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Indiana State Department of Health

Public Health Preparedness Home > Biological Agents > Smallpox Facts About Smallpox

What smallpox is

  • Smallpox is a serious disease caused by the variola virus that was announced as eradicated, or wiped out, by the World Health Organization in 1980.
  • However, smallpox remains a serious threat due to the possibility that some of the remaining stock, if in the wrong hands, could be grown and adapted for bioterrorism purposes.
  • Smallpox has a fatality rate of 30 percent or more.

How smallpox is spread

  • Smallpox spreads directly from person to person, primarily from the mouth and throat droplets or aerosols from the infected person.
  • In addition, contaminated clothes or linens can also spread the virus.
  • Transmission is highest during the onset of rash through the 7th to 10th days of the rash.
  • As the scabs form, the infectivity of smallpox declines.
  • Because of changes in temperature and humidity, there is more occurrence of smallpox in the winter and early spring.
  • There are no known animal or insect reservoirs or carriers to transmit smallpox.

The symptoms of smallpox are

  • After the incubation period, 10-12 days on average, high fever, malaise, headache, and backache develop.
  • Abdominal pain and delirium or disorientation sometimes occur.
  • Small, colored, bumpy rash begins on the mouth, pharynx, face, and forearms, spreading to the trunk and legs.
  • Within 1-2 days, the rash becomes blisters, and then round and deeply set pimples with pus form in the skin.
  • Within 8-9 days, the pimples with pus become crusted.
  • Scabs separate, leaving pigment-free skin, and eventually pitted scars form.

How smallpox can be treated

  • Treatment of smallpox is limited to supportive therapy and antibiotics for secondary bacterial infections.
  • There are no antivirals, treatments to kill or suppress the virus that have proven to be effective.

The smallpox vaccine

  • There is a vaccination for smallpox. However, routine vaccination stopped in the United States in 1972, and production of the vaccine had ceased by 1980, due to the eradication of smallpox.
  • Those who received the vaccinations before 1972 do not have lifelong immunity because it declines within a 5-10 year period after the vaccination.
  • A limited supply of vaccine still exists in the United States under Center for Disease Control and Prevention authority.
  • Vaccines administered within 3 days of the first exposure have shown to offer some protection against getting infection and significant protection from mortality.

Precautions against smallpox

  • Patients should be isolated or confined in rooms with high air filtration.
  • Standard precautions (gloves, mask, and gown) should be worn.
  • All laundry and waste should be sterilized with steam under pressure before being laundered or destroyed.
  • Standard hospital disinfectants should be used for surface decontamination.