Smallpox is a contagious viral illness caused by the variola virus. The virus can spread from an infected person through the air when there is fairly prolonged (1-3 hours) direct contact. It can also spread via body fluids, either by direct contact with fluids from an infected person or by touching objects that have been contaminated by infected body fluids. The last documented case of smallpox disease occurred in 1977. However, smallpox is still considered a possible biological threat.
An infected person usually begins to experience symptoms 12 to 14 days after exposure. Smallpox disease results in a fever and viral-like symptoms, followed by a rash that progresses from papules to pustules. Eventually the pustules form scabs and the scabs fall off. People with smallpox can spread the virus to others beginning when their fever is 101°F until all their scabs fall off.
There is no proven cure for smallpox. Historically, death has occurred in about 30% of cases. Giving smallpox vaccine soon after exposure to the virus can help to reduce the effects of smallpox disease. Vaccine given within 3 days after exposure can help prevent death. Vaccine given within 7 days after exposure can result in a less severe (modified-type) smallpox illness.
There is only one smallpox vaccine available in the United States. It is a live, attenuated vaccine made from vaccinia virus. Vaccinia virus is closely related to variola virus, which is the virus that causes smallpox. Immunity against vaccinia virus also provides protection against variola virus. It is administered using a bifurcated needle that is jabbed into the surface of the skin.
To reduce the chance of spreading the vaccine virus to other body parts or other people, please follow these recommendations:
Smallpox is a very serious disease; it is contagious and sometimes fatal. Smallpox is caused by a germ called variola virus.
The symptoms of smallpox begin with high fever, head and body aches, and sometimes vomiting. These symptoms are followed by a rash that spreads from the head and extremities toward the center of the body, then progresses to raised bumps that eventually scab over and fall off after about three weeks, leaving a pitted scar.
Smallpox can cause:
Natural cases of smallpox have been eradicated. The last natural case of smallpox was in Somalia in 1977.
The incubation period for smallpox is about 12 to 14 days (range: 7 to 17 days) after exposure.