Smallpox.

Until the 1970s, smallpox was feared worldwide for the significant morbidity and mortality it caused. Although naturally occurring disease has been eliminated, the virus itself has not been destroyed, and it is assumed that some of the variola stored in the former Soviet Union has been removed. The majority of the world's population is susceptible to smallpox because vaccination ended in 1972 in the United States and in the rest of the world in 1982.