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Updated: January 2006
It’s a virus. (The scientific name of the most common and deadly form of the disease is Variola major.) Smallpox is ancient; descriptions of the disease have been found dating from the 4th century A.D. in China, and less reliable evidence even points to cases as far back as 1200 B.C.
The World Health Organization officially declared smallpox eradicated in 1979, after a painstaking vaccination campaign. The last known human case of naturally-contracted smallpox was in Somalia in 1977. Samples of the virus remain in labs at the Centers for Disease Control and Prevention (CDC) in Atlanta and in labs in Russia.
Extremely. It can spread like the common cold, through person-to-person contact and through the air. Contaminated clothing or bed linens can also spread the virus. Symptoms may develop anywhere from seven to seventeen days after exposure. An infected person is contagious only after symptoms develop.
Historically, smallpox has killed about 30 percent of those it has infected. The mortality rate varies with health and age (small children and the elderly are the most vulnerable). The disease can also cause complications such as encephalitis (an inflammation of the brain) and blindness. Smallpox is one of the most devastating diseases known to humankind, having killed between 300 and 500 million people in the twentieth century alone.
Early symptoms include fever, fatigue, head- and backaches, and vomiting. About two or three days after symptoms begin, a rash appears, mostly on the face, arms, and legs. The rash starts out raised and pink and turns to pus-filled lesions. Early in the second week, these crust over. Scabs separate and fall off after about three or four weeks. An infected person is contagious from the time symptoms appear until the time the last scabs fall off.
Smallpox lesions tend to appear on the face and extremities, especially the palms of the hands and soles of the feet; chicken pox sores appear more frequently on the torso. Smallpox lesions develop at the same time; chicken pox sores usually develop in clusters. Smallpox lesions go deeper into the skin than chicken pox sores and leave disfiguring scars.
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