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 plans and supplies for a long isolation. In addition, elaborate bunkers exist for government leaders to occupy during a nuclear war. Any number of events could lead to a massive loss of human life; but if the last few (but see minimum viable population), most resilient, humans are unlikely to also die off, then that particular human extinction scenario is not credible. Eliezer Yudkowsky theorizes that scope neglect plays a role in public perception of existential risks: Substantially larger numbers, such as 500 million deaths, and especially qualitatively different scenarios such as the extinction of the entire human species, seem