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Sanitation and Illness

Listeria: Answers to Common Questions

Suzanne Driessen

Listeriosis is a foodborne illness caused by bacteria (Listeria monocytogenes) that grow at refrigeration temperatures. Listeria monocytogenes is found in the intestines of animals and in soil, water and plants.

Q. What is listeria?

A. Listeria monocytogenes is bacteria found in soil and water. Animals carry it without appearing ill, which in turn contaminates food of animal origin, such as meat and dairy products. Vegetables grown in soil fertilized with tainted manure can become contaminated.

Q: What foods are most often contaminated with listeria?

A. Raw milk, soft cheese like feta, brie, or raw vegetables can contain listeria monocytogenes. Poultry, meats (including hot dogs and lunch meat), and prepared, chilled ready-to-eat foods are also at higher risk.

Q. How is listeria killed?

A. Pasteurization and heat used to prepare ready-to-eat processed meats kill listeria. However, contamination can occur after processing. Listeria grows at refrigeration temperatures and multiplies each day the contaminated product is stored.

Q. What are the symptoms?

A. Symptoms, including nausea, vomiting, diarrhea, headache, chills and fever in otherwise healthy adults generally begin 2 days to 3 weeks after eating contaminated food. In pregnant women, listeria typically causes flu-like illness with fever and chills. In other people, symptoms may include fever, severe headache and stiff neck.

Q: How do I reduce my risk for listeriosis?

A. Reduce your risk for listeriosis by:

Q: For people at a high risk (young children, elderly and people with low immunity) are there extra precautions to take?

A. Yes. People at high risk should follow these guidelines:

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Revised by Suzanne Driessen 2016

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