SMALLPOX

Smallpox is a virus that can be caught through direct contact with someone infected with smallpox. In a terrorist attack, exposure to smallpox could occur by breathing a sprayed airborne virus.

Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from one person to another.  Animals and insects do not carry or spread the smallpox virus.

A person who has been exposed to smallpox becomes contagious after a rash appears and remains contagious until the last smallpox scab falls off. 

Exposure to smallpox is followed by an incubation period during which people do not have any symptoms and may feel fine. This incubation period averages about 12 to 14 days, but can range from seven to 17 days. During this time, people are not contagious.

The first symptoms of smallpox include fever, malaise, head and body aches and sometimes vomiting. The fever is usually high, in the range of 101 to 104 degrees. At this time, people are usually too sick to carry on their normal activities. This phase may last for two to four days.

A rash emerges first as small red spots on the tongue and in the mouth. These spots develop into sores that break open and spread large amounts of the virus into the mouth and throat. At this time, the person is the most contagious.

Within 24 hours, a rash appears on the skin, starting on the face and then spreading to the arms and legs and then to the hands and feet. Usually the rash spreads to all parts of the body within 24 hours. As the rash appears, the fever usually falls and the person may start to feel better.

By the third day, the rash becomes raised bumps.

By the fourth day, the bumps fill with a thick, opaque fluid and often have a depression in the center that looks like a belly-button. (This is a major distinguishing characteristic of smallpox.) Fever often will rise again at this time and remain high until scabs form over the bumps.

During the next five to 10 days, the bumps become "pustules" -- sharply raised, usually round and firm to the touch. They feel like there's a small round object under the skin. People often say it feels like there is a BB pellet embedded under the skin.

Days 11-14, the pustules begin to form a crust and then scab. By day 14, most of the sores have scabbed over.

Days 15 - 21, the scabs begin to fall off, leaving marks on the skin that eventually become pitted scars. The person is contagious to others until all of the scabs have fallen off. Most scabs will fall off after three weeks.

After the 21st day, scabs have fallen off. Person is no longer contagious.

Humans are the only natural hosts of smallpox which is caused by the variola virus that emerged in human populations thousands of years ago. Except for laboratory stockpiles, the virus has been eliminated as a disease.

« this page last modified 04/03/07 »