Smallpox - acute, highly contagious disease causing a high fever and successive stages of severe skin eruptions. The disease dates from the time of ancient Egypt or before. It has occurred worldwide in epidemics throughout history, killing up to 40% of those who contracted it and accounting for more deaths over time than any other infectious disease. Spreading to the New World with European colonization, it killed huge numbers of the indigenous people, who had no immunity, greatly contributing to the annihilation of native cultures.

Smallpox is caused by a virus that may be airborne or spread by direct contact. After an incubation period of about two weeks, fever, aching, and prostration occur, lasting two or three days. An eruption then appears and spreads over the entire body; the lesions become blisterlike and pustular within a week. The lesions then open and crust over, causing itching and pain. When the crusts fall off, usually in another one or two weeks, the extent of permanent damage to the skin (pockmarks) becomes evident. There is no specific treatment for smallpox; an antibiotic may be administered to prevent secondary bacterial infection.

A crude vaccination method began with Emanuel Timoni, a Greek physician, in the early 18th cent. Edward Jenner modified the procedure (1796) by using the related cowpox virus to confer immunity. By 1977, vaccination programs, such as those by the World Health Organization (WHO), had eliminated the disease worldwide.

After 1980, when WHO officially declared smallpox eradicated as a disease, scientists retained some samples of the virus in laboratories for study. They mapped the genetic sequence of three strains of smallpox, and the destruction of the remaining samples of the live virus was scheduled and postponed several times. Owing to fears of a new natural outbreak or of the potential use of smallpox as a terrorist weapon against populations no longer vaccinated, research with the virus continued. The last declared samples of live virus are now stored by the U.S. and Russian governments under strict security, but it is believed that some nations may have secret stores of the virus that they could use as biological weapons. Responding to these concerns, WHO postponed the scheduled 1999 destruction of all remaining stocks of the smallpox virus until 2002. The 2001 bioterror attacks in the United States with anthrax led the United States and other nations to stockpile doses of smallpox vaccine out of concern that the smallpox virus might be used by terrorists, and WHO agreed to delay the destruction of virus stocks beyond 2002 to allow for the development of new vaccines. In 2002, because of bioterrorism concerns, the G. W. Bush administration decided to vaccinate frontline military personnel and health-care and emergency workers against smallpox.

See E. A. Fenn, Pox Americana: The Great Smallpox Epidemic of 1775–1782 (2001), and J. B. Tucker, Scourge (2001).

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