Small pox has incubation period of 7 to 19 days, usually 10 to 14 days until the start of the illness and another 2 to 4 days until the start of the rash. Others can become infected at anytime from when the rash has developed to when the scabs disappear, an infectious period of about 3 weeks.

Smallpox symptoms begin by emulating those of influenza: a sudden high fever, discomfort , headache, fatigue, and occasional abdominal pain and vomiting. After 2 to 4 days, the fever subsides and a rash appears on the face, typically beginning on the forehead. After that the rash spreads rapidly to the whole face, the extremities, and parts of the torso. This process takes no more than 24 to 36 hours, and once this time period is over no new lesions appear on the skin. 3 to 4 weeks later crusted scabs fall off after the rash has run its course.

Smallpox is treated through a vaccine. Receiving the vaccine within three days of being exposed will prevent or significantly decrease the chance of contracting the virus in the majority of people. Receiving the vaccination four to seven days after exposure can offer some protection and lessen the severity of the virus if contracted. Smallpox was officially pronounced eradicated by the World Health Organization through global vaccination treatments in 1979.

The mortality rate differs from Variola minor and Variola major. Variola minor, because it is a mild form, only has a mortality rate of 1 percent or less. Variola major, however, due to its severity, has an overall mortality rate of anywhere from 15 percent to 45 percent or higher. The fatality rate of Variola major is usually higher in pregnant women and children.

There are some very interesting facts about smallpox. During the French and Indian Wars (1754 to 1763), the British used smallpox as biological warfare against the Native Americans. The virus decimated the Native Americans because they had never been exposed to the virus before, and therefore they did not have immunity. Smallpox was responsible for an estimated 300 to 500 million deaths during the 20th century, and it is only one of two diseases to have ever been eradicated. The last human case was in 1978. The only remaining live smallpox virus stocks are kept at two different World Health Organization reference laboratories.