What Is It?
Smallpox is a contagious and sometimes fatal disease caused by two related viruses: variola major and variola minor. Variola major is the more common and severe form, with an overall historical fatality rate of about 30%. Variola minor is less common and causes a milder form of smallpox that is usually not fatal. Historic death rates were less than 1%. Smallpox eradication was one of the greatest successes of modern public health. Through a sophisticated global vaccination campaign, the World Health Organization officially declared in 1980 that smallpox had been eliminated worldwide. The last known case of smallpox in the United States occurred in 1949, and the last case of naturally occurring smallpox was reported in 1977 in Somalia.
Today, the smallpox virus is known to exist only in secured laboratory stockpiles in the United States and Russia. However, it is theorized that other countries may have possession of the virus as well.