Endemic smallpox was declared eradicated in 1980 by the World Health Organization (WHO). Although two WHO-approved repositories of variola virus remain at the Centers for Disease Control and Prevention (CDC) in Atlanta and at Russian State Centre for Research on Virology and Biotechnology (Koltsovo, Novosibirsk Region) Russian Federation, the extent of clandestine stockpiles in other parts of the world remains unknown. The WHO Advisory Committee on Variola Virus Research recommended that all stocks of smallpox be destroyed by 30 June 2002. However, destruction has been delayed annually since that time by the WHO Health Assembly due to concerns over the need for further study of the virus given its potential as a biological warfare agent.

The United States stopped routinely vaccinating its military population in 1989, but began vaccination again in 2003 for troops deployed to Southwest Asia and the Republic of Korea. Routine civilian vaccination in the United States was discontinued in 1972. Thus much of the population is now susceptible to Variola major. Variola may have been used by the British Army against Native Americans by giving them contaminated blankets from the beds of smallpox victims during the eighteenth century. Japan considered the use of smallpox as a BW weapon in World War II and it has been considered as a possible threat agent against U.S. forces for many years. In addition, the former Soviet Union is reported to have produced and stockpiled massive quantities of the virus for use as a biological weapon. It is not known whether any of these stockpiles may still exist in Russia.

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