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Fact Sheet: Anthrax

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What is anthrax?

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis.  Anthrax most commonly occurs in wild and domestic mammalian species (cattle, sheep, goats, camels, antelope, and other herbivores), but it can also occur in humans when they are exposed to infected animals, to tissue from infected animals, or when anthrax spores are used as a bioterrorist weapon.

How common is anthrax and who can get it?

Anthrax is most common in agricultural regions where it occurs in animals, such as livestock and other herbivores such as deer and antelope. When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products. Workers who are exposed to dead animals and animal products from other countries where anthrax is more common may become infected with B. anthracis (industrial anthrax). Anthrax in animals rarely occurs in the United States

How is anthrax transmitted?

Anthrax is not known to spread from person to person. B. anthracis spores can live in the soil for many years and humans can become infected with anthrax by handling animal products from infected animals or by inhaling anthrax spores from contaminated animal products. Anthrax can also be spread by eating undercooked meat from infected animals. It is rare to find infected animals in the United States. Anthrax spores can be used as a bioterrorist weapon, as was the case in 2001, when Bacillus anthracis spores had been intentionally distributed through the postal system, causing 22 cases of anthrax, including 5 deaths.

What are the types of anthrax infection?

Anthrax can occur in three major forms: cutaneous (skin), inhalation, and gastrointestinal.

    Cutaneous: Most (about 95%) anthrax infections occur when the bacterium enters a cut or abrasion on the skin, such as when handling contaminated wool, hides, leather or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an insect bite, but within 1-2 days develops into a fluid-filled blister and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy.

    Inhalation: Initial symptoms may resemble a common cold – sore throat, mild fever, muscle aches and malaise. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is usually fatal.

    Gastrointestinal: The intestinal form of anthrax may follow the consumption of contaminated meat and is characterized by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, fever are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25% to 60% of cases.

How effective is the treatment for the various forms of anthrax?

Early treatment of cutaneous anthrax is usually curative, and early treatment of all forms is important for recovery. Likelihood of death in patients with cutaneous anthrax is about 20% without antibiotic treatment and less than 1% with it. Although case-fatality estimates for inhalation anthrax are based on incomplete information, the rate is thought to be as high as 75%, even with all possible supportive care including appropriate antibiotics. Of 11 people with inhalation anthrax related to the anthrax attack in 2001, 5 (45%) died. Estimates of the impact of the delay in postexposure prophylaxis or treatment on survival are not available. For gastrointestinal anthrax, the case-fatality rate is estimated to be 25%-60% and the effect of early antibiotic treatment on that case-fatality rate is not well understood.

What are the symptoms of anthrax?

These symptoms can occur within 7 days of infection:

  • Fever(temperature greater than 100 degrees F). The fever may be accompanied by chills or night sweats.
  • Flu-like symptoms.
  • Cough, usually a non-productive cough, chest discomfort, shortness of breath, fatigue, muscle aches
  • Sore throat, followed by difficulty swallowing, enlarged lymph nodes, headache, nausea, loss of appetite, abdominal distress, vomiting, or diarrhea
  • A sore, especially on the face, arms or hands, that starts as a raised bump and develops into a painless ulcer with a black area in the center.

Can anthrax be spread from person-to-person?

Direct person-to-person spread of anthrax has never been documented.

How is anthrax diagnosed?

Anthrax is diagnosed by isolating B. anthracis from the blood, skin lesions, or respiratory secretions or by several other tests that detect the presence of the organism

What is the treatment for anthrax?

Doctors can prescribe effective antibiotics. Specific antibiotics recommended would depend on the sensitivity of the organism. When information about sensitivity of the organism to antibiotics isn’t available yet, doxycycline and ciprofloxacin are recommended. To be most effective, treatment should be started early. If left untreated, the disease can be fatal.

Should people take preventive antibiotics?

No. There have been no illnesses or deaths from anthrax among Oregonians for decades. Public health officials do not recommend that doctors prescribe antibiotics for this purpose in the absence of evidence that exposure to anthrax has occurred. Inappropriate use of antibiotics can lead to harmful side effects and development of drug-resistant bacteria.

Is there an vaccine for anthrax?

A protective vaccine has been developed for anthrax. It is primarily given to military personnel. Otherwise, vaccination is recommended only for those at high risk of exposure, such as workers in research laboratories that handle anthrax bacteria routinely, or workers who regularly handle hides or other animal products.  CDC recommends that the vaccine could be used along with antibiotics to prevent anthrax disease from occurring after an exposure.

Are there adverse reactions to the anthrax vaccine?

Mild local reactions occur in 30% of recipients and consist of slight tenderness and redness at the injection site. A moderate local reaction can occur if the vaccine is given to anyone with a past history of anthrax infection. Severe local reactions are very infrequent and consist of extensive swelling of the forearm in addition to the local reaction. Systemic reactions occur in fewer than 0.2% of recipients and are characterized by flu-like symptoms.

Adapted from Questions and Answers about Anthrax, accessed at:
Issued by: The Oregon Public Health Division
Date: January 2013