Listeria and Listeriosis

The food we eat in Canada is very safe, but sometimes it can carry bacteria, like Listeria monocytogenes (commonly called Listeria), that can make us sick.

What is Listeria?

Listeria is bacteria found in food, soil, plants, sewage and other places in nature. Animals and humans can carry Listeria in their intestines without knowing it.

Eating food with Listeria on it can cause a serious disease called listeriosis. While it is rare in Canada, it is very dangerous to pregnant women, older adults and people with weakened immune systems. In serious cases, listeriosis can lead to miscarriage, brain infection, blood poisoning and even death.

How do people get sick?

People can get listeriosis by eating meat, fish, dairy products, plants or vegetables contaminated with Listeria. Listeria can get on your food from the soil, water, manure-based fertilizers, and even farm animals that look healthy. You can also transfer Listeria from one food to another by not handling it properly.

What are the symptoms and treatment?

Fast fact

The mild form of listeriosis usually begins about one day after eating heavily contaminated food. For the more serious form of the disease, the incubation period is generally much longer: on average about 21 days, but can be up to 70 days after exposure.

Many people are exposed to Listeria, but only a few will actually develop listeriosis. Symptoms of "food poisoning" may start suddenly, and include:

  • vomiting
  • nausea
  • cramps
  • diarrhea
  • severe headache
  • constipation
  • persistent fever

Listeriosis can be treated with antibiotics, but early diagnosis is key, especially for people at high risk (e.g., pregnant women, older adults and people with weakened immune systems). At the moment, there is no vaccine to prevent listeriosis.

How do I avoid getting sick?

Foods that are contaminated with Listeria look, smell and taste normal. Unlike most bacteria, Listeria can survive and sometimes grow on foods being stored in the refrigerator. The good news is Listeria can be killed by cooking food properly.

These steps will help you reduce your risk of getting listeriosis and other foodborne illnesses:

  1. Check your fridge temperature. Check the temperature in your refrigerator using a thermometer to make sure it is at 4ºC (40ºF) or below. As the storage temperature increases, so does the growth of Listeria in foods. The higher the number of bacteria in foods, the greater the risk of getting sick.
  2. Clean your fridge often. Wash and disinfect your refrigerator regularly. The more often it is cleaned, the less chance that Listeria will be transferred from contaminated food and surfaces to non-contaminated foods.
  3. Use leftovers safely. Keep leftovers for a maximum of four days, preferably only 2-3 days, and reheat them to an internal temperature of 74ºC (165ºF) before eating them.
  4. Pay attention to "Best before" dates. "Best before" dates do not guarantee product safety, but they indicate how long the unopened products will retain their freshness and high quality. Once a package is opened, the "best before" date no longer applies. In general, after opening, refrigerated ready-to-eat (RTE) foods should not be stored in the refrigerator for longer than 4 days, and preferably only 2-3 days.
  5. Serve and store food quickly. Serve food right away, and refrigerate or freeze perishable food, prepared food and leftovers within two hours. Avoid letting foods sit at temperatures between 4ºC (40ºF) and 60ºC (140ºF).
  6. Cook thoroughly. Cook food completely, using a clean thermometer to measure the temperature. See Health Canada's safe internal cooking temperature chart to learn the proper way of taking measurements and to ensure that the food has been cooked to a safe internal temperature.
  7. Follow package directions. Read and follow all package labels and instructions about food preparation and storage.
  8. Separate meat from produce. Keep raw meats, poultry and seafood separate from produce and RTE foods in your shopping cart and fridge. Use a separate cutting boards for raw meats, poultry and seafood and one for washed fruits/vegetables and RTE foods.
  9. Wash your hands. Wash your hands with soap and water for at least 20 seconds before, during and after handling food, using the bathroom, changing diapers or handling pets.
  10. Wash produce. Wash fruits and vegetables well before you eat them.
  11. Defrost safely. Never defrost food at room temperature. Defrost in the refrigerator, in the microwave, or in cold water (replaced every 30 minutes).
  12. Clean before re-using. To avoid cross-contamination, clean all knives, cutting boards, thermometers and utensils that touched raw food before using them again. Change dishcloths daily, and avoid using sponges since they are hard to keep clean.
  13. Sanitize. After handling foods in the kitchen, especially raw foods like meat and fish, thoroughly clean and sanitize all surfaces used for preparing food. Use a kitchen sanitizer (following the directions on the container) or a bleach solution (5 ml household bleach to 750 ml of water), and rinse with water.

On top of these tips, high-risk people should avoid eating the following foods:

  • hot dogs, unless reheated until steaming hot
  • deli meats, unless dried and salted or heated until steaming hot
  • raw or unpasteurized dairy products, including soft and semi-soft cheese, such as Brie, Camembert and blue-veined cheese.
  • pâté and meat spreads, unless frozen, canned or shelf-stable
  • refrigerated smoked seafood and fish. Frozen smoked seafood and fish are of lower risk, with fully cooked, canned or shelf-stable being the safest alternatives.
  • raw or undercooked meat, poultry and fish

What does the Government do to protect me?

The Government of Canada works very hard to protect your health and safety:

  • We are carrying out a five-year Food and Consumer Safety Action Plan, to strengthen and modernize Canada's safety system and make sure you can have confidence in the quality and safety of the food, health and consumer products you buy.
  • We are investing $75 million more in Canada's food safety system (on top of the $113 million committed in 2008) to hire more inspectors, update lab technology, and improve communication with Canadians.
  • We are acting on the recommendations from the government-wide independent investigation into the 2008 listeriosis outbreak. Health Canada has also completed and is acting on its Lessons Learned Report.
  • Health Canada has completed its update (April 2011) of the Policy on Listeria monocytogenes in Ready-to-Eat (RTE) foods, in view of enhancing the control of Listeria in high-risk foods. The purpose of this policy is to provide guidance to stakeholders regarding verification and control, as well as regulatory oversight and compliance activities of RTE foods with respect to their potential to support the growth of Listeria monocytogenes.

In Canada, several government organizations work together every day to keep your food safe:

  • Health Canada makes food safety standards and policies to help minimize the risk of foodborne illnesses.
  • The Canadian Food Inspection Agency carries out inspections to make sure the food industry meets its food safety responsibilities.
  • The Public Health Agency of Canada conducts outbreak surveillance and studies the incidence and causes of diseases in Canada.
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