<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> <P> During the 20th century, it is estimated that smallpox was responsible for 300--500 million deaths . In the early 1950s an estimated 50 million cases of smallpox occurred in the world each year . As recently as 1967, the World Health Organization estimated that 15 million people contracted the disease and that two million died in that year . After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the global eradication of smallpox in December 1979 . Smallpox is one of two infectious diseases to have been eradicated, the other being rinderpest, which was declared eradicated in 2011 . </P>

When did smallpox transfer from cattle to humans