Smallpox: a disease and a weapon

Essentially, it is impossible to determine when smallpox first infected humans, but evidence suggests that it may have first appeared during the Neolithic Age. The mummified remains of Egyptians, specifically Pharaoh Ramses V (d. 1157BC), provide the first credible evidence of smallpox infection. By the 6th century AD smallpox was firmly rooted in Asia. The Crusades and expanding trade with Asia spread the disease into Europe. From there, the Europeans carried the disease to the New World and by the mid 18th century, the disease was endemic virtually everywhere in the world with the exception of Australia.