1979: After an intense global effort a special commission was able to certify, on 9 December, that smallpox had been eradicated from the world. The last person known to have been infected with naturally occurring smallpox, in October 1977, was Ali Maow Maalin, at the port of Merca, in Somalia. The disease was estimated to have killed 300 million people during the 20th century. The last fatality, in September 1978, was Janet Parker, who was exposed to the virus at the University of Birmingham Medical School.
Source: Ian and Jenifer Glynn, The Life and Death of Smallpox (2004), pp. 225–8