Botulism

  1. What is botulism?
    Foodborne botulism occurs when a person ingests pre-formed toxin that leads to illness within a few hours to days. Foodborne botulism is a public health emergency because the contaminated food may still be available to other persons besides the patient. Infant botulism occurs in a small number of susceptible infants each year who harbor C. botulinum in their intestinal tract. Wound botulism occurs when wounds are infected with C. botulinum that secretes the toxin.
  2. Is botulism fatal?
    For the period 1899-1949, the case-fatality ratio was high at approximately 60%, but since about 1950, mortality has gradually decreased (Table 2). For the period 1950-1996, the case-fatality ratio was 15.5%. This decline in case-fatality ratio is due primarily to improvements in supportive and respiratory intensive care and perhaps to the prompt administration of antitoxin. The case-fatality ratio has generally declined over the years for all toxin types.
  3. How do I protect myself and others from exposure to botulism?
    Botulism can be prevented. Foodborne botulism has often been from home-canned foods with low acid content, such as asparagus, green beans, beets and corn. However, outbreaks of botulism from more unusual sources such as chopped garlic in oil, chile peppers, tomatoes, improperly handled baked potatoes wrapped in aluminum foil, and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminum foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, persons who eat home-canned foods should consider boiling the food for 10 minutes before eating it to ensure safety.

    Instructions on safe home canning can be obtained from county extension services or from the US Department of Agriculture. Because honey can contain spores of Clostridium botulinum and this has been a source of infection for infants, children less than 12 months old should not be fed honey. Honey is safe for persons 1 year of age and older. Wound botulism can be prevented by promptly seeking medical care for infected wounds and by not using injectable street drugs. Additional information about prevention of foodborne illnesses can be found here: CDC Foodborne Illness
  4. How is exposure to botulism treated?
    The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a breathing machine (ventilator) for weeks, plus intensive medical and nursing care. After several weeks, the paralysis slowly improves. If diagnosed early, foodborne and wound botulism can be treated with an antitoxin which blocks the action of toxin circulating in the blood. This can prevent patients from worsening, but recovery still takes many weeks. Physicians may try to remove contaminated food still in the gut by inducing vomiting or by using enemas. Wounds should be treated, usually surgically, to remove the source of the toxin-producing bacteria. Good supportive care in a hospital is the mainstay of therapy for all forms of botulism. Currently, antitoxin is not routinely given for treatment of infant botulism.
  5. What are the signs and symptoms of exposure to botulism?
    With foodborne botulism, symptoms begin within 6 hours to 2 weeks (most commonly between 12 and 36 hours) after eating toxin-containing food. Symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, muscle weakness that always descends through the body: first shoulders are affected, then upper arms, lower arms, thighs, calves, etc. Paralysis of breathing muscles can cause a person to stop breathing and die, unless assistance with breathing (mechanical ventilation) is provided.
  6. How do I determine if I was exposed to botulism?
    Physicians may consider the diagnosis if the patient's history and physical examination suggest botulism. However, these clues are usually not enough to allow a diagnosis of botulism. Other diseases such as Guillain-Barré syndrome, stroke, and myasthenia gravis can appear similar to botulism, and special tests may be needed to exclude these other conditions. These tests may include a brain scan, spinal fluid examination, nerve conduction test (electromyography, or EMG), and a tensilon test for myasthenia gravis. The most direct way to confirm the diagnosis is to demonstrate the botulinum toxin in the patient's serum or stool by injecting serum or stool into mice and looking for signs of botulism. The bacteria can also be isolated from the stool of persons with foodborne and infant botulism. These tests can be performed at some state health department laboratories and at CDC.
  7. What do I do if I suspect I was exposed to botulism?
    A health care provider should be consulted for a diarrheal illness is accompanied by high fever (temperature over 101.5 Fahrenheit, measured orally); blood in the stools, prolonged vomiting that prevents keeping liquids down (which can lead to dehydration); signs of dehydration, including a decrease in urination, a dry mouth and throat, and feeling dizzy when standing up; and diarrheal illness that lasts more than 3 days.
  8. Is botulism contagious?
    No. Botulism is not spread from one person to another.
  9. Is there a vaccine or antidote for exposure to botulism?
    A supply of antitoxin against botulism is maintained by Centers for Disease Control. The antitoxin is effective in reducing the severity of symptoms if administered early in the course of the disease. Most patients eventually recover after weeks to months of supportive care.
  10. How does exposure to botulism occur?
        In the United States an average of 110 cases of botulism are reported each year. Of these, approximately 25% are foodborne, 72% are infant botulism, and the rest are wound botulism. Outbreaks of foodborne botulism involving two or more persons occur most years and usually caused by eating contaminated home-canned foods. The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially in California.
  11. Where is botulism found?
    Foodborne botulism outbreaks have been reported from 46 states, Puerto Rico, and Washington D.C., from 1899 through 1996. Only 4 states have never reported any foodborne botulism: Delaware, New Hampshire, South Carolina, and Vermont. Five western states (California, Washington, Colorado, Oregon, and Alaska) have accounted for more than half (53.8%) of all reported foodborne outbreaks since 1950. Alaska alone accounts for 16.2% of outbreaks nationwide. This is because of the distinctive public health problem among the Alaska Native population, in which all botulism cases have been associated with improper preparation and storage of traditional Alaska Native foods. This regional distribution of outbreaks by toxin type is in keeping with the findings of a survey of soil samples which demonstrated a predominance of different types of spores in soil specimens of the northeast and central states and marine life and sediment from the Pacific Northwest and the Great Lakes.
  12. How does botulism work?
    After they are swallowed, there is a delay, called the incubation period, before the symptoms of illness begin. This delay may range from hours to days, depending on the organism, and on how many of them were swallowed. During the incubation period, the microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types of microbes stay in the intestine, some produce a toxin that is absorbed into the bloodstream, and some can directly invade the deeper body tissues. The symptoms produced depend greatly on the type of microbe. Numerous organisms cause similar symptoms, especially diarrhea, abdominal cramps, and nausea. There is so much overlap that it is rarely possible to say which microbe is likely to be causing a given illness unless laboratory tests are done to identify the microbe, or unless the illness is part of a recognized outbreak.
  13. What is the likelihood that botulism could be used?
    Botulism is generally transmitted by ingestion of toxin contaminated food. Aerosolization of the botulinum toxin has been described and may be a mechanism for bioterrorism exposure.
  14. What other risks are there for exposure to botulism?
    Botulism can result in death due to respiratory failure. However, in the past 50 years the proportion of patients with botulism who die has fallen from about 50% to 8%. A patient with severe botulism may require a breathing machine as well as intensive medical and nursing care for several months. Patients who survive an episode of botulism poisoning may have fatigue and shortness of breath for years and long-term therapy may be needed to aid recovery.
  15. Are there any historical uses or accidents involving botulism?
    In the United States an average of 110 cases of botulism are reported each year. Of these, approximately 25% are foodborne, 72% are infant botulism, and the rest are wound botulism. Outbreaks of foodborne botulism involving 2 or more persons occur most years and usually caused by eating contaminated home-canned foods. The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially in California.
  16. How can people get more information about botulism?
    People can contact the agencies listed on this page: Biological / Chemical Agent Information