Smallpox Eradication in India, 1972-1977
The World of Smallpox
Smallpox is caused by a highly contagious virus (Variola major) which is spread through person-to-person contact. It is not related to chickenpox. Early symptoms were high fever and fatigue, followed by a characteristic rash that appeared two to three days later, particularly on the face, arms and legs. The resulting spots filled with clear fluid and pus, which then formed a crust that eventually dried up and fell off. The virus had an incubation period of 7 to 17 days after exposure. A person only became infectious once the fever developed. Although the most infectious period was during the first week of illness, a sick person remained contagious until the last scabs fell off.