What is listeriosis?

Listeriosis is a rare but potentially serious foodborne infection. It is caused by the bacteria Listeria monocytogenes. These bacteria are often found in the environment, particularly in soil, vegetation, and the feces of animals.

Listeriosis is most often caused by eating contaminated foods. A variety of foods can contain or become contaminated with Listeria, including unpasteurized dairy products, soft cheeses, deli meats, produce, and seafood products (e.g., smoked or candied salmon). Listeria can grow in foods that are wet, salty or sugary and can grow even when the food is refrigerated. Foods contaminated with Listeria often look, smell and taste normal. Listeriosis can also be transferred to a developing baby during pregnancy or to a newborn baby during delivery.

Who is at risk of infection?

Most people exposed to Listeria do not experience any symptoms. Some people may develop mild symptoms.

Pregnant women, newborns, older adults and those with weakened immune systems are at increased risk of getting a serious illness.

What are the symptoms?

Listeriosis can start with symptoms, such as:

• Fever
• Nausea
• Vomiting
• Diarrhea
• Muscle aches
• Headache

Listeriosis can cause serious illness such as meningitis, blood infection and even death. Symptoms of meningitis include fever, headache, stiff neck, loss of balance, decreased level of consciousness and seizures. Symptoms of a blood infection include fever, nausea, vomiting and severe muscle aches. Listeriosis can also cause miscarriage or stillbirths in pregnant women.

People who have symptoms of listeriosis should speak to their health care provider, especially if they are at increased risk of serious illness.

If you are at risk, how can you protect yourself?

If you are pregnant, an older adult, or have a weakened immune system you should either avoid or cook the following foods to steaming hot:

• Soft and mould-ripened cheese such as brie, camembert, feta, gorgonzola
• Unpasteurized (raw) dairy products (e.g., milk and cheese made from unpasteurized milk)
• Deli meats
• Patés
• Hot dogs
• Refrigerated seafood products

You can reduce the risk of listeriosis and other foodborne pathogens by following good food handling practices:

• Cook raw foods of animal origin well (e.g., meat, seafood, poultry and eggs) to at least 74°C (165 °F) and avoid raw products (e.g., raw smoked salmon)
• Keep the fridge at or below 4°C (40°F)
• Wash raw vegetables before eating
• Keep uncooked meats separate from vegetables and other prepared foods
• Avoid unpasteurized (raw) milk and juice as well as cheese made from unpasteurized milk
• Wash hands, knives and cutting boards after handling uncooked foods
• Bag raw meat, poultry, or fish separately from other food items
• Return home right away after shopping so that you can store all foods properly

Listeria may grow slowly even at refrigeration temperatures, so if you are at risk, you should not keep food in the refrigerator for more than 7 days. All leftover foods should be heated thoroughly to steaming hot (74°C) before eating.

For more information

For more information on food safety, see the following HealthLinkBC File:

• HealthLinkBC File #59a Food safety: Easy ways to make food safer

For more information about food safety during pregnancy, visit BC Centre for Disease Control Pregnancy and Food Safety: www.bccdc.ca/health-info/prevention-public-health/food-safety-pregnancy.