Smallpox is a disease caused by the variola virus, which has existed for thousands of years. The name smallpox refers to the small red bumps that appear on the skin of the infected. Smallpox is transmitted either by direct contact or small distances through the air.

Two major forms of the disease exist: variola major and variola minor. Variola major is the most common and also the most severe, while variola minor is much more rare (1% of the cases) and has weaker symptoms. However, both forms are potentially fatal and easily spread from human to human.

After a person becomes infected with the virus, there is an incubation period of up to two weeks where the individual does not experience any symptoms. After incubation, the intial symptoms of fever, aches, and vomiting appear for a period of several days. When a rash of small red bumps on the skin appear, the person has entered the third stage and their body will be covered by the rash within a day. Over the next several days, the bumps will become larger and fill with a dark fluid, eventually hardening into scabs over the next two weeks. After scabs have fully formed, they will then begin to fall off of the skin, leaving behind pits of scar tissue.

If a person manages to survive the entire period of infection, they will no longer be contagious after the scabs have fallen off. However, 30% of those infected with variola major and 1% of those infected with variola minor die from the symptoms before reaching the final stage.

Once a person has smallpox, there is currently no way to cure them of the affliction. However, if a person is vaccinated prior to exposure to the virus, the person will not become infected.

Thanks to tremendous efforts by the world population in the 20th century, the disease has been nearly eradicated, except for several samples kept by the United States and Russian governments. It is considered a possibility that terrorists will release smallpox seized from these sources into the general unvaccinated population, allowing the disease cover the earth once again. However, if such an event were to occur, the world would be more capable of quarantining the outbreak and vaccinating the population than ever before.