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Anthrax is the disease caused by the bacterium Bacillus anthracis, which lives in soil. The bacterial cell lives as a hardy spore to survive harsh conditions. The spores germinate into thriving colonies of bacteria once inside an animal or person. Anthrax usually affects livestock far more than humans, but—as we know from the 2001 anthrax attacks in the United States—anthrax is feared as a modern biological weapon.

Forms of Anthrax

Anthrax occurs in three forms:

  1. Cutaneous (affecting the skin)
  2. Inhalational (in the lungs)
  3. Gastrointestinal (in the digestive tract)

Cutaneous Anthrax

Cutaneous anthrax is the most common form of the disease. People with cuts or open sores can get cutaneous anthrax if they come in direct contact with the bacteria or its spores, usually through contaminated animal products. The skin will redden and swell, much like an insect bite, and then develop a painless blackened lesion or ulcer that may form a brown or black scab, which is actually dead tissue. Cutaneous anthrax responds well to antibiotics but may spread throughout the body if untreated. People who work with certain animals or animal carcasses are at risk of getting this form of the disease. Cutaneous anthrax is rare in the United States.

Inhalational Anthrax

When a person inhales the spores of Bacillus anthracis, they germinate and the bacteria infect the lungs, spreading to the lymph nodes in the chest. As the bacteria grow, they produce two kinds of deadly toxins.

Symptoms usually appear 1 to 7 days after exposure, but they may first appear more than a month later. Fever, nausea, vomiting, aches, and fatigue are among the early symptoms of inhalational anthrax; it progresses to labored breathing, shock, and often death.

Historically, the mortality rate for naturally occurring inhalational anthrax has been 75 percent, even with appropriate treatment. But inhalational anthrax is rare. In the 2001 anthrax attacks, 11 people were infected with inhalational anthrax and 6 survived. Prior to 2001, the last known U.S. case was in 1976, when a California craftsman died after getting the infection from imported yarn contaminated with anthrax spores.

Gastrointestinal Anthrax

People can get gastrointestinal anthrax from eating meat contaminated with anthrax bacteria or their spores. Symptoms are stomach pain, loss of appetite, diarrhea, and fever. Antibiotic treatment can cure this form of anthrax, but left untreated, it may kill half of those who get it.

Gastrointestinal anthrax occurs naturally in warm and tropical regions of Asia, Africa, and the Middle East. It is the least common form of anthrax in the United States.

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Last Updated September 30, 2013