Wednesday, October 01, 2014
     

Smallpox (Variola Major)

Epidemiology:

  • Highly infectious after aerosolization
  • Person-to-person transmission can occur via droplet nuclei or aerosols expelled from the oropharynx and by direct contact.
  • Contaminated clothing or bed linens can also spread the virus
  • About 30% of susceptible contacts will become infected

Clinical:

  • Incubation period is 12-14 days (ranges 7-17 days)
  • Characteristic rash appears 2-3 days after nonspecific flu-like prodrome (fever and eadache)
  • Maculopapular rash begins on mucosa of mouth and pharynx, face, hands, forearms, and spread to legs and centrally to trunk; lesions are more predominate on the face and extremities than on the trunk.
  • Lesions progress synchronously on any given part of the body from macules to papules to vesicles to pustules to crusty scabs

Laboratory Diagnosis:

  • Mask and gloves should be worn by person obtaining specimen, preferably a person who has been recently vaccinated
  • Vesicular fluid is obtained by opening lesions with the blunt edge of a scalpel, harvesting fluid with a cotton swab; scabs can be removed by forceps. swabs and scabs should be placed in a vacutainer, sealed with tape. and placed in a second, durable, watertight
  • container
  • Laboratory specimens must be handled in a bio-safety level 4 facility (e.g. cdc) and will be evaluated with electron microscopy and cell culture.

Patient Isolation:

  • Airborne isolation in a negative pressure room using N-95 respirator mask from onset of rash until all scabs separate
  • Laundry and waste should be autoclaved before laundered or incinerated

Treatment:

  • Supportive care is the mainstay of therapy
  • In-vitro antiviral activity against poxviruses has been shown with adefovir, idofovir,dipivoxil, and ribavirin (animal studies suggest that cidofovir may be most effective)

Prophylaxis:

  • Smallpox vaccine would be required for all persons exposed at the time of the bioterrorist attack or anyone with close personal contact with a smallpox case
  • Vaccine is most effective if given before or within 3 days of exposure
  • Ideally, all exposed persons should be placed in strict quarantine for 17 days after last contact with a smallpox case