Medical Microbiology

434 8 VirusesasHumanPathogen

ter< 100 IU/l),anattemptshouldbemadetoreachatiterof 100 IU/lwitha

maximumofthreefurthervaccinations.

RNAviruses

ViruseswithSingle-StrandedRNAGenomes,

Sense-StrandOrientation

Todate,sixviralfamilieswithsingle-strandedRNAgenomesinsense-strand

orientationareknown:picornavirus,calicivirus,togavirus,coronavirus,fla-

vivirus,andretrovirus(commonorthography:picornavirus,retrovirus,etc.).

Picornaviruses

&Theimportanthumanpathogenicgeneraofpicornavirusesare:

— Enteroviruseswiththepolioviruses(poliomyelitis),cocksackieviruses

andechoviruses.

— Parechovirusestypes 1 andtype2.

— HepatoviruseswiththehepatitisAvirus.

— Rhinoviruses,commoncoldviruses(rhinitis).

Transmission ofenteroviruses,parechoviruses, andhepatovirusesis by

thefecal-oralroute.Thevirusesfirstreplicateintheintestine,fromwhich

locationtheyreachtheirtargetorganwiththebloodstream.Largenumbers

ofinapparentinfectionsaretypicalofthisgroup.

Rhinovirusesaretransmittedbydropletinfectionandremainrestricted

totheupperrespiratorymucosa.

Diagnosis:enterovirusesandparechovirusesarediagnosedbyisolationin

cellculturesorwithPCR,hepatitisAserologically(IgM)andrhinoviruses,

ifatall,byisolation.

Prevention:basicpolioimmunizationwithdeadorlivevaccine;hepatitisA

withdeadvaccine;exposureprophylaxiswithrhinoviruses. &

Thepicornaviruses(Fig.8. 12 :polioviruses)areamongthemostthor-

oughlystudiedvirusesofall.Thenamepicornaisanabbreviationthatstands

fortwocharacteristicsofthisfamily:theyaresmall(pico)viruseswithanRNA

genome(rna).TheRNAispolyadenylatedatits 30 endandhasnocapatthe 50

end,butinsteadavirus-coded,basicproteinabout 2 kDainsize,theVPg

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Kayser, Medical Microbiology © 2005 Thieme