The human disease the World Health Organization declared eradicated in 1980 was smallpox.
Smallpox was caused by variola virus, an orthopoxvirus spread mainly through prolonged close contact. It often began with fever and vomiting before producing a distinctive rash of fluid-filled blisters. Survivors could be left with severe scarring or blindness, and the fatality rate of ordinary variola major was about 30 percent.
Vaccination made eradication possible because humans were the virus’s only natural host and infection produced recognizable illness. The last naturally occurring case was diagnosed in Somalia in October 1977. A separate laboratory-associated case occurred in the United Kingdom in 1978.
A global commission certified eradication on 9 December 1979, and the World Health Assembly formally endorsed it on 8 May 1980. Smallpox remains the only human disease officially eradicated worldwide. That achievement is different from eliminating a disease from one region: eradication means transmission has been stopped globally, apart from retained laboratory virus stocks.