Medical Microbiology

RNAviruses 457

smallchildrenindevelopingcountries; 20 %oftheseinfectionsaredueto

rotaviruses.Inthetemperatezone,rotavirusesareimplicatedinfewerindi-

vidualinfections;heretheymorefrequentlycausewinteroutbreaksinhos-

pitalsandhomesforsmallchildren.Rotavirusesremainviableforlongper-

iodsonobjectsandskin(hands!)andarethereforespreadrapidlybyinfected

personsandhealthycarriers.Themosteffectiveprophylacticapproachisto

practicestringenthygiene.

ViruseswithSingle-StrandedRNAGenomes,

Antisense-StrandOrientation

SixviralfamilieshaveanantisenseRNAgenome:theOrthomyxoviridae,the

Bunyaviridae,theArenaviridae,theParamyxoviridae,theRhabdoviridae,and

theFiloviridae.JustlikeallotherRNAviruses,theyrequireaRNA-indepen-

dentRNApolymerase,whichentersthecellwithintheviralparticleinthe

infectiveprocess.

Rotaviruses

1 00 nm

Fig.8. 15 TEMimageofrotavirusesinstool

fromaninfantsufferingfromdiarrhea.Allof

thevirusesinthefamilyReoviridaepossessa

doubleicosahedralcapsid.Theoutercapsid

hasadiameterofapproximately 70 nm,the

innercapsidapproximately 40 nm.Itcon-

tainsthesegmentedRNAgenome,compris-

ingfrom 10 to 12 double-strandedsubunits

dependingonthespecies.

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Kayser, Medical Microbiology © 2005 Thieme