<P> The history of smallpox extends into pre-history ; the disease likely emerged in human populations about 10,000 BC . The earliest credible evidence of smallpox is found in the Egyptian mummies of people who died some 3000 years ago . Smallpox has had a major impact on world history , not least because indigenous populations of regions where smallpox was non-native , such as the Americas and Australia , were rapidly decimated and weakened by smallpox ( along with other introduced diseases ) during periods of initial foreign contact , which helped pave the way for conquest and colonization . During the 18th century the disease killed an estimated 400,000 Europeans each year , including five reigning monarchs , and was responsible for a third of all blindness . Between 20 and 60 % of all those infected -- and over 80 % of infected children -- died from the disease . </P>
when did smallpox transfer from cattle to humans
likely emerged in human populations about 10,000 BC