The variola virus causes smallpox. The disease is at least 3000 years old, confirmed in China and India, with a few isolated cases in North Africa. There is no mention in Europe until the 6th century.
During the 17th and 18th Centuries smallpox was the most serious infectious disease in The West and accounted for a substantial proportion of deaths, especially among town dwellers. The mortality rate varied regionally, with 10% in Europe and 90% in America. During the 20th Century, there was recognized for the first time a milder form of smallpox called variola minor or alas trim. It had a consistently low mortality rate of the order of 1%. This disease was endemic in Britain until 1935. Still more recently there has been recognized a third form, named East African Smallpox, the mortality rate of which in unvaccinated subjects is about 5%. This has not been recognized as having occurred in The West.
The plague had eliminated as much as a third of the European population over a five-year period. Smallpox was never that devastating in Europe, becoming endemic and occasionally out breaking. Widespread resistance reduced the losses to local impacts of about 10%. However, introduction of smallpox to America quite rapidly depleted the population. For example, the Spanish attempted to settle Hispania for sugar cane plantation in 1509. By 1518 every single one of the 2.5 million aboriginals had perished, and the labor population had to be restored with African slaves.
Hispania (modern Haiti and the Dominican Republic) were the first site of European contact. Exposure to smallpox during early Spanish attempts to convert the population into plantation slavery exterminated all 3.5 million inhabitants. African slaves replaced them, and this process was repeated throughout the New World for decades.
Cortes introduced smallpox in 1520 during his...