Smallpox is a contagious disease caused by the variola virus that causes a skin rash, pustules and scabs. It is also called variola.

Smallpox killed millions of people worldwide in the past, but was eradicated by 1978 through an immunization program administered by the World Health Organization (an organization of the United Nations concerned with worldwide public health). Routine childhood vaccinations for the disease ended in 1972 in the United States.

In recent years, there has been renewed interest in smallpox because of growing terrorist activity worldwide. Smallpox is among the diseases that could be spread as part of a bioterrorist attack.

There are two types of smallpox, variola minor (a less severe form of the disease) and variola major (a more severe form of the disease). Variola major results in death in about 30 percent of cases, according to the U.S. Centers for Disease Control and Prevention (CDC).

Smallpox is usually spread by having face-to-face contact with an infected person. The virus is contained in air droplets emitted when a person coughs, sneezes or talks.

Smallpox usually starts with flu-like symptoms, such as a high fever and headache. A rash develops on the face and then spreads to the arms, legs, hands and feet. Blisters and pustules form on the skin in later stages of the disease.

Smallpox is diagnosed during a physical examination that includes a medical history and list of medications. The CDC has issued guidelines that assist physicians in recognizing the signs and symptoms of smallpox.

There is no cure for smallpox. Most patients receive supportive therapy, such as intravenous fluids and fever and pain control.