What is it

Smallpox is a deadly disease caused by a virus known as variola, a Latin word meaning "speckled." The virus, which can cause red lesions and pustules on the skin, is spread most often by an infected person releasing saliva droplets from their mouth into the air. Those droplets are then inhaled by a susceptible person in close contact with the ill person. Contamination is also possible through bed linens and clothing. People are most infectious from during the first week of the illness, but the disease can still be transmitted to others through scabs that have separated from the skin. It is not known to be spread by animals or insects.

Outbreaks involve either variola minor or the more deadly variola major. Those suffering from variola major become bedridden during the eruption of the rash and remain so throughout the illness. Spread of infection is limited to close contacts. Variola minor, however, can be so mild that patients can remain ambulatory during the infectious phase of their illness and thus spread the virus far more widely.

Smallpox likely was first used as a biological weapon during the French and Indian Wars. British soldiers distributed blankets that had been used by smallpox patients to initiate outbreaks among American Indians. Epidemics occurred, killing more than 50 percent of many affected tribes.

Smallpox was eradicated in 1977. In 1980, the World Health Assembly recommended that all countries cease vaccination and that all laboratories destroy their stocks of the virus or transfer them to one of two World Health Organization reference labs. All countries reported compliance.

Syntoms

The incubation period is seven to 17 days following exposure. Symptoms include high fever, fatigue, headaches and backaches, which are followed by a rash with lesions that develops within two to three days on mostly the face, arms and legs. Those lesions are round, tense and deeply embedded in the skin. They fill with pus and begin to crust early in the second week of the rash. Scabs eventually develop and fall off after three to four weeks. Lesions in the mouth and throat that appear early in the illness ulcerate and release large amounts of the virus in saliva. Severe abdominal pain and delirium are other symptoms that are sometimes present.

Testing

In some instances, the virus can be detected in swabs taken from the pharynx five to six days before the rash develops. The disease is commonly identified by the distinctive rash it causes on the face, hands and other readily visible portions of the body.

Recovery Potential

The majority of patients with smallpox recover, but death occurs in up to 30 percent of the cases. Most of those deaths occurred during the first or second week of illness. Sixty-five percent to 80 percent of survivors are marked with deep-pitted scars. Blindness is another possible complication for survivors of smallpox.

Prevention/Treatment

The vaccine against smallpox is a live virus vaccine that contains a related virus called vaccinia virus that provides immunity against infection. The vaccine does not contain the smallpox virus. If the vaccine is given within four days after exposure to smallpox, it can lessen the severity of the illness or even prevent it.

Routine vaccination against smallpox ended in 1972. The level of immunity, if any, among those who were vaccinated before 1972 is uncertain. Prior infection with the disease provides lifelong immunity.

Patients with smallpox could benefit from supportive therapy, such as intravenous fluids and medicine to control fever or pain, and antibiotics for secondary bacterial infections.

Environmental Cleanup

Symptomatic patients are placed in medical isolation so that they will not continue to spread the virus. In addition, people who have come into close contact with smallpox patients should be vaccinated immediately and closely watched for symptoms. Vaccine and isolation are the strategies for stopping the spread of smallpox.

Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Contaminated surfaces are cleaned with disinfectants such as bleach and quaternary ammonia, which has additional surfactant (detergent) action that removes excess mucus containing parasites and bacteria. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water.

Various agencies are currently validating tests designed to test for the smallpox virus in the environment. In the event of an aerosol release of smallpox, all viruses will be inactivated or dissipated within one to two days. Therefore, buildings exposed to the initial aerosol release of the virus do not need to be decontaminated. By the time the first cases are identified, typically two weeks after the release, the virus in the building will be gone.

Suspected cases of smallpox or suspected intentional release of smallpox should be reported to a local health department, which is responsible for notifying the state health department, the FBI and local law enforcement. The state health department will notify the CDC.