Smallpox
Basic Facts
- Scientific name: Variola major;a virus from the Orthopoxvirus family
- A closely related virus, Variola minor,causes a less severe form of illness with less than 1 percent fatality rate.
- Smallpox was a naturally occurring disease that killed an estimated 300 million people in the 20th century.
- Officially eradicated in nature in 1980, smallpox has more recently been of concern as a potential bioterrorism threat.
- The smallpox virus is moderately contagious; direct, face-to-face contact is usually required to spread the disease. Smallpox can also be spread through direct contact with infected body fluids or contaminated objects (e.g., bedding).
- Characterized by skin lesions and high fever, smallpox historically has killed approximately 30 percent of those infected.
- Routine vaccinations in the United States ended in 1972. At present, a large portion of the population is considered vulnerable to infection should a bioterrorism incident occur.
Smallpox as a Weapon
Because it is contagious from person to person and could potentially infect large groups of people, taxing the healthcare systems of a community, smallpox would be an attractive weapon for terrorists. It would most likely be delivered in an aerosol form.
- The smallpox virus could be disseminated into the air as a fine spray or powder and could infect large numbers of people.
- In aerosol form, the smallpox virus may be infectious for 24 hours before degrading. Heat and sunlight (UV exposure) may destroy the virus within hours.
- Terrorists could possibly use smallpox virus samples to intentionally infect a few people, possibly themselves, with the intention of infecting others. However, it is doubtful that any one individual would succeed in infecting more than a few others. By the time that these individuals were contagious, they would be very obviously seriously ill.
What We Don't Know About Smallpox as a Weapon
Experts do not know if the smallpox virus in a weaponized form would be as contagious as the disease was before it was eradicated.
Identifying an Attack
Because smallpox has been eradicated worldwide, even one case of smallpox would be considered a probable terrorist attack.
The first sign of an attack would most likely be victims becoming ill, usually between seven and 17 days after exposure.
A properly disseminated aerosol cloud of the smallpox virus would be invisible, odorless, and extremely hard to detect.
Smallpox Illness
Exposure:
- The incubation period is typically seven to 17 days following exposure.
- Infection usually occurs only when a susceptible person is in face-to-face contact with someone who has the virus and is ill with fever and a rash of round lesions.
- The virus is usually spread by droplets; however, having it spread by aerosol or contaminated objects (e.g., bedding) is also possible.
- Smallpox is not known to be transmitted by insects or animals.
Symptoms:
- Initial symptoms of smallpox may include high fever, fatigue, headache, and backache.
- Typically, people with smallpox are not contagious until lesions start appearing and they are obviously ill.
- Two to three days after the onset of symptoms: A rash of round lesions develops on the face, arms, and legs. At the same time, lesions in the mouth are also present and release large amounts of the virus into the saliva.
- Seven days after the onset of symptoms: The lesions become small blisters and by the seventh day are filled with pus.
- Twelve days after the onset of symptoms: Lesions begin to crust over. Severe abdominal pain and delirium can occur in the later stages of the disease.
- Three to four weeks after the onset of symptoms: Scabs develop and fall off. A patient who survives is no longer contagious after the final scab falls off.
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