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Anthrax is the name given to an infection that is caused by the bacterium Bacillus anthracis. The bacterium is common in cattle, sheep, goats, camels, antelopes, and other plant-eating animals. Humans can also become contaminated with the anthrax bacterium. In the past, such human contamination was only associated with farmers or sheepherders, people who worked in close contact with infected animals. Now, however, the population as a whole is more at risk of anthrax infection because the organism has been used as a bioterrorist weapon and weapon of war.

The use of Bacillus anthracis as a weapon is due to the ability of the bacterium to form a structure known as a spore. The spore form is able to withstand prolonged periods of drought and conditions that would quickly kill the growing form of the microorganism. The dust-like spores are easily spread through air or liquids. Anthrax skin infections due to the entry of spores or the growing bacteria into a wound or scrapped region of skin are treatable and death from superficial infection is rare. Inhalation of the spores, however, can produce a lung infection that develops rapidly and is frequently fatal.

Anthrax is relatively rare in the United States because of widespread animal vaccination and practices used to disinfect hides or other animal products. For those in high-risk professions, such as livestock workers, veterinarians, or those in the military, an anthrax vaccine is available. The vaccine, which does not contain living bacteria, is 93% effective in protecting against infection. To provide this immunity, an individual must be given an initial course of three injections, given two weeks apart, followed by booster injections at 6, 12, and 18 months, and an annual immunization thereafter.

Approximately 30% of those who have been vaccinated against anthrax may notice mild local reactions such as a slight tenderness at the injection site. Someone who has already had anthrax might have a more severe local reaction upon vaccination. Infrequently, there may be a severe local reaction with extensive swelling of the forearm, and only a very few vaccine recipients may have a more general flu-like reaction to the shot.

Other means of preventing the spread of infection include careful handling of dead animals suspected of having the disease and providing good ventilation when processing hides, fur, wool, or hair. Additionally, anyone visiting a country where anthrax is common or where herd animals are not often vaccinated should avoid contact with livestock or animal products and avoid eating meat that has not been properly prepared and thoroughly cooked.

In 2001, the United States experienced several deliberate releases of anthrax spores through the mailing of contaminated letters. These incidents led to the call for a nationwide immunization program against a possible airborne bioterrorist release of the anthrax spores. However, whether the vaccine would provide complete protection against anthrax used as a biological weapon is, as yet, unclear.

A case of cutaneous anthrax. NMSB/Custom Medical Stock Photo. Reproduced by permission.

See also Biological warfare.



Inglesby, T. V., D. A. Henderson, J. G. Bartlett, et al. "Anthrax as a Biological Weapon: Medical and Public Health Management." Journal of the American Medical Association 281 (May 1999): 1735–1745.

Pannifer, A. D., T. Y. Wong, R. Schwarzenbacher, et al. "Crystal Structure of the Anthrax Lethal Factor." Nature 414 (November 2001): 229–233.


Centers for Disease Control and Prevention. 1600 Clifton Road, Atlanta, GA 30333. (800) 311–3435. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/anthrax_g.htm.>

Brian Hoyle


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—A molecule created by the immune system in response to the presence of an antigen (a foreign substance or particle). It marks foreign microorganisms in the body for destruction by other immune cells.


—Inflammation of the mucous membrane of the bronchial tubes of the lung that can make it difficult to breathe.


—Pertaining to the skin.


—Inflammation of the meninges; membranes covering the brain and spinal cord.


—Having to do with the lungs or respiratory system.


—A dormant form assumed by some bacteria, such as anthrax, that enable the bacterium to survive high temperatures, dryness, and lack of nourishment for long periods of time. Under proper conditions, the spore may revert to the actively multiplying form of the bacteria.

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