Listeriosis (Listeria monocytogenes)
Listeriosis Fact Sheet
Minnesota Department of Health
Revised May, 2009
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Listeriosis Fact Sheet (PDF: 34KB/2 pages)
What is it?
Listeria monocytogenes is a bacterium that causes an illness called listeriosis. Listeriosis primarily affects people in high-risk categories: adults with weakened immune systems, pregnant women, and newborns.
What are the symptoms?
Common symptoms of listeriosis include fever, muscle aches, nausea, and diarrhea. If the infection spreads to the nervous system, other symptoms may develop, including headache, stiff neck, confusion, loss of balance, and convulsions.
Infected pregnant women may experience a mild, influenza-like illness; however, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or infection of the newborn.
Symptoms usually begin about 3 weeks after being exposed to Listeria. People who are not in the high-risk categories usually have no symptoms and suffer no ill effects from the infection.
How is it spread?
Listeria is found in soil and water. Animals can carry the bacterium without appearing ill and can contaminate foods of animal origin like meats and dairy products. Listeria has also been found in processed foods that are contaminated after processing, such as soft cheeses and cold cuts from the deli counter. Raw, unpasteurized milk or foods made from unpasteurized milk may also contain Listeria.
You can get listeriosis by eating foods contaminated with Listeria. Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy.
What should I do if I have symptoms?
Contact your health care provider. Listeriosis is generally diagnosed by culturing blood or spinal fluid for the bacterium. Antibiotics may be used to treat the infection.
How can I reduce the risk of developing listeriosis?
Recommendations for people who are at high risk, such as pregnant women and people with weakened immune systems:
- Do not eat hot dogs, deli meats, or luncheon meats unless they are reheated until steaming hot (at least 165ºF).
- Do not eat soft cheeses unless they have labels that clearly state they are made from pasteurized milk. Soft cheeses that may be made with raw, unpasteurized milk include:
- Blue-veined cheeses
- Mexican-style cheeses such as queso fresco, queso blanco, and Panela
- Do not drink unpasteurized milk and do not eat foods that contain unpasteurized milk.
- Do not eat refrigerated smoked seafood unless it is an ingredient in a cooked dish, such as a casserole. Canned or shelf-stable smoked seafood may be eaten. Examples of refrigerated smoked seafood include salmon, trout, whitefish, cod, tuna, or mackerel with the labels:
- Do not eat refrigerated pâtés and meat spreads. Canned or shelf-stable pâtés and meat spreads may be eaten.
General recommendations to prevent listeriosis
- Thoroughly cook meats including beef, pork, and poultry.
- Separate raw meats, poultry, and seafood from vegetables and cooked foods.
- Prevent cross-contamination in the kitchen by washing hands, cutting boards, countertops, knives, utensils, and other surfaces after handling raw foods.
- Wash raw fruits and vegetables before eating them.
- Refrigerate foods as soon as possible. Remember, “When in doubt, throw it out.”
- Use a refrigerator thermometer to make sure the temperature in your refrigerator stays at or below 40ºF.
- Clean your refrigerator regularly.
- Wash your hands with warm, soapy water for 20 seconds
- After using the bathroom
- After changing diapers
- After touching animals
- Before eating