Listeriosis

Listeriosis is an illness caused by eating food contaminated with the bacteria Listeria monocytogenes. Some foods have a higher risk of being contaminated with Listeria.

For most people, the risk is low. However, the infection can be serious in some people at risk. These people should avoid certain foods in order to reduce the risk of infection. For more information about foods that people at risk should avoid, go to the Foods likely to be contaminated with Listeria section.

Listeria monocytogenes bacteria are found naturally in the environment, for example in soil, vegetation, water and the feces of some animals. They can contaminate food and cause disease in humans and animals. To find out more about listeriosis in animals, go to the Listeriosis in animals page.

People with listeriosis may have various symptoms. The most frequent symptoms of listiriosis are the following:

• Fever
• Muscle pain
• Nausea
• Vomiting
• Diarrhea or constipation
• Headache

Most often, symptoms manifest themselves 3 to 30 days after eating contaminated food. However, symptoms can sometimes appear even up to 70 days after. Pregnant women may experience symptoms similar to seasonal flu.

Listeriosis is treated with antibiotics.

Listeriosis may cause encephalitis or meningitis in people at risk. Bacteria can also enter the blood and cause blood poisoning.

In pregnant women, listeriosis can lead to premature birth or abortion.

Listeriosis is contracted by eating foods contaminated with the bacterium Listeria monocytogenes.

The infection can also be transmitted to the foetus or newborn.

Foods likely to be contaminated with Listeria

The Listeria monocytogenes bacterium can be found in the following food products:

• Meat eaten raw, tartar for example
• Raw fish, eaten in tartar or sushi, sashimi and maki
• Products made from raw or unpasteurized milk
• Prepared foods that may have been contaminated during processing (after the cooking and before packaging), including:
  • Ready-to-eat products
  • Smoked fish, such as salmon
  • Soft and semi-soft cheeses made from pasteurized milk
  • Cooked meat products such as pâtés, terrines, rillettes, and fermented sausages
  • Hot dog sausages
• Fresh produce, pre-packaged salads and cantaloupes for example

Cooking kills the listeriosis bacterium.

The bacterium can also multiply in cold temperatures (4 ° to 10 °C), in food stored in the fridge for example.

Lastly, Listeria contamination can occur from handling products (cross-contamination), i.e. direct contact of healthy products with contaminated ones.

It is generally recommended that you avoid eating foods likely to be contaminated with Listeria, especially for people at risk.

When handling food, you must take certain precautions at every step, from cooking to preservation.

Have good habits for washing and handling food

Here are some tips for washing and handling food properly: 

• Rinse fruits and vegetables (even those that must be peeled) before eating them raw, chopping or cooking them
• Use a small brush to wash well fruits and vegetables eaten or served with skin (melons, squash, and cucumbers for example)
• Dry washed food with a clean, dry cloth or paper towel
• Always separate raw meat from vegetables, as well as from cooked and ready-to-eat products
• Use separate utensils to handle raw and cooked foods

Keep a clean area

Here are some tips for keeping your environment clean: 

• Wash your hands, and wash knives, counters and cutting boards after use and after handling raw meat
• Promptly clean any liquid dripping in the refrigerator (liquid from sausages, hot dogs, or chicken packages, etc.)

Adopt safe food consumption habits

Here are some good habits for safe food consumption:

• Throw away or avoid consuming foods that have been recalled
• Respect cooking recommendations
• Observe ‘best before’ dates
• Cook raw foods thoroughly, especially meat and seafood
• Keep food in the fridge at a temperature of 4 °C or less
• See how to handle food on the handle food precautions
• For keeping food, see the Safe storage tips page
• For preserving the quality of the food you buy and prepare, see the food safety at home section

People in good health are rarely affected by the bacterium. Risk of listeriosis is weak in these people, even if they eat a contaminated food.

People most at risk of contracting listeriosis include:

• Pregnant women
• Seniors
• People with a weak immune system

Consumption of food subject to a recall due to Listeria

A recall is a warning published about a food when the consumption of it is considered to be dangerous to health. Even when someone has eaten contaminated food, risk of listeriosis is very low. If you have eaten a recalled item and show symptoms within 2 months, contact Info-Santé 811 or your doctor.

To know the list of recalled foods, visit the websites of the ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec (MAPAQ) (in French only) or the Canadian Food Inspection Agency.

Reportable disease

Listeriosis has been a reportable disease in Québec since November 2003. Laboratories and doctors that receive sample results from infected individuals must report all cases of listeriosis to public health authorities for tracking.