What is anthrax?
Anthrax is a serious, sometimes deadly disease caused by infection with anthrax bacteria. These bacteria produce spores that can spread the infection.
Anthrax in humans is rare unless the spores are spread on purpose. It became a concern in the United States in 2001, when 22 cases occurred as a result of bioterrorism. Most of those cases affected postal workers and media employees who were exposed to spores when handling mail.
Most cases of anthrax occur in livestock, such as cattle, horses, sheep, and goats. Anthrax spores in the soil can infect animals who eat plants growing in the soil. People can be exposed to spores in infected animal products or meat. This is not much of a concern in North America, because livestock are vaccinated against anthrax. But people can get anthrax from handling animal skins or products made out of animal skins from parts of the world where anthrax is more common.
What causes it?
Anthrax is caused by Bacillus anthracis bacteria. There are three types of infection:
- Cutaneous (skin) anthrax.
This can occur when spores enter your body through a break in the skin. Half of the cases in the 2001 U.S. terrorist attacks were this type.
- Inhalational (lung) anthrax.
This can occur when you breathe in spores. It is the most serious type of infection. Half of the cases in the 2001 attacks were this type.
- Gastrointestinal (digestive) anthrax.
This can occur when you eat food contaminated with anthrax spores. This has occurred in developing regions of Asia, the Middle East, and Africa, but not in North America.
The illness does not seem to spread from person to person. People who come in contact with someone who has anthrax don't need to be immunized or treated unless they were exposed to the same source of infection.
What are the symptoms?
The symptoms and the incubation period—the time from exposure to anthrax until symptoms start—depend on the type of anthrax infection you have.
With cutaneous anthrax, symptoms usually appear 5 to 7 days after exposure to spores, though it may take longer.
- The first symptom may be a small, raised bump that might itch.
- The bump becomes a painless, fluid-filled blister and later forms a black center of dying tissue.
- Swollen lymph nodes, headache, and fever also may occur.
With inhalational anthrax, symptoms usually appear 1 to 7 days after exposure. (But it can take as long as 60 days).
- At first you may feel like you have the flu, with a sore throat, a mild fever, and muscle aches. But you may also have shortness of breath, which is not common with the flu.
- Severe trouble breathing, high fever, and shock may occur 1 to 5 days later.
- Death usually follows within a day or two.
With gastrointestinal anthrax, symptoms usually occur within a week after exposure.
- At first you may have mouth ulcers, a sore throat, trouble swallowing, loss of appetite, vomiting, or a fever.
- As the illness gets worse, you may have trouble breathing (because of swelling in the throat), bloody diarrhea or vomit, or belly pain caused by fluid buildup.
How is it diagnosed?
Your doctor will ask you questions about your symptoms and about any work or other activities that may have put you at risk for exposure. If the doctor suspects you may have been exposed to anthrax, testing will be done to confirm exposure or infection. Public health officials also will be notified about a possible anthrax infection.
Anthrax is confirmed when the bacteria are identified from a culture of your blood, spinal fluid, skin sores, or mucus from your nose, airways, or lungs. If results of a culture aren't clear, you may need other blood tests or a polymerase chain reaction (PCR) test. A skin ulcer may be biopsied.
How is anthrax treated?
Antibiotics and antitoxins are used to treat all types of anthrax.
Anyone who is infected needs to be treated as soon as possible. Starting treatment before symptoms begin may make the illness less severe and prevent death. Treatment may also include supportive care in the hospital.
Anyone who has been exposed to anthrax spores but is not yet sick should be treated with antibiotics and a few doses of the vaccine to prevent infection. Not everyone who has been exposed to anthrax will get sick. But because there's no way to know who will get sick and who won't, anyone who is directly exposed will get treatment. If you think that you have been exposed, call your local law enforcement agency and your doctor right away. Don't take antibiotics without talking to your doctor first.
How can you prevent it?
In the U.S., the anthrax vaccine is used to protect only the small number of people who are at higher risk for exposure. These include:
- Some military personnel.
- Some lab workers.
- Some people who come in contact with animals from other countries.
The vaccine is not available to the general public at this time. The risk of exposure to anthrax is extremely low.
The bioterrorism attacks in 2001 made many people nervous about opening their mail. If you receive a piece of mail that contains a powdery substance or seems suspicious, the U.S. Centers for Disease Control and Prevention (CDC) recommends that you put down the piece of mail and not touch it again. Then, leave the room, wash your hands with soap and water, and call 911 to find out what to do next.
If you have concerns about anthrax, you can find the most current information through the CDC (www.cdc.gov/anthrax).
Current as of: March 9, 2022
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine
Leslie Tengelsen PhD, DVM - Zoonotic Disease