Pandemic smallpox was responsible for 300–500 million deaths. As recently as the early 1950s, an estimated 50 million cases of smallpox occurred in the world each year. After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in December 1979. To this day, smallpox is the only human infectious disease to have been completely eradicated, and one of two infectious viruses ever to be eradicated. Historically, measles was prevalent throughout the world, as it is highly contagious. According to the U.S. National Immunization Program, 90% of people were infected with measles by age 15.
Extinction considered in regards to non-human species extinction. The poliovirus is now confined to small parts of the world due to extermination efforts. "Dracunculus medinensis", a parasitic worm which causes the disease dracunculiasis, is now close to eradication thanks to efforts led by the Carter Center. "Treponema pallidum pertenue", a bacterium which causes the disease yaws, is in the process of being eradicated. Biologist Olivia Judson has advocated the deliberate extinction of certain disease-carrying mosquito species. In a September 25, 2003 article in "The New York Times", she advocated "specicide" of thirty mosquito species by introducing a genetic element which can