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.
Bird extinction which results to the downfall of extinction. The most common disease affecting birds is Salmonellosis, which originates from the Latin name of salmonella. Infected birds pass bacteria in their fecal droppings. Other birds then become ill when they eat food contaminated by the droppings. Bird extinction Out of the approximately 10,400 known bird species, about 1,300 (13%) are classified as threatened with extinction, 9% as near threatened and of the remaining 78% many populations are declining. There is a general consensus among scientists who study these trends that if human impact on the environment continues as it has one-third of