Anthrax is caused by the rod-shaped bacterium Bacillus anthracis. Like most bacteria, it reproduces by forming spores. It is primarily a disease of hoofed animals like cattle, sheep, and goats. But it can affect humans, too. Farmers, veterinarians, and workers in the tannery and wool industries have been the people most likely to get anthrax. Anthrax has also been used as a biological warfare weapon. A person can get anthrax by breathing in the spores (inhalation anthrax), by getting the bacteria through a cut in the skin (cutaneous anthrax), or by eating food contaminated with it (intestinal anthrax). It is not a contagious disease. It can't be passed from person to person.

Anthrax is an ancient disease. Biblical scholars believe that the fifth plague of Egypt (pestilence on livestock) was animal anthrax and that the sixth plague (skin boils) was cutaneous anthrax. By the 16th century, doctors were accurately diagnosing anthrax. In the 1870s, scientist Robert Koch linked anthrax to B. anthracis, the first bacterium clearly linked to a disease. (Koch went on to discover the bacteria that cause tuberculosis and cholera.) Cases of anthrax have been reported all over the world. It occurs only every now and then in the U.S. Most cases come from infected cattle.

If a person has been exposed to anthrax, but has no symptoms, the CDC recommends that doxycycline, ciprofloxacin, or levofloxacin be prescribed. The person might also need to be immunized against anthrax if the exposure was to potentially airborne B. anthracis spores.

The longer spores last, the more likely it is that the bacteria will survive. Anthrax spores can survive for more than 50 years in dry soil, such as that found in the Midwest and Southwest. Anthrax spores also can survive for long periods inside buildings and on equipment. The spores are very hard to kill with standard disinfectants and sterilization. So it’s nearly impossible to clean up contaminated equipment and buildings. Some contaminated buildings have been taken apart. Some parts have been burned up, and the rest buried.

The largest human anthrax outbreak ever reported occurred in Zimbabwe during a civil war. In the outbreak, 9,445 cases were reported and 141 people died. Most of the cases were cutaneous (skin) anthrax, rather than inhalation or intestinal anthrax. This occurred because of the butchering, eating, and disposing of cattle that had died of anthrax.

With treatment, cutaneous anthrax is not fatal. Although 20% might seem high, a person with the inhaled form of anthrax is almost certain to die without treatment.

A building contaminated by anthrax spores is extremely difficult to clean up. The CDC successfully cleaned up the Hart Building in Washington, D.C., with chlorine dioxide gas. This gas had worked well bacteria closely related to anthrax. But until the Hart Building, it was unknown whether it would work on anthrax spores spread throughout a building.

The first anthrax vaccine was developed in 1881 by the French microbiologist Louis Pasteur. Although microbiology was a relative new science, Pasteur was able to make an effective vaccine even with limited tools. Vaccine work on anthrax has continued. In the U.S., a live organism vaccine (the Sterne vaccine) is available for animals. A safe and effective antitoxin vaccine is available for people. Currently, only U.S. military personnel are immunized against anthrax. If anthrax becomes a significant problem, U.S. civilians can be immunized.

The vaccine used by the U.S. military appears to have no long-term complications. Some recruits have refused to be vaccinated, and others have reported post-vaccination problems. But no consistent complaint has been linked to vaccination. The anthrax vaccine is given as a series of 6 injections. After the first injection, 2 others are given, 2 and 4 weeks later. Boosters are then given at 6, 12, and 18 months. It takes 18 months to become fully immune, although immunity begins building after the first injection.