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Smallpox !smol-+p@ks

by Craig R. Pringle, BSc, PhD

Smallpox (variola) is a highly contagious, very deadly disease caused by the variola virus. The disease is now considered eliminated.

  • There have been no cases of smallpox since 1977.

  • People can acquire the infection by breathing air exhaled or coughed out by an infected person.

  • People have a fever, headache, backache, and rash, sometimes with severe abdominal pain, and they feel very ill.

  • The diagnosis is confirmed when the virus is identified in a sample taken from the rash.

  • Vaccination within the first few days of exposure can prevent the disease or limit its severity.

  • Treatment involves fluids, relief of symptoms, and treatments to maintain blood pressure and help with breathing.

The smallpox virus can exist only in people—not in animals.

There are two main forms. The severe form (variola major) is the most common and is the one of concern. The other form (variola minor) is much less common and much less severe.

Over 200 years ago, a vaccine against smallpox (the first vaccine ever) was developed. The vaccine proved very effective and was given to people throughout the world. The last case of smallpox was reported in 1977. In 1980, the World Health Organization (WHO) declared the disease eliminated and recommended stopping vaccination. Samples of the virus are kept in two high-security laboratories (one in the United States and one in Russia) in case the vaccine ever needs to be produced.

Because the vaccine’s protective effects gradually wear off, nearly all people—even those previously vaccinated—are now susceptible to smallpox (see Smallpox Vaccine). This lack of protection is a concern only because samples of the virus have been stored, and some people worry that terrorist groups could obtain the virus and release it into the population. The resulting epidemic would be devastating.

The smallpox virus spreads directly from person to person and is acquired by breathing air contaminated with droplets of moisture breathed or coughed out by an infected person. Contact with clothing or bed linens used by an infected person can also spread the disease. Smallpox usually spreads to people who have close personal contact with an infected person. A large outbreak in a school or workplace would be uncommon. The virus survives no more than 2 days in the environment— less if temperature and humidity are high.

Did You Know...

  • Nearly everyone, even people who were previously vaccinated, is now susceptible to smallpox.

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