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Clostridium botulinum spores stained with malachite green stain


What is Botulism and how do people get it?

Botulism is a serious illness that causes paralysis or muscle weakness, including weakness in muscles needed for breathing. It is caused by a poisonous nerve toxin released by bacteria named Clostridium botulinum.


Most of the time, botulism bacteria live in an inactive form called spores. Inactive botulism spores are found widely in soil, dust, and honey. A hard coating helps the spores survive heat, drying, and radiation for long periods of time. When botulism spores enter the human body, they turn into active botulism bacteria and begin making botulism nerve toxin. Botulism toxin can also be present in foods that are not properly canned or refrigerated.


Botulism is not a common illness but it does occur naturally. In 2004-2005 there 11 cases of botulism in San Francisco. Naturally-occurring botulism can occur when:

  • An infant under 12 months old swallows raw honey or corn syrum contaminated with botulism spores (infant botulism). Raw honey and corn syrup are not a danger to older children or adults, just to infants.
  • Someone injects heroin that has been contaminated with botulism spores (wound botulism). "Black tar" heroin is most frequently associated with wound botulism.
  • A person eats food containing botulism toxin (food-borne botulism).


Terrorists could use botulism to hurt people on purpose by releasing botulism toxin in public places. This would cause people to breathe in the toxin or to swallow it after it gets on their hands or their food.


What if there is a Botulism Emergency in San Francisco?

The San Francisco Department of Public Health (SFDPH) has a plan to respond quickly to a botulism emergency. SFDPH will evaluate the botulism situation and may recommend ways for people to keep themselves and their family safe. SFDPH will also participate in efforts to provide needed medical support and treatment, and to reduce any ongoing sources of botulism toxin.

How can I keep from getting Botulism?

To lower your risk of getting botulism from a natural source:

  • Store food at the correct temperature. For example, refrigerate food at all times if the package says "Refrigerate" or "Perishable" or if it was refrigerated at the store. Potatoes baked in aluminum foil must either be kept hot or refrigerated.
  • Discard foods after the expiration date or if a food can is swollen, rusty, or damaged.
  • Follow strict hygienic procedures when you do home canning. Boil home-canned foods for 10 minutes before eating.
  • Do not give infants younger than 12 months honey, corn syrup, or undercooked foods.
  • Never inject street drugs, especially black tar heroin. It is not possible to prevent wound botulism by cooking or cleaning the dope. If you must inject, use new sterile syringes for each injection. If you must reuse, clean syringes with bleach. Before injecting, thoroughly clean the injection site with soap and hot water or with alcohol swabs. Never share needles, syringes, or works.


To lower your risk of getting sick if terrorists release botulism toxin on purpose:

  • If you were exposed to a suspicious substance or if you were in an area thought to contain botulism toxin, it may help to wash your skin and hair thoroughly with soap and water. It may also help to change and wash your clothing, or if you cannot wash your clothes immediately, to put them in a plastic bag to keep them separate from your other things.

Can Medicine or a Vaccine (shot) Prevent Botulism?

No. There is no medicine to prevent botulism. There is an investigational vaccine that is available only to laboratory people working with Clostridium botulinum or the toxin.

Can I catch botulism from Someone?

No. Botulism is not contagious (not spread from person to person).

What are the Signs of Botulism?

The signs of botulism disease are:

  • Drooping eyelids, seeing double, or blurry vision
  • Dry mouth, slurred speech, or trouble talking
  • Trouble breathing
  • Muscle weakness or paralysis
  • Severe constipation

After swallowing, touching, or breathing in botulism toxin, illness usually starts within 12-72 hours.  After swallowing or injecting botulism spores, it takes 4 to 14 days until the first signs of illness.


See a doctor right away if you are having the signs listed above and you think you may have been exposed to botulism. It is important to start medical treatment as soon as possible.

Is there Treatment for Botulism?

Medical treatment is available for people who are sick with botulism. Treatment may include a medicine (antitoxin) and a breathing machine (ventilator). Wound botulism may require cleaning and removal of wounds or abscesses. A breathing machine may be needed when botulism weakens the muscles needed for breathing or stops them from working altogether. Antitoxin medicine can inactivate botulism toxin, but it does not cure the disease immediately. Paralysis may take weeks or months to wear off. The supply of the antitoxin medicine may be limited in an emergency situation.


How can I find Information during a Botulism Emergency?

Check the SFDPH website Local media such as newspapers, TV stations and radio will carry emergency instructions. Emergency radio stations include: KCBS 740 AM and KGO 810 AM.


What can I do Now if I am worried about Botulism?

  • Read about botulism at and at the CDC page
  • Go to to learn about steps you can take now to prepare for all disasters.
  • Keep a card in your wallet with a list of your health problems, the names and doses of medicines you take, and any medications you are allergic to.

Additional Information


Frequently asked questions (FAQ) about Botulism


Information for health care providers

Other Links

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