What is listeriosis?
Listeriosis is a serious illness caused by a bacterium called Listeria monocytogenes.

Where are the bacteria found?
The bacteria are found in soil and water. Animals can carry the bacteria without appearing ill.

How do these bacteria spread?
Humans may become infected by eating contaminated foods. Vegetables can become contaminated from the soil or from manure used as fertilizer. Animals can contaminate foods of animal origin such as meats and dairy products. The bacteria have been found in raw foods, such as uncooked meats and vegetables, and in foods that become contaminated after processing, such as soft cheese and cold cuts at the deli counter. Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacteria. Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy.

Who gets listeriosis?
The disease affects primarily pregnant women, newborns, the elderly, persons with weakened immune systems, cancer, diabetes, kidney disease, AIDS, and persons who take corticosteroid medications. Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.

What are the symptoms of listeriosis?
Persons infected with Listeria may have fever, muscle aches, and sometimes nausea and diarrhea. Symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can also occur. Infected pregnant women may experience only a mild illness; however, infection during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth.

How soon do symptoms appear?
The symptoms can appear from 3 - 70 days after exposure. In most cases, symptoms develop 3 weeks after exposure.

What is the treatment for listeriosis?
When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus or newborn. Babies with listeriosis receive the same antibiotics as adults, although a combination of antibiotics is often used until physicians are certain of the diagnosis. Even with prompt treatment, some infections result in death. This is particularly likely in the elderly and in persons with other serious medical problems.

How can listeriosis be prevented?                             

  • General recommendations include the following:
  • Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.
  • Wash raw vegetables thoroughly before eating.
  • Keep uncooked meats separate from vegetables, cooked foods, and ready-to-eat foods.
  • Avoid raw (unpasteurized) milk or foods made from raw milk.
  • Wash hands, knives, and cutting boards after handling uncooked foods.

Recommendations for persons at high risk, such as pregnant women and persons with weakened immune systems, in addition to the recommendations listed above:

  • Do not eat soft cheeses such as feta, Brie, Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pasteurized milk.
  • Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot.

This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.


For additional information on this disease, visit the Centers for Disease Control and Prevention website.

To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.