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.
Human extinction Human extinction In futures studies, human extinction is the hypothetical end of the human species. This may result from natural causes or it may be the result of human action. The likelihood of human extinction in future by wholly natural scenarios, such as a meteorite impact or large-scale volcanism, is generally considered to be extremely low. For anthropogenic extinction, many possible scenarios have been proposed: human global nuclear annihilation, biological warfare or the release of a pandemic-causing agent, dysgenics, overpopulation, ecological collapse, and climate change; in addition, emerging technologies could bring about new extinction scenarios, such as advanced artificial intelligence,