10,000 bc- first agricultural settlements in ne africa . 1122 bc china and mentioned in ancient texts of india. 16th century- became serious disease in england and. New world in 16th century-fall of empires of aztecs and incas. Contributed to settlement of na by french &english (1617) French indian war (1754-1767) deliberate use of smallpox. At least 2 strains exist: variola major and minor. Genus also monkeypox, cowpox, camelpox, chickenpox, and ectromelia (mousepox) viruses. Variola minor- mortality rate less than 2% in unvaccinated ppl. variola major- 3% and 30-50% Hemorrhagic smallpox or black pox: malignant and hemorrhagic forms of variola major develop in approx. 10% of infected ppl- almost always fatal; mortality rate 95% Virus multiplies in mucous membranes of the mouth, nose. lymph nodes internal organs reenters bloodstream. Virus only viable for up to 2 days outside human host. Acute onset- fever, malaise, rigors, vomiting, headache, backache, and occasionally delirium. 2-3 d later skin lesions.