skin 4: smallpox Flashcards
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:
Vaccina
Cowpox
Monkeypox viruses
Variola major morality ??
30%
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 delirium prostration
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?
exanthem
enanthem
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)
