Listeria (Listeriosis)

What is Listeriosis foodborne illness?

Listeriosis (lis-tir-e-O-sis) is a well recognized type of “food poisoning” or “foodborne disease”, caused by Listeria monocytogenes (lis-TIR-ee-ya mon-o-si-TAH-gineez) bacteria.

What are the symptoms?

This infection can cause:

  • fever
  • muscle aches
  • diarrhea
  • nausea
  • headache
  • stiff neck
  • confusion
  • loss of balance
  • and convulsions.

Symptoms can begin three to 70 days after ingesting the bacteria, but most often begin around three weeks. The elderly, infants, pregnant women, and those with chronic health conditions are at higher risk of becoming infected with Listeria. Mothers can pass the bacteria to their unborn baby through the placenta, even before feeling ill. This can lead to miscarriage, stillbirth, premature birth, or serious health problems for the baby. People infected with the bacteria may pass it in their feces and urine for several months. Some people can become carriers of this bacteria, without showing any signs or symptoms of the illness.

How do I know if I have this illness?

If you have the above symptoms, you should see your family doctor, who can arrange to have your stool sample tested. If you think food may have made you sick, call one of the offices listed below.

How does it spread?

The bacteria can be found in soil, water and animals. People can get the bacteria by:

  • consuming food or water that may have come into contact with the bacteria, like:
    • food or water that has come into contact with
    • animal feces
    • undercooked meat, poultry and eggs
    • raw (non-pasteurized) milk
    • foods that have come into contact with dirty surfaces (unwashed cutting boards)
    • unwashed fruits and vegetables, eaten raw
    • processed foods that have become contaminated before packaging.

How is it treated?

Listeriosis is often treated with antibiotics. In most cases, the antibiotics also prevent infection of the fetus or newborn. People with diarrhea must drink plenty of fluids to prevent dehydration.

How can I keep from getting this illness?

Those at higher risk of illness, noted above, should:

  • Avoid eating hot dogs, luncheon meats, or deli meats unless they are reheated until steaming hot.
  • Avoid eating soft cheeses such as feta, brie, Camembert, blue-veined cheeses, or Mexican-style cheeses, unless the label says they are made from pasteurized milk.
  • Avoid eating refrigerated pâtés or meat spreads.
  • Canned pâtés or meat spreads may be eaten.
  • Avoid eating refrigerated smoked seafood unless it is an ingredient in a cooked dish. Canned fish may be eaten.

How soon can I return to work after being sick?

Usually, you can return to work as soon as you feel well, but certain jobs are more likely to allow the spread of bacteria from workers to clients. For this reason, food handlers, health care workers, and child care providers must stay off work until they are cleared by the Medical Officer of Health.

How can I avoid foodborne illnesses?

Most foodborne illness can be avoided by following these simple food safety tips:


Wash your hands frequently with soap and water:

  • Before handling food or eating.
  • After handling raw meats, using the toilet, touching pets/animals and changing diapers.

Wash counters, utensils, cutting boards, and other surfaces after they come into contact with raw meat. Don’t forget to sanitize!


  • Cook all meats, poultry, and eggs to a proper internal temperature.
  • Keep all hot foods at 60°C (140°F) or more, to prevent the growth of bacteria.
  • Use a kitchen thermometer to check cooking and storage temperatures.


  • Chill all leftovers promptly to keep them out of room temperature.
  • Refrigerate all perishable foods at 4°C (40°F) or less, to prevent the growth of bacteria.
  • Thaw frozen foods in a refrigerator, cold water, or a microwave oven, not at room temperature.


  • Use separate cutting boards for raw meats, and raw fruits and vegetables.
  • Store raw meats below ready to eat foods in the refrigerator to prevent meat juices from contaminating food you may directly consume.

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Last updated: 2019-08-14