Medical Microbiology

422 8 VirusesasHumanPathogen

TheinitialinfectionwithVZVmanifestsinthegreatmajorityofpersons

aschickenpox,anepisodicpapulousexanthem.Theportalsofentryarethe

nasopharyngealspaceandtheconjunctiva.Fromthere,thevirusundergoes

aviremicphaseinwhichitistransportedbythebloodtotheskin,wherethe

typicalexanthemisproduced.Thediseaseconfersaneffectiveimmunity.In

immunodeficientpatients,aVZVinfection(orreactivation,seebelow)can

affectotherorgans(lungs,brain)andmanifestasevere,frequentlylethal,

course.

Afterthesymptomsofchickenpoxhaveabated,theVZVpersistsinthe

spinalgangliaandperhapsinothertissuesaswell.Followingreactivation,

zoster(shingles)develops(Fig.8. 6 ),wherebythevirusonceagainspreads

neurogenicallyandcausesneuralgiaaswellasthetypicalzosterefflorescence

intheskinsegmentsuppliedbythesensitivenerves.Reactivationisinduced

byinternalorexternalinfluencesandbecomespossiblewhencellularVZV

immunitydropsoff,i.e.,afterabouttheageof 45 assumingnormalimmune

defenses.

Diagnosis.VZVcanbedetectedwithawidespectrumofmethods,namely

PCR,isolation,directviraldetectionbymeansofelectronmicroscopy,detec-

tionofviralantigensusingimmunofluorescenceintissuespecimensorcell

smears,andserologicallybasedonantibodytiterincreasesorIgMdetection.

Epidemiology,prevention,andtherapy.VZVishighlycontagiousandis

transmittedaerogenically.Theprimaryinfection,whichmanifestsaschick-

enpox,isstillalmostexclusivelyachildhooddiseasetoday.Avaccinecontain-

ingattenuatedvirusesisavailableforpreventionofchickenpoxandpossibly

zoster,butitsuseiscurrentlyamatterofcontroversy.Inimmunosuppressed

patients,hyperimmunoglobulincanbeusedforpassiveimmunizationor

postexposure immunity.Acycloguanosine is used bothprophylactically

andintreatmentofVZVinfections.

Herpeszoster

Fig.8. 6 Thevaricellazos-

terviruses(VZV)persistin

thelatentstateinspinal

gangliacells.Whenreacti-

vated,theycausedermal

efflorescencesinthecorre-

spondingdermatome.

8

Kayser, Medical Microbiology © 2005 Thieme