Fact sheet on smallpox

Clinical Features:

Incubation: 7-17 days

Natural History

  • Febrile 2-4 days with fever, rigors, malaise, headache, backache, and vomiting (Occasionally delirium, transient early rash)
  • Acute papular dermatitis on face, hands, forearms, spreading to lower extremities and trunk
  • Synchronous progression: papule to vesicle to pustule
  • Scabs over on days 8-14 after onset of fever
  • Scabs slough off 14-28 days after fever onset

Expected Delivery Method(s)

  • Infected persons entering and mingling with local residents. This would be difficult to execute, as the period of maximum viral shedding is after the patient becomes obviously ill.
  • Aerosol release
  • Point source
  • Line source
  • Both of these would be difficult, as the agent has not been successfully weaponized in the West.



  • Patients and clothing are highly contagious.
  • Clothing and linen must be sterilized in an autoclave or by boiling.
  • Hard surfaces can be cleaned with quartenary ammonium, phenolic, or 5% bleach solutions. Allow contact for at least four hours.


  • Patients, linens, and everything else the patient touched are highly contagious, as is the area in which droplets from the patient may have landed.


  • Strict isolation is required. This requires a combination of:
  • Contact isolation
  • Droplet precautions
  • Universal precautions
  • Cohorting of patients is encouraged.
  • Contacts need to be immunized and quarantined for 17 days.
  • Home quarantine also is an option, but will require supports (such as food deliveries) to allow people to remain at home for the duration.


  • Immunization is usually protective if done within 24 hours of exposure.


  • First, do everything possible to limit spread.
  • Use primarily supportive care.
  • There is a Smallpox Immune Globulin, but its supply is limited, as is its efficacy.
  • Cidofovir may be effective.

Source: Charles Werntz, MD, Department of Community Medicine, West Virginia University, Morgantown, and Janet Williams, MD, West Virginia University Center for Rural Emergency Medicine, Morgantown.