How Much Do You Know About Smallpox?

Smallpox is caused by the variola virus, a member of the orthopoxvirus family. When smallpox was prevalent, it had two main forms: variola major and variola minor. Both forms developed similar skin lesions, but the minor form was much less deadly; variola major killed about 30 percent of those infected with it.

After a person is exposed to or comes in contact with the smallpox virus, there is an incubation period of 12 to 14 days, during which time it causes no symptoms. During this period, the person is not infectious. Once a fever develops, the person can spread the virus through direct and prolonged face-to-face contact, particularly through coughing. Fluids from the blisters of a person with smallpox are infectious. It is not spread by insects or animals.

According to the Centers for Disease Control and Prevention (CDC), one confirmed case of smallpox would be considered a public health emergency.

After the incubation period, the first symptoms of smallpox appear. They resemble the flu: fever of 101 to 104 degrees, headache, back pain, body aches, malaise, and, occasionally, vomiting. These initial symptoms are called the prodrome phase and last two to four days. The person is sometimes contagious. Two to three days after these symptoms begin, a rash appears, first on the tongue and in the mouth. The rash sores break open and spread the virus in the mouth and throat. The person is most contagious at this time. A rash also breaks out on the skin, beginning on the face. This spreads to the arms and legs, and then to the hands and feet. Within 24 hours, the rash has spread to all parts of the body. The rash progresses to raised bumps called pustules that fill with fluid and often have a depression in the middle resembling a bellybutton. This is a “hallmark” sign of smallpox. A person is still contagious during this time. These bumps break open and release viruses. Then a crust forms, and about two weeks after symptoms begin, the bumps form scabs. These scabs contain virus also. A person with smallpox is contagious until all the scabs have fallen off. When the scabs fall off, scars remain on the skin.

Chickenpox lesions are less extensive and are more likely to be concentrated on the trunk than on the face, arms, and legs.

When smallpox was prevalent, up to 80 percent of people stricken with smallpox came away with deeply pitted scars on the face and other areas of the body. Before smallpox was eliminated, up to a third of all cases of blindness were caused by the disease.

Currently, no treatment is available to cure smallpox, but the disease can be prevented with the smallpox vaccine. Medication can also be given to help ease symptoms and treat any bacterial infections that may occur. Smallpox infection with variola major is fatal in up to 30 percent of those who contract it. Research is ongoing to find a drug that can be used to treat smallpox.

What's crucial is to keep the virus from spreading. All people who have been in contact with the infected person should be vaccinated. Anyone involved in treating the infected person also should be vaccinated.

Because smallpox does not now occur anywhere in the world, there no longer is a national vaccination program for this disease. The last routine vaccinations for smallpox in this country were given in 1972. Currently, only certain health care workers, emergency response personnel, and military personnel have been given the vaccine. Vaccination usually prevents smallpox infection for at least 10 years. If an outbreak of smallpox does occur, people who are in contact with those infected with the virus can be vaccinated. The vaccine, if given up to four days after exposure and before the rash appears, can prevent smallpox infection. The vaccine is a live virus related to smallpox; it does not contain smallpox and cannot cause it. In people who were vaccinated as children, any subsequent infection with the virus might cause only a mild form of the disease, health experts say.

The health care provider uses a two-pronged needle that is dipped into the vaccine. The health care provider pricks the skin of the upper arm with the needle several times. The pricking causes a sore spot on the arm. If the vaccine is successful, a red, itchy bump appears where the vaccine was given. After a few days, the bump fills with fluid and begins to drain. A scab then forms. After three weeks, it falls off, leaving a small scar.