I beg to differ:

"Through the success of the global eradication campaign, smallpox was finally pushed back to the horn of Africa and then to a single last natural case, which occurred in Somalia in 1977. A fatal laboratory-acquired case occurred in the United Kingdom in 1978. The global eradication of smallpox was certified, based on intense verification activities in countries, by a commission of eminent scientists in December 1979 and subsequently endorsed by the World Health Assembly in 1980." (from https://web.archive.org/web/20070921235036/http://www.who.in... )

The Wikipedia page starts with "Smallpox was an infectious disease". I believe this is one of the most powerful sentences I've ever read on the Internet, and it gives me so much hope for what we can achieve.