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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:
Monkeypox viruses


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
Population density
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 ??

7-17 days
respiratory mucosa
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.

*major viremia*


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
severe headache
back pain


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!


smallpox enanthem/exanthem

*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.


smallpox complications

arthritis in children; variola keratitis, encephalitis, Secondary bacterial infection and/or bacterial superinfection of skin or respiratory tract (bacterial pneumonia)


smallpox immunity

T-cell and antibody


smallpox dx

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.
-PCR (experimental)
-Electron microscopy
-Immunodiffusion (gel) tests.


smallpox tx

Cidofovir (Vistidetm) is a nucleoside phosphonate DNA polymerase inhibitor.


smallpox ppx

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


smallpox vaccine

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.
Other “Normal”responses:
Pustular lesion at the injection site leaving a depigmented scar
Flu-like symptoms of fever, malaise, headache, etc.
Regional lymphadenopathy
Satellite lesions


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.
-Vaccina encephalitis
-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
10 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

smallpox: centrifugal
chicken pox: centripetal


variola vs. varicella: palms and soles?

smallpox: YES
chicken pox: NO


variola vs. varicella: evolution

smallpox: synchronous
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


variola vs. varicella: no longer contagious when ??

smallpox: after separation of scabs
chicken pox: after scabbing

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