NOVA Online | Bioterror

While highly infectious, smallpox carries clear signs that may prevent the spread of an epidemic.

Agents of Bioterror
Smallpox

incubation period | symptoms | how it would spread | treatment | vaccine

Through natural epidemics, smallpox has likely claimed more lives than any other infectious disease. In the 20th century alone, before it was eradicated by universal vaccination, smallpox killed up to 500 million people.

In 1980, the same year that the World Health Assembly announced smallpox had been eradicated and recommended that vaccination programs cease, the Soviet Union launched a program to mass-produce the virus as a bioweapon. Russia may still maintain a research program to produce virulent and contagious strains, ostensibly as a defensive measure.

The only confirmed repositories of smallpox are at the Centers for Disease Control and Prevention in Washington D.C. and at the Institute of Virus Preparations in Moscow, but Iraq and North Korea are suspected to have stocks. Smallpox has no natural reservoirs other than humans. While the chance of terrorists obtaining smallpox is remote, it is considered a grave bioterrorism threat because the disease is highly contagious and deadly. The most lethal natural form of smallpox, caused by the Variola major virus, has a fatality rate of roughly 30%.

Incubation period before symptoms
10-14 days

Symptoms

high fever
headache, backache, and vomiting
rash (pox) on the face and arms that spreads to the trunk

How it would be spread
Aerosol or person-to-person, potentially by a terrorist-"martyr." It is highly contagious. However, smallpox victims show clear signs of the disease, and anyone who came in contact with them could be vaccinated post-exposure.

Treatment
There is no current treatment against the smallpox virus. Vaccination given 3-5 days post-exposure can prevent the disease.

Vaccine
Vaccine exists but is currently not recommended for the general public. Stockpiles of vaccine are being increased. No one in the U.S. has been vaccinated since 1972, and people vaccinated before then have likely lost immunity.

Anthrax	Botulism	Cholera	Glanders

Plague	Q Fever	Smallpox	Tularemia

Chart of the 8 agents

Photo: Corbis Images

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