Medical Microbiology

RNAviruses 461

Pathogen.ThefamilyBunyaviridaecomprisesover 200 viralspecies,among

themfourhumanpathogengenera:Bunyavirus,Nairovirus,Phlebovirus,and

Hantavirus.Thebunyavirusesarespherical, 80 – 110 nminsize,andposses

envelopeswithspikesformedonmembranesofthesmoothendoplasmicretic-

ulum.Thegenomeconsistsofthreeantisense-strandRNAsegments,whereby

eachsegmentproducesaseparateribonucleoproteincomplex,resultingina

uniquefeatureofthevirion:itcontainsthreehelicalnucleocapsids.

PathogenesisandClinicalPicture.

&GenusBunyavirus:thesevirusesaretransmittedbyarthropods.They

causebenignformsofencephalitissuchasCaliforniaencephalitisandLa-

Crossevirusinfections,bothendemictotheUSA,andtheOropouchevirus

inBrazil.

&GenusNairovirus:themainhumanpathogeninthis groupisthe

Crimean-Congohemorrhagicfevervirus,withalethalityrateashighas

50 %.ThevirusisendemictosoutheasternEurope,CentralAsia,China,Saudi

Arabia,andAfricaandistransmittedbyticksaswellasbydirectcontactwith

infectedanimalsorpatients.

&GenusPhlebovirus:thisgroupincludesthepathogensthatcausethebe-

nignPappataciorphlebotomusfever(“sandflyfever”),whichoccursin

Europe(Italy,Yugoslavia),NorthAfrica,Asia,andSouthAmericaandistrans-

mittedbythephlebotomussandfly.

RiftValleyfever(RVF),anacute,febriledisease,rarelyalsoinvolvinghemor-

rhagicfever,istransmittedbymosquitoesandisendemictoAfrica,usually

followingepizootiesinlivestock,inwhichcaseaerosolinfectionoccurs

(slaughtering).Epidemicshavebeenreportedwithover 200000 casesin

Egyptand 25000 casesinSenegal.Furtherepidemicshaveoccurredin

Somalia,Kenya,andSudan.

&GenusHantavirus:thisgenusincludesseveralviralspecies(orserotypes)

(Table8. 6 )thatcanbeclassifiedintwogroupsaccordingtotheclinicalsymp-

tomstheycause:

&thepathogensofnephropathicaepidemica(NE)andhemorrhagicfever

withrenalsyndrome(HFRS),

&andthehantaviruspulmonarysyndrome(HPS).

Thesourcesofinfectionarerodents(miceandrats).Theinfectionisacquired

byinhalingaerosolsofurine,feces,andanimalsaliva.InNEandHFRSarenal

dysfunctionfollowstheinfluenzalikesymptoms.HPSinfectionresultsina

rapidlyprogressive,acutedyspneawithpulmonaryedemaandislethalin

60 %ofcases.

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Kayser, Medical Microbiology © 2005 Thieme