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.
Alliance for Zero Extinction Alliance for Zero Extinction Formed in 2000 and launched globally in 2005, the Alliance for Zero Extinction (AZE) comprises 100 non-governmental biodiversity conservation organizations working to prevent species extinctions by identifying and safeguarding sites where species evaluated to be Endangered or Critically Endangered under International Union for Conservation of Nature (IUCN) criteria only exist at one location on earth. AZE members work to rebuild populations of endangered and critically endangered species through efforts to eliminate human threats such as commercial exploitation, disease and the introduction of invasive species. AZE provides expertise on biodiversity goals for the Convention on Biological Diversity