With officials debating whether to destroy the remaining specimens of the pathogen, here is a look at notable dates in smallpox history:
1796: Edward Jenner invents a smallpox vaccine.
1966: The World Health Organization (WHO) launches a massive global campaign to eradicate smallpox.
1972: Smallpox vaccinations are discontinued in the United States.
1975 and 1977: The last cases of the two known variants of smallpox occur in the world, in Bangladesh and Somalia.
1978: Two people are sickened in a lab accident in England; one dies.
1980: The WHO declares smallpox eradicated.
1991: Smallpox virus DNA is mapped.
1999: The WHO sets this deadline, by which remaining lab stocks of the virus are to be destroyed. The deadline will be postponed again and again.
2003: Millions of doses of vaccine are produced to hedge against a biological attack.
2011: WHO's decision-making body will meet in May to again vote on whether to kill the remaining live viruses.
SOURCES: "Smallpox Zero," by Jonathan Roy; CDC
