Medical Microbiology

DNAViruses 413

tiosum(“slapped-cheeksyndrome”or“fifthdisease”).Thischildhooddis-

ease,whichusedtobeclassifiedasatypicalmeasles,ischaracterizedbysud-

denonsetofexanthemonthefaceandextremities.Certainformsofarthritis

areconsideredcomplicationsofaparvovirusB1 9 infection.Thevirusalsoap-

pearstocausespontaneousabortionsinearlypregnancyandfetaldamagein

latepregnancy(hydropsfetalis).

Diagnosis.AnenzymeimmunoassayrevealsantibodiesoftheIgGandIgM

classes.Duringtheviremicphase,attheonsetofclinicalsymptoms,thevirus

canalsobeidentifiedinthebloodbymeansofelectronmicroscopyorPCR.

In-vitroculturingofthepathogenisnotstandardprocedure.

Epidemiologyandprevention.Thetransmissionrouteofhumanparvovirus

B1 9 isnotknown.Dropletinfectionorthefecal-oralroute,analogoustoother

parvoviruses,issuspected.Bloodandbloodproductsareinfectious,sothat

multipletransfusionpatientsanddrugaddictsarehighincidencegroups.No

specificprophylacticmeasuresarerecommended.

ViruseswithDouble-StrandedDNAGenomes

Viruseswithdouble-strandedDNAgenomesareclassifiedinsixfamilies:pa-

pillomavirus,polyomavirus,adenovirus,herpesvirus,poxvirus,andhepadna-

virus.Carcinogenictypeshavebeenfoundinallgroupsexceptthepoxviruses

(seeChapter 7 ,DNAtumorviruses).

Papillomaviruses

&Theover 70 viraltypesinthegenusPapillomavirusareallinvolvedinthe

etiologyofbenigntumorssuchaswartsandpapillomas,aswellasmalignan-

cies,thelattermainlyinthegenitalarea(cervicalcarcinoma).Theseorgan-

ismscannotbegrownincultures.Diagnosisthereforeinvolvesdirectdetec-

tionoftheviralgenomeandhistologicalanalysis.Serologyislessimportant

inthisgroup. &

Pathogens.Thepapillomaviruseshaveadiameterof 55 nmandcontainan

8 kbpdsDNAgenome.Therearetwodistinctregionswithinthecircularge-

nome:onethatcodesfortheregulatorproteinsproducedearlyintherepli-

cationcycleandanotherthatcodesforthestructuralproteinssynthesized

later.Over 70 papillomavirustypeshavebeendescribedtodate,allofwhich

induceeitherbenignormalignanttumorsinnaturalorexperimentalhosts.

8

Kayser, Medical Microbiology © 2005 Thieme