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30 Cards in this Set

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  • Back
VZV Clinical Features
origionaly thought it was 2 diff viruses
1)1o, varicella or "chickenpox"
– systemic / disseminated viral disease
2)reactivated, zoster or "shingles"
- localized viral disease w/ neuronal spread to an affected dermatome
VZV Chickenpox characteristics
- mild febrile illness of kids
- disseminated vesicular rash of clear blisters w/ irregular red margin
– resolved in a few wks(no scar)
Lesion form: macules -> papules -> vesicles -> pustules -> scabs
headache and malaise: -> pruritic(itching) rash -> low fever/irritability
VZV chickenpox complications
1) 2o infections of lesions, w/ risk of subsequent septicemia
2) post-infectious encephalomyelitis(self limiting, fine in immunocompetent kids)
3) pneumonia if immunocompromised, high mortality(more b/c immunosupp therapy)
4) Varicella pneumonia-1o inf in adults, serious b/c cell to cell spread via Fusion
5) Reye’s syndrome-acute encephalopathy (aspirin)
VZV Shingles characteristics
- reactivation of latent VZV
- like chicken pox, but larger lesions on the dermatome innervated by infected sensory nerve
- may be very painful
- usually develops when immunosuppresed (so odds increase w/ age)
VZV shingles complications
post-herpetic neuralgia(70% of patients)
a)hypersensitive to touch and T extremes
b)may persist for months(episodic or constant)
mild to severe
VZV Properties of the Virus
- like herpes simplex virus(same struct/replic)
- enveloped - so easily inactivated(heat, detergents, organic solvents)
- rapid replication and ease of transmission so hard to exploit enviro fragility
Pathogenesis of Primary Varicella-Zoster Infection
- non-specific binding in the nasopharynx
- initial replication in resp epi -> regional LNs -> viremia to liver and spleen
- 2o viremia mediated by PBMCs -> transports virus to cutaneous epi(rash) and resp mucosal sites(spreads to other non-imune host)
- w/ hematogenous and neural spread -> latent state in the sensory nerve ganglia following 1o inf
- asymptomatically shed throughout the host’s life
VZV Epidemiology and Transmission
- universal childhood infection
- spread by resp droplet
- shed prior to symptoms(avoidance=difficult)
- both are non-seasonal and non-epidemic
- maternal protection for first six months
- immunity primarily cell-mediated
- 1o disease confers lifetime immunity to 1o
- but shingles(2o) may develop if immunocomp (age-80yr=50% risk fo shingles)
– then protected from shingles
VZV Diagnosis
- based on presentation and contact history
1) Tzanck smear from vesicles- syncytia, intranuclear inclusion bodies
2) fluorescent Ab detect virus in lesions
- culture provides the definitive diagnosis but is difficult(growth in vitro is poor)
VZV Prevention and Treatment
- kids over 1 yr get one attenuated vaccine
- Acyclovir (or penciclovir) may terminate the viremia, reduce shedding, lessen severity
- Zoster immune globulin given to exposed non-immunes
- testing, live-attenuated, varicella "booster" vaccine for people >60 to stop shingles
- US('95-'00)drop in varicella in all age groups b/c of increased vaccine coverage
Cytomegalovirus (HCMV) Clinical Features
Presents differently among:
- normal immunocompetent
- fetuses
- immunosuppressed
HCMV Immunocompetent inf
- 1o = unremarkable, usually in childhood, subclinical
- most adults seropositive
- in (-) adults, 1o often from children shedding in urine, saliva and feces, or intimate contact w/ shedding adult
- adult 1o -> mild pharyngitis or EBV-like mono(fever,lymphocytosis), Mild hepatitis
- after 1o, symptoms cease; viral shedding falls but may recur
-Latent in Lymphocytes, heart, Kidneys
Cytomegalovirus Congenital Infection
- if infected for the first time in pregnancy, may transmit to fetus
- in 1st trimester -> severe birth defects
- if later; rarely-> congenital abnormalities
- (+) women w/ recurrent infection rarely transmit it, if they do, infants=less affected
- Affected babies may appear normal, but have progressive damage to NS, esp hearing
- most common congenital viral inf, leading cause of NS abnormalities
Cytomegalovirus Immunosuppressed
- may develop severe disease after 1o or re-act infection:
1)interstitial pneumonia
4)disseminated disease
1)a high % of AIDS patients shed
2) ½ have infection at somepoint
- primary post-transplant infection, esp bone marow
Cytomegalovirus Properties of the Virus
- like herpes (HHV-5)
- largest herpesviruses genome
- it has a restricted host range
- it is sensitive to heat, low pH, lipid solvents (envelope)
Cytomegalovirus Pathogenesis and Immunity
- outcome determined by host immunity
- 1o inf in salivary gland epi -> asymptomatic viremia and shedding(in immunocompetent)
Cytomegalovirus Epidemiology and Transmission
- ubiquitous everywhere, more in urbar areas(b/c of need for close contact to spread)
- humans only reservoir
- in all body fluids->all types of close contact transmits
- (+) can shed for years
a) often in transfused blood
b) daycare kids
c) immunocomp shedding more
d) (+) moms milk(maybe highest mode of transmition)
Cytomegalovirus Diagnosis
- hard to say it's a cause b/c it's everywhere
- subclinical in most
- misdiagnosed as EBV.
- likely the cause of mono if EBV heterophile antigen test is negative
1)found in WBCs by immunofluorescence.
2)shell vial assay detects w/in within 24 hours.
3a)in immunocomp - serology for IgM and IgG
3b)in congenital - culture infant’s urine and saliva
3c)in immunosup - culture a biopsy
Cytomegalovirus Prevention and Treatment
- no good treatment
- no viral TK, so no acyclovir or penciclovir
- ganciclovir(dG analog) works, b/c a viral protien kinase will phosphorylate it
a)GCV much more toxic and expensive than ACV/penciclovir
Poxviruses Clinical Diseases
- Smallpox(variola major/minor)
- Vacinnia
- Molluscum contagiosum
- Zoonotic poxviruses
Poxviruses Clinical Disease Smallpox
- eradication in 1977
- presented as either variola major or minor(less virulent form)
- rash began as macules -> papules -> vesicles -> pustules -> crusts
- loss of scabs=severe scarring/pockmarks
- major form of had 10 - 30% mortality, partly due to disruption in food production(starvation)
- Monkeypox in African is transmissible to human(clinical features=identical to smallpox)
Poxviruses Clinical Features Vaccinia
- Less-virulent relative of variola(used as propylaxis of variola for 200yrs)
- following subcutaneous inoculation->papule at site
- lesion has same pattern as smallpox w/out spreading(w/ scab and characteristc vaccination scar)
- Rarely->sequelae(e.g. auto-inoculation of cornea, systemic vaccinia in immuno-incompetent
Poxviruses Clinical Features Molluscum contagiosum
- self-limiting infection of the skin
- small umbilicated nodules w/ small white cores
- may last from months to years(spontaneously resolving)
- increased severity in AIDS
- increasing frequency in genital infections->heightened awareness
Poxviruses Clinical Features Zoonotic poxviruses
- transmitted by direct contact to humans
- occupational hazard
- self-limiting lesions on hands or face
- orf virus of sheep or goats
- cowpox, bovine pustular stomatitis and pseudocowpox of cattle(cowpox=cats too)
Poxviruses Properties
- large, dsDNA
- brick-shape virion of complex structure
- replication, transcription and prot synth occur in the cytoplasm
- have DNA-dependent RNA poly in nucleocapsids
Poxviruses Pathogenesis
- inhalation of variola ->replication in URT, LRT -> infection of Macs -> Macs migrate to regional LNs where virus replicates -> 1o cell-associated viremia (still asymptomatic and non-infectious)
- replication in the spleen and bone marrow -> 2o viremia and replication in small vessels of dermis
- migration of inf Macs to epidermis -> characteristic symptoms
- inf of Oropharyngeal epi -> spread to other hosts
Poxviruses Epidemiology and Transmission
- variola virus only shed during acute infection
- outbreaks in rural area got all age groups
- in urban = only kids(b/c frequent exposure)
- monkeypox is relatively rare and less transmissible('97 outbreak in Congo had high human-human transmition), but just as serious
Poxviruses Diagnosis
- not part of differential diagnosis of vesicular rash
- most related viruses ass. w/ animals or travel, take careful history
Poxviruses Prevention and Treatment
- vaccination for lab workers handling it
- eradication worked b/c:
1) humans only reservoir
2) 1 serotype
3) all = symptomatic
4) predictable epidemics
5) recovered patients recognized by lesions
6) vaccine very stable when dried
7) vaccinees marked by vaccination scar
- encodes a (TK) that does not Phosphorylate ACV so ACV not effective
Poxvirus immunity
- development of humoral immunity = important in recovery and protection from re-infection
- natural variola inf -> lifetime immunity