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.
Voluntary Human Extinction Movement some people consider themselves members of the group but do not actually support human extinction. Knight, however, believes that even if humans become more environmentally friendly, they could still return to environmentally destructive lifestyles and hence should eliminate themselves. Residents of First World countries bear the most responsibility to change, according to Knight, as they consume the largest proportion of resources. Knight believes that Earth's non-human organisms have a higher overall value than humans and their accomplishments, such as art: "The plays of Shakespeare and the work of Einstein can't hold a candle to a tiger". He argues that species