Humanity has completely eliminated exactly one disease from the wild — so far

After a decade-long global vaccination campaign coordinated by the World Health Organization, the last known natural case of smallpox was recorded in Somalia in 1977. In 1980, the WHO formally declared smallpox eradicated, the only human disease ever wiped out entirely.

— World Health Organization, Declaration of Global Eradication of Smallpox — WHO resolution, 1980