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Micro - Herpes Viruses (ii) (VZV (complications (CNS involvement…
Micro - Herpes Viruses (ii)
VZV
you can't get shingles by being around someone with chickenpox (your own virus must reactivate)
assuming you've never had chickenpox before, you can get chickenpox by being around someone with shingles (not airborne though, must have direct contact with rash)
over 90% of adults are IgG +ve (due to previous primary infection, usually in early childhood)
not a routine vaccine in Ire
highly contagious before + during symptoms
high AR
infection rate = 90% of household contacts
infectious from 2 days before rash onset til lesions have crusted over (become itchy)
Prevention
infection control
don't touch vesicles or fomites
airborne precautions (droplet inhalation)
2 vaccines available
varicella vaccine given to children > 12 months old
Zoster vaccine
prevents shingles in elderly
re-exposure to boost natural immunity
66% efficacy but decreases as age increases
post-exposure Ig given to high risk patients (pregnant/immunocompromised/neonate)
latent in dorsal root N ganglia
reactivation = herpes zoster (shingles)
in 30%
risk increased in elderly (decreasing cell-mediated immunity) + immunosuppressed
classical dermatomal vesicular rash (but can cross dermatomes + diffuse)
pain precedes rash onset, + can persist as post-herpetic neuralgia
can be sight-threatening if it affects ophthalmic division of trigeminal N
incubation = 2-3 wks
fever/irritability followed by vesicular rash (esp on trunk)
most childhood infections not severe (no need for an antiviral)
complications
require acyclovir
bacterial superinfection (GAS, S aureus)
pneumonitis + pneumonia (esp in pregnant women)
CNS involvement
cerebellar ataxia
stroke-like symptoms
encephalitis
death
1 in 60 000 (esp neonates)
severe disseminated infection (esp in kids with ALL)
Congenital varicella syndrome
small risk if mam gets VZV in 1st 20 wks
high risk if mother gets VZV around time of delivery
severe + disseminated
Lab Dx
not required in uncomplicated primary childhood infection (clinical Dx)
PCR on fluid from skin lesions
IgG detection - if -ve person was never infected - vaccine indicated
HHV6
most common cause of roseola infantum
self-limiting childhood illness (most children infected by 2 y/o)
high fever - possible febrile seizures
maculopapular rash
flat erythematous area on skin cover with small confluent blanching bumps
starts on neck/trunk + spreads to extremities
rarely meningitis
can reactivate when immunosuppressed
clinical Dx, no lab tests
integrates into genome in 1%
part of genome
test hair cells to differentiate if its an infection or part of genome
if hair cell +ve then not an infection (viral genome in every cell)
HHV7
another cause of roseola infantum
HHV8
essential for Kaposi's sarcoma
advanced HIV also associated but not essential
poor prognostic indicator
multiple oval violaceous plaques on arms + trunk, following skin relaxed tension lines
transmission = sexual, or horizontal in African children
Linked to AIDS-related body cavity lymphoma (type of non-Hodgkin's lymphoma)