Anthrax is an infectious disease caused by bacteria called Bacillus anthracis. Infection in humans most often involves the skin, the gastrointestinal tract, or the lungs.

See also:

• Cutaneous anthrax
• Inhalation anthrax

Anthrax commonly affects hoofed animals such as sheep and goats, but humans who come into contact with the infected animals can get sick from anthrax, too. In the past, the people who were most at risk for anthrax included farm workers, veterinarians, and tannery and wool workers.

There are three main routes of anthrax infection:

• Cutaneous anthrax occurs when anthrax touches a cut or scrape on the skin.
• Inhalation anthrax develops when anthrax spores enter the lungs.
• Gastrointestinal anthrax occurs when someone eats anthrax-tainted meat. The disease usually develops within one week, and can affect the mouth, esophagus, intestines, and colon. The infection can spread to the bloodstream, and may result in death.

Anthrax may be used as a biological weapon or for bio-terrorism. In 2001, anthrax sent through the U.S. Postal Service infected 22 people; 7 survivors had confirmed cutaneous anthrax disease.

While at least 17 nations are believed to have a biological weapons program, it is unknown how many nations or groups are working with anthrax. Most bio-terrorism experts have concluded that it is difficult to use anthrax effectively as a weapon on a large scale.

• Cutaneous anthrax: Blister or ulcer that later forms a black scab, and is usually surrounded by a lot of swelling
• Inhalation anthrax: Begins with fever, malaise, headache, cough, shortness of breath, and chest pain; shock may occur in the second stage
• Gastrointestinal anthrax: Nausea and vomiting (the vomit may include blood), anorexia, and bloody diarrhea

The tests to diagnose anthrax depend on the type of disease suspected.

• If cutaneous anthrax is suspected, you may have a culture of the skin sore to test for the bacteria that causes anthrax.
• If inhalational anthrax is suspected, you may need a chest x-ray, blood cultures, sputum cultures, spinal tap for CSF culture, or gram stain. Samples may be sent to a special lab for more testing, including PCR, immunofluorescence, and immunohistochemistry.

Most people with anthrax are treated with antibiotic therapy. Several antibiotics are effective, including penicillin, doxycycline, and ciprofloxacin (Cipro).

When treating inhalation anthrax, a combination of antibiotics should be used. Doctors often start treatment with an intravenous form of Cipro plus another drug.

Cutaneous anthrax is treated with pill (oral) antibiotics.

The length of treatment is currently about 60 days, since it may take anthrax spores that long to grow.

In the event of a bioterrorist attack, the National Pharmaceutical Stockpile is available to help provide antibiotics should a shortage occur.

When treated with antibiotics, cutaneous anthrax is likely to get better. However, up to 20% of people who do not get treatment may die due to anthrax-related blood infections.

People with second-stage inhalation anthrax have a poor outlook, even with antibiotic therapy. Up to 90% of cases in the second stage are fatal.

The prognosis of gastrointestinal anthrax is also poor. A high number of people die from this form of the disease.

• Cutaneous anthrax: Spread of infection into the bloodstream
• Inhalational anthrax: Hemorrhagic meningitis, mediastinitis, shock, and death
• Gastrointestinal anthrax: Hemorrhage, shock, and death

Call your health care provider if you have been exposed to anthrax, or if you develop symptoms of any type of anthrax.

There are two main ways to prevent anthrax.

For people who have been exposed to anthrax (but have no symptoms of the disease), doctors may prescribe preventive antibiotics, such as ciprofloxacin, penicillin, or doxycycline, depending on the strain of anthrax.

An anthrax vaccine is available to certain military personnel, but not to the general public. It is given in a series of six doses. There is no known way to spread cutaneous anthrax from person to person. People who live with someone who has cutaneous anthrax don't need antibiotics unless they have also been exposed to the same source of anthrax.

Reissman DB, Whitney EA, Taylor TH Jr, et al. One-Year Health Assessment of Adult Survivors of Bacillus anthracis Infection.JAMA. 2004;291:1994-1998.

Inglesby TV, O'Toole T, Henderson DA, et al. Anthrax as a Biological Weapon, 2002. JAMA.160;2002;287:2236-2252.