Smallpox is an infection caused by the variola virus, a member of the poxvirus family. Throughout history, smallpox has caused huge epidemics resulting in great suffering and enormous death tolls worldwide. In 1980, the World Health Organization (WHO) announced that a massive program of vaccination against the disease had resulted in the complete eradication of the virus (with the exception of stored virus stocks in two laboratories).

Smallpox is an extraordinarily contagious disease. The virus can spread by contact with victims, as well as in contaminated air droplets and even on the surfaces of objects used by other smallpox victims (books, blankets, etc.). After acquisition of the virus, there is a 12-14 day incubation period, during which the virus multiplies, but no symptoms appear. The onset of symptoms occurs suddenly and includes fever and chills, muscle aches, and a flat, reddish-purple rash on the chest, abdomen, and back. These...