


What's the Problem?

Anthrax is an acute infectious disease caused by a bacterium, Bacillus anthracis. Anthrax is most commonly seen in hoofed animals but can also infect humans. In humans, the most serious forms of the disease are inhalation, cutaneous, and gastrointestinal. Symptoms vary depending upon how the disease was contracted but generally occur within 7 days of exposure. In a small number of cases, the spores can remain dormant in the body and then activate and produce disease weeks later.

  • Cutaneous anthrax is the most common naturally occurring type of the infection and usually occurs after skin contact with a contaminated object. Most skin infections occur when the bacterium enters through a cut or abrasion on the skin. Skin infections begin as a raised lesion that is usually painless, but patients may also experience fever, malaise, headache, and swollen lymph glands. About 20% of untreated cases of cutaneous anthrax are lethal. With appropriate antimicrobial therapy, deaths are rare.
  • Inhalational anthrax is the most lethal form of the disease. It resembles a viral respiratory illness with initial symptoms including: sore throat, mild fever, muscle aches, and malaise. Early forms of inhalational anthrax may be misdiagnosed as the flu. If untreated, symptoms will progress to respiratory failure and shock often accompanied by severe bleeding in the chest cavity (mediastinum) often resulting in death. The mediastinal involvement produces a very characteristic appearance on chest x-ray known as mediastinal widening. Even with appropriate treatment using antibiotics, the fatality rate is approximately 75%.
  • Gastrointestinal anthrax generally occurs after consuming raw or undercooked contaminated meat. Symptoms include severe abdominal distress followed by fever and septicemia. Gastrointestinal anthrax may also result in nausea, loss of appetite, vomiting, and bloody diarrhea. The fatality rate is between 25 to 60%; the impact of treatment with antibiotics is not known.


Who's at Risk?

In the U.S., the risk of contracting anthrax is extremely low. The intentional release of anthrax following the events of 9/ll resulted in only 22 recognized cases of cutaneous and inhalational anthrax. Any risk for inhalational anthrax due to cross-contaminated mail is also very low, even for postal workers. The possibility does exist, however, that if anthrax were dispersed in a public place, a large number of people could be affected.

Can It Be Prevented?

Identifying a patient with anthrax or confirming exposure to B. anthracis warrants an immediate epidemiologic investigation. The highest priority should be given to identifying at-risk individuals and determining the source of infection.

  • In the event of intentional anthrax distribution, people at risk for inhalational anthrax should take a 60-day course of prophylactic antibiotics, either doxycycline or ciprofloxacin. Amoxicillin is often given to pregnant women and children.
  • Anthrax is definitively diagnosed by isolating B. anthracis from the infected person or through other diagnostic tests.
  • Anthrax is not contagious. It cannot be spread from person to person.
  • An anthrax vaccine can prevent infection. This vaccine is not recommended for or available to the general public. It can be used if an exposure has occurred and is thought to provide additive protection from disease when used in combination with antibiotics. If used, the vaccine shortens the amount of time antibiotics are given.

The Bottom Line

Since the risk of naturally contracting anthrax in the U.S. is very low, the identification of a case should also prompt an investigation into the possibility of bioterrorism. The intentional release of a biological agent, like anthrax, constitutes an act of bioterrorism. If a person thinks they have been exposed to a biological incident or they suspect a biological threat is planned, they should contact their local health department and/or their local police department. Either of these agencies will promptly notify the FBI, which is responsible for coordinating interagency investigation of bioterrorism.

Case Example

A postal worker presents in the emergency room suffering from symptoms that include confusion, memory loss, fatigue, joint pain, and labored breathing. The physician is immediately alerted to the possibility of anthrax infection. The patient claims that it's not possible. Diagnostic testing is conducted and is, in fact, negative for anthrax. The patient was right. When the doctor carefully questions the patient, particularly regarding his certainty that he did not have anthrax infection, the patient reveals that he had put himself on a course of ciprofloxacin in order to prevent any possible infection. He ordered the drug over the Internet. After the doctor explains the risk of ordering drugs over the Internet, particularly without guidance from a physician, she goes on to explain that all the symptoms the patient has been experiencing are known side effects of ciprofloxacin. The patient discontinues taking the medication and his symptoms resolve.

  • Page last reviewed: February 2, 2011
  • Page last updated: February 2, 2011
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