A highly contagious disease, smallpox is caused by infection with the variola virus. A person with this condition will typically develop raised bumps that appear on the face and body (the name smallpox is derived from the Latin word for "spotted").
Thanks to a concentrated vaccination effort, the last natural U.S. outbreak of this potentially fatal disease occurred in 1949. By 1972, routine vaccinations for children in the United States were no longer required. No cases of naturally occurring smallpox have occurred worldwide since 1980.
After the events of September and October 2001, many people are concerned that the variola virus might be used as an agent of bioterrorism. The deliberate release of smallpox is now regarded as a possibility, and the United States is taking precautions to deal with this threat.
(To read more about this disease, including how the different types of smallpox are classified, click Smallpox.)