The eradication of smallpox.

Henderson's paper in the October 1976 issue of Scientific American was one of the first published announcements of the completion of the eradication of smallpox. Illustrating the iconic photograph of a mother holding an infected child in her arms, Henderson wrote: “The three year old girl recovering from smallpox was the last known victim in Bangladesh and thus the world’s last known case of the more virulent form of the disease, variola major." He added,  "The patient, three year old Rahima Banu, was the world’s last known case of the severe form of smallpox, variola major. After that 12,000 health workers supervised by nearly 100 epidemiologists repeatedly searched Bangladesh house by house. They found no cases, and it is unlikely that any more will be discovered, but surveillance will continue for two years."

(Thanks to Juan Weiss for this reference and its interpretation.)