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Listeria / Listeriosis

Listeria monocytogenes bacterium under microscope

Listeriosis is a food-borne illness commonly associated with foods such as deli meats, soft cheese (e.g., Brie) and refrigerated seafood (e.g., smoked salmon). It can be a mild illness in healthy individuals but can be very serious for people at higher risk such as pregnant women, those with weakened immune systems and seniors. In pregnant women, it can be serious for the unborn child, causing premature birth, stillbirth or infection in the newborn. Proper food handling and avoiding high risk foods can help prevent listeriosis.

Information for health professionals


Listeriosis is most often caused by eating foods contaminated with the bacteria Listeria monocytogenes. Listeria can be found in the environment including in soil and water. Between 2001 and 2010, an average of 12 cases of listeriosis per year has been reported to the BC Centre for Disease Control.


Symptoms can include:

  • fever
  • muscle aches
  • diarrhea.
  • Vomiting
  • headache

Listeriosis can also cause serious illness such as meningitis or blood infection, but these symptoms are relatively uncommon. Serious illness is more common in:

  • Pregnant women and newborns
  • Those with weakened immune systems
  • Older adults or seniors

Listeriosis can also cause miscarriage or stillbirth, premature delivery in pregnant women and illness in the newborn.

Symptoms usually start 1-14 days after exposure to Listeria in non-pregnant individuals. In pregnant women, it can take up to 4 weeks.


Listeria is found in the environment and animals can also carry the bacteria. Listeria can be found in a variety of foods, such as uncooked meats fruits and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheeses, deli meats, hotdogs and refrigerated seafood. Unpasteurized (raw) milk or foods made from unpasteurized milk may contain Listeria.


Even with prompt treatment, some infections result in death, especially in seniors and those with weakened immune systems.


Diagnosis is made by finding L. monocytogenes in various body fluids.


Listeriosis can be treated with antibiotics. If you have symptoms, consult a physician or health care professional.


People at risk should either avoid the following foods or consider the safer alternatives:

Foods to avoid

  • Soft cheeses even if they are pasteurized, such as Brie, Camembert, Feta, blue-veined and Mexican style cheese such as queso blanco or queso fresco
  • Unpasteurized dairy products (e.g. milk and cheese)
  • Deli meats
  • Hot dogs
  • Pates
  • Refrigerated seafood products such as smoked and candied salmon
  • Safer alternatives

    • Hard cheese (E.g., cheddar, Swiss, Colby) or cooked pasteurized soft cheese
    • Pasteurized milk and dairy products
    • Deli meats that are cooked until steaming hot (74º C/165º F or warmer)
    • Hot dogs that are cooked until steaming hot(74º C/165º F or warmer)
    • Canned pates or meat spreads
    • Canned or cooked fish and seafood products

    You can reduce the risk of listeriosis by following good food handling practices:

    • Cook raw foods of animal origin well (e.g. meat, seafood)
    • Wash raw vegetables before eating
    • Keep uncooked meats separate from vegetables and other ready-to-eat foods
    • Avoid unpasteurized milk and cheese and juice
    • Wash hands, knives and cutting boards after handling uncooked foods
    • Listeria may grow slowly even at refrigeration temperatures, so people at risk should not keep food in the refrigerator for more than 7 days

SOURCE: Listeria / Listeriosis ( )
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