Smallpox , a deadly disease that has plagued humanity for thousands of years, has a history that extends into pre-history. Genetic evidence suggests that the smallpox virus emerged 3,000 to 4,000 years ago. The earliest physical evidence of smallpox is found in the Egyptian mummies of people who died some 3,000 years ago. The Scourge of Smallpox Smallpox had a major impact on world history. Indigenous populations of regions where smallpox was non-native, such as the Americas and Australia , were rapidly and greatly reduced by smallpox during periods of initial foreign contact. 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. During the 20th century, it is estimated that smallpox was responsible for 300–500 million deaths . The Battle...