On Jan. 8, 2005, researchers from Baylor University Medical Center reported that although the origin of smallpox is lost in prehistory, it is believed to have first appeared at the time of the first agricultural settlements in northeastern Africa around 10000 BCE. From there, it is believed to have spread India through Egyptian merchants.

The earliest evidence of skin lesions resembling smallpox was found on mummies from 18th and 20th Egyptian Dynasties (1570ﾖ1085 BCE). Smallpox was described as early as 1122 BCE in China and was introduced to Europe sometime between the fifth and seventh centuries.