,etc. HPS US,Canada

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Kayser, Medical Microbiology © 2005 Thieme