Smallpox is caused by variola virus. Smallpox infection was eliminated from the world in 1977.

What are the symptoms of smallpox?

The incubation period is about 12 days (range: 7 to 17 days) following exposure. Initial symptoms include high fever, fatigue, and head and backaches. A characteristic rash, most prominent on the face, arms, and legs, follows in 2-3 days. The rash starts with flat red lesions that evolve at the same rate. Lesions become pus-filled and begin to crust early in the second week. Scabs develop and then separate and fall off after about 3-4 weeks.

What is the mortality rate for smallpox?

The majority of patients with smallpox recover, but death occurs in up to 30% of cases.

How is smallpox spread?

Smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. Persons with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off.

Is it possible to be vaccinated against smallpox?

Routine vaccination against smallpox ended in 1972. The level of immunity, if any, among persons who were vaccinated before 1972 is uncertain; therefore, these persons are assumed to be susceptible. Vaccination against smallpox is not recommended to prevent the disease in the general public and therefore is not available. In people exposed to smallpox, the vaccine can lessen the severity of or even prevent illness if given within 4 days after exposure. Vaccine against smallpox contains another live virus called vaccinia. The vaccine does not contain smallpox virus.

The United States currently has an emergency supply of smallpox vaccine.

What is the treatment for smallpox?

There is no proven treatment for smallpox but research to evaluate new antiviral agents is ongoing. Patients with smallpox can benefit from supportive therapy (intravenous fluids, medicine to control fever or pain, etc.) and antibiotics for any secondary bacterial infections that occur. There is a specific medication called immunoglobulin that can be used after exposure to smallpox. This is available through the CDC. Stores of smallpox vaccines do exist at the CDC and these stores are growing in number.

What sort of isolation is required for smallpox?

Those caring for patients diagnosed with smallpox should follow Strict Airborne Precautions with the use of the N95 respiratory mask instead of the regular mask that is used with other respiratory diseases.

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