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Botulism is a rare but serious illness. Each year, U.S. healthcare providers report an average of 145 cases of botulism to the Centers for Disease Control and Prevention (CDC).

Although there are several kinds of botulism, this topic will focus on botulism caused by eating contaminated food. About 10 to 30 outbreaks of foodborne botulism are reported annually to CDC. This illness does not occur frequently, but it can be fatal if not treated quickly and properly.


Botulism is caused by toxin (poison) produced by Clostridium botulinum bacteria. This toxin affects your nerves and, if untreated, can cause paralysis and respiratory failure. C. botulinum toxin is one of the most powerful naturally occuring toxins. Exposure to the toxin, particularly in an aerosolized (spray) form, can be fatal.

C. botulinum has been made into bioweapons by rogue states and is one focus of current efforts to counter bioterrorism.


Cases of foodborne botulism often originate with home-canned foods with low acid content, such as asparagus, green beans, beets, and corn. Clostridium botulinum, the bacterium that causes botulism, thrives in sealed containers because it is anaerobic, meaning it can survive and grow with little or no oxygen. Outbreaks of botulism, however, are often from more unusual sources such as baked potatoes wrapped in aluminum foil but not kept hot, and tomatoes.


Symptoms of foodborne botulism include

  • Double vision and drooping eyelids
  • Slurred speech
  • Dry mouth and difficulty swallowing
  • Weak muscles

Symptoms usually begin within 18 to 36 hours after you eat contaminated food, but can occur in as few as 6 hours or as long as 10 days afterward.

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A healthcare provider can use laboratory tests to identify C. botulinum toxin in your blood or stool if you are infected.


If you are diagnosed with botulism early, your healthcare provider can treat you successfully with an antitoxin that blocks the action of the bacterial toxin circulating in your blood. Although antitoxin keeps the disease from becoming worse, it will still take many weeks before you recover.

Your healthcare provider may try to remove any contaminated food still in your gut by making you vomit or by giving you an enema.


To prevent getting foodborne botulism you should

  • Follow strict hygienic steps when canning foods at home
  • Refrigerate oils containing garlic or herbs
  • Keep baked potatoes wrapped in aluminum foil either hot until served or refrigerated
  • Consider boiling home-canned food before eating it to kill any bacteria lurking in the food


If left untreated, botulism can temporarily paralyze your arms, legs, trunk, and the muscles that help you breathe. The paralysis usually improves slowly over several weeks. People who develop severe botulism experience breathing failure and paralysis and need to be put on ventilators (breathing machines).


Basic research is helping scientists to better understand how microbes (germs) spread by contaminated food or water cause disease in humans.

NIAID-supported researchers are studying the genes that help harmful bacteria to establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation and may contribute to the development of diarrhea.

Other NIAID-sponsored research focuses on understanding more about how bacteria grow and interact in cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human and respond by activating a particular set of powerful genes that enable the bacteria to multiply in the body and cause disease.

NIAID-sponsored studies are also in progress to discover new ways to prevent infection and treat people suffering from progressing disease.​

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Last Updated August 19, 2010

Last Reviewed August 19, 2010