Small pox is an ancient and deadly disease. It's believed to have originated more than 3,000 years ago.
In early years, epidemics killed 30 percent of those infected, and often left survivors blind and scared.
In 1796, Edward Jenner, a scientist, demonstrated that inoculation with cowpox could protect against smallpox.
Nearly 200 years later, in 1980, small pox was eradicated worldwide. The virus can live only in humans, not animals or insects, spreading through close contact with an infected person.
Today, the virus is supposed to exist only is repositories in Moscow and the CDC in Atlanta, but experts have suspected that some nations harbor secret stocks of smallpox.