Flashcards in skin 4: smallpox Deck (33):
smallpox (Variola major) is ??
A large dsDNA virus that replicates in the cytoplasm of infected human cells.
Variola major belongs to ??
Orthopox virus group that includes:
Variola major morality ??
Reasons why smallpox was eliminated:
Humans are the only host and sole reservoir.
There is no carrier state (no persistently infected but asymptomatic individuals).
Readily recognizable with only a rare subclinical case
Long incubation – vaccination can protect contacts of infected
Highly effective vaccine
variola virus is transmitted:
-Via respiratory droplets: talking, coughing and sneezing
-From skin lesions to mucosa –rarely intact skin
-Fomites, i.e., clothes or bed linens of person with smallpox.
-During prodromal period but less efficiently than during the exanthem
variola major spreads quickly or slowly ??
Spreads slowly within a community. Primary attack rate- 20 and 40% but has been shown to vary between 2 and 80%. Variations depend on
Severity of the index case
Susceptibility of the community as a whole
variola major may be contagious even before ??
s/s appear. Persons are contagious until all lesions have healed (pox have separated and fallen off)
Clinical manifestations smallpox: there are multiple forms but ?? is the most common
Variola major is the most common form of smallpox.
Variola incubation is ??
During this period, there is replication of the virus in the ??
followed by spread to the ??
once replication occurs here, there is a ??
draining lymph nodes.
*minor viremia* in
which the virus spreads to the liver, spleen, lung, bone marrow, etc.
Once replication occurs in the organs, there is a ?? with seeding of the skin with virus during this phase.
The smallpox major viremia gives rise to an acute onset days of prodromal symptoms during which, the pt. may be infectious:
high fever (40oC / 104oF) with chills
The fever may wanes after 2-4 days and the ?? begins to appear as the fever declines.
There is often an ?? one or two days before the appearance of the 1st?
The smallpox exanthem and enanthem are painful!
*enanthem*: over tongue, mouth and oropharynx
*exanthem*: *centrifugal pattern* first appears on first on the face, concentrated on extremities, palms of the hands and soles of the feet.
Rash progresses from *macules to papules, then vesicles, then pustules to scabs* (Pustules will *umbilicate*)
Lesions (pox) are in the same stage of development are deep within the dermis. It may take 8-13 days before scabbing occurs.
*Patient is contagious until all scabs separate fall off!*
other smallpox virus associated symptoms
Pneumonia or pneumonitis – enanthem in lungs
Vomiting – enanthem in g.i. tract.
arthritis in children; variola keratitis, encephalitis, Secondary bacterial infection and/or bacterial superinfection of skin or respiratory tract (bacterial pneumonia)
T-cell and antibody
clinical presentation. There are several lab tests but most do not distinguish between smallpox and other orthopoxviruses.
-The presence of eosinophilic intracytoplasmic inclusions (Guarnieri bodies) on smears and biopsies of lesion material or black intracytoplasmic inclusions on silver stains may confirm the clinical diagnosis.
-Immunodiffusion (gel) tests.
Cidofovir (Vistidetm) is a nucleoside phosphonate DNA polymerase inhibitor.
the smallpox vaccine - vaccina virus vaccine.
Can be administered both *pre- exposure* and, if provided in a timely fashion, *post-exposure*
The basis for its protection is that there is a high degree of antigenic similarity (cross-reactivity) between it and the smallpox virus
Multiple vaccine preps available and in development. Not a benign vaccine
Administered with a bifurcated needle using scarification. Three stabs to nonimmune (not
previously immunized) and 15 stabs to immune (previously immunized) individuals.
"normal" responses to smallpox (vaccina) vaccine
Local infection and lesion formation - scar.
Pustular lesion at the injection site leaving a depigmented scar
Flu-like symptoms of fever, malaise, headache, etc.
Adverse side effects of the vaccina vaccines:
-Est. 1,250 persons/million vaccinated will have an adverse reaction: 1 person/million vaccinated will die of some side effect.
-Progressive vaccina or vaccina gangrenosa – very rare necrotic
manifestation in individuals with occult immunosuppression.
-Eczema vaccinatum - local or systemic infection in persons with a history of eczema.
-Recent vaccination has yielded evidence of pericardiomyopathy
-The immunosuppressed & unvaccinated persons inadvertently infected by
vaccinated persons are at higher risk for adverse reactions.
-Most adverse reactions are due to autoinoculation (e.g. eye) and can be prevented by education while others can be prevented by rigorous screening and exclusion criteria.
with all the complications, should we use vaccina virus vaccine ??
and if yes, for whom ??
regardless of potential adverse reactions, it is recommended that all persons exposed to a known source of smallpox (e.g. infected patient) should be vaccinated.
It is estimated that solid protection lasts ?? following immunization and partial immunity (infection possible but with significantly modified disease course) is assured within ??
Some indication that vaccination at any point in life is likely to provide at least some partial immunity??
3 to 5 years
3% vs. 30% mortality rate!
variola vs. varicella: incubation period
small: 7-17 days
chicken: 14-21 days
variola vs. varicella: prodrome
smallpox: 2-4 days
chicken pox: Minimal if present (adults and adolescents)
variola vs. varicella: distribution
chicken pox: centripetal
variola vs. varicella: palms and soles?
chicken pox: NO
variola vs. varicella: evolution
chicken pox: asynchronous
variola vs. varicella: pock penetration
smallpox: deep dermis
chicken pox: superficial
variola vs. varicella: scabs form in ??
smallpox: 10-14 days
chicken pox: 4-7 days
variola vs. varicella: scabs separate in ??
smallpox: 14-28 days
chicken pox: less than 14 days