varicella zoster Flashcards
definition of varicella zoster
primary imfection is called varicella (chicken pox)
reactivation of the dormant virus in the dorsal root ganglia –> shingles. AKA herpes zoster
aetiology of varicella zoster
herpes ds-DNA virus
highly contagious
transmission is by aerosol, inhalation or diretc contect with the vesicular lesions
epidemiology of varicella
chickenpox peak incidence 4-10yr
shingles peak incidence occurs at >50yrs
about 90% adults are VZV IgG +ve ie have previously been infected
incubation period of VZV
14-21 days
sx of chickenpox (VZV)
prodromal malaise 1-2d - headache, abdo pain, mild pyrexia
sudden appearance of intensely itchy spreading, erythematous, rash affecting face and trunk more than the extremities, the oropharynx, conjunctivae and GU tract
as vesicles weep and crust over, new vesicles appear
contageiousnfrom 48hr before rash and until all veicles have crusted over - 7-10days
sx of shingles
may occur after period of stress
tingling/hyperaesthesia in dermatomal distribution followed by painful skin lesions (macular then vesicular rash)
disseminated infection if immunocomp
infectious until scabs appear = chicken pox risk in non-immune contacts
recovery in 10-14days
signs of chickenpox
(disseminated varicella)
macular papular rash evolving into crops of vesicles with areas of:
- weeping (exudate) and
- crusting (vesicles, macules, papules and crusts may all be present)
skin excoriation
mild pyrexia
signs of shingles
vesicular macular papular rash
in dermatomal distribution
skin excoriation
pathology of VZV
viral inhalation and infection of the upper resp tract
viral replication in regional LN, liver and spleen
by week 2-3 infection spreads to skin via mononuclear cells producing rash (virus containing vesicles) and then leading to clinical resolution
virus remains latent in dorsal root ganglia - life long
reactivation causes virus to travel down sensory axon to produce dermatomal shingle rash
Ix for VZV
clinical dx
vesicle fluid- electron microscopy, direct immunofluorescence, cell culture, viral PCR (all rarely necessary)
chicken pox - consider HIV testing especially in adults with prior history of VZV infection
management of chicken pox
children - treat symptoms (calaine lotion stop itch, analgesia, antihistamines)
adults - consider oral acyclovir, valaciclovir, or famciclovir of within 24hr of rash onset - IV if elderly, smoker, immunocomp, preg (especially 2nd or 3rd trimester)
shingles treatment
acyclovir, valaciclovir or famciclovir if within 72hrs of appearance of the rash - IV if eldery, immunocomp, or ophthalmic involvement
low dose amitriptyline (tricyclic anti-depressant) may benefit if moderate/severe discomfort
simple analgesia
prevention of VZV
VZIG may be indicated in immunocomp, neonates and pregnant women exposed to varicellazoster
chickenpox vaccine license in UK - given at age 70 to prevent shingle reactivation
complications of chickenpox
(increase when immunocomp)
secondary infection
scarring
pneumonia
encephalitis
cerebellar syndrome
congenital varicella syndrome
transverse myelitis
pericarditis
purpura fulimans/DIC
what is congenital varicella syndrome
characterised by scarring, opthalmic defects, limb dysplasia and CNS abnormalities
occurs in 1-2% of offspring of mothers who develop chickenpox <20wks gestation
