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Listeriosis

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What is listeriosis?

Listeriosis is an illness caused by the Listeria monocytogenes bacterium that sometimes occurs when people eat contaminated food. The bacterium is found in the environment, especially in soil, plants and water, as well as in human and animal fecal matter. It may also be present in many different types of foods, including meat, poultry, fish, seafood, raw milk and foods made from it, some cheeses, raw vegetables, and processed and ready-to-eat foods sold in retail stores, as well as deli meats (sausages, hot dogs, pâtés, etc.). The Listeria monocytogenes bacterium spreads through contact with infected matter or an infected surface during food preparation.

Listeriosis has been a reportable disease in Québec since November 2003. The number of cases reported annually has increased since monitoring began; this may be partly due to greater vigilance in the medical profession regarding diagnosis.

How is listeriosis transmitted?

Eating food contaminated with the Listeria monocytogenes bacterium is the main source of listeriosis infection in human beings. Listeriosis may also be contracted through contact with an infected animal or nosocomial transmission (during healthcare), but such cases are extremely rare. An infected mother may also transmit the disease to a foetus during pregnancy or a newborn during birth.

What are the symptoms?

Healthy individuals are rarely affected by the bacterium.

Listeriosis symptoms are generally similar to those of gastroenteritis: vomiting, nausea, abdominal cramps, diarrhea or constipation. Severe headaches and persistent fever may also occur. These unpleasant symptoms usually appear between 3 and 30 days after the person has eaten contaminated food, but may occur up to 70 days later.

How can the illness be prevented?

People are urged to take all the necessary precautions when handling, cooking and storing food. These key points are most important:

  • Throw out any products that have been recalled - do not eat them.
  • Store foods in a refrigerator at temperatures not exceeding 4oC.
    Boil or thoroughly cook all foods.
  • Do not consume raw, unpasteurized milk or foods containing it.
  • Wash raw vegetables thoroughly before eating them.
  • Wash your hands thoroughly before and after handling foods of any kind.
  • Use separate utensils for raw foods and cooked foods.
  • Pay attention to "best before" expiry dates.

For further information, consult the guide for consumers Ce lien ouvrira une nouvelle fenêtre. (French only) on the website of the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec (MAPAQ)

Who is at risk for complications?

Groups at higher risk of contracting the serious form of the illness are infants, elderly people, pregnant women, and individuals with a weakened immune system.

For people in these groups, rigorous adherence to the general precautions listed above is particularly important. They are also advised not to consume foods more likely to be contaminated with listeriosis, such as raw, unpasteurized milk and foods containing it, soft cheeses, refrigerated pâtés, refrigerated smoked fish products, deli meats, and processed and ready-to-eat foods.

What should you do if you have eaten something included in a listeriosis recall?

The risk of developing listeriosis after consuming contaminated food is very low. If you have eaten something that has been recalled and have no symptoms, we do not recommend undergoing screening tests or preventive treatment, even if you are in a high-risk group. However, if you have eaten something that is recalled and experience symptoms within two months, you should contact Info-Santé 8-1-1 or your doctor and explain about your exposure.

Is listeriosis treatable?

People with listeriosis can be given a course of antibiotics. If the infection occurs during pregnancy, prompt antibiotic treatment often prevents infection of the foetus and newborn.

For more information

Call Info-Santé 8-1-1 or visit the following websites:

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