Facts About Smallpox (CDC):
This material has been developed by the Centers for Disease Control and Prevention. Reuse or reproduction of this
material is authorized. Information updated September 2001.
Facts about Smallpox
Smallpox infection was eliminated from the world in 1977.
Smallpox is caused by variola virus. The incubation period is about 12 days (range: 7 to 17
days) following exposure. Initial symptoms include high fever, fatigue, and head and back aches.
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. The majority of patients with smallpox recover, but death occurs in up to 30% of cases.
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.
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
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.
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
Oct 16, '01
Last edit by Huganurse on Jul 1, '02