Sign In
Boston Public Health Commission Home


What is Listeriosis?

Listeriosis is a serious infection caused by eating food contaminated with bacteria called Listeria monocytogenes. The disease is most serious in pregnant women, newborns, the elderly, and people with weakened immune systems.

How is it spread?

Listeria is found in nature in both water and soil. Listeriosis is spread by eating food contaminated with Listeria. It can be spread from person to person through sexual contact. It can also be spread from mother to child during pregnancy or childbirth.

Although healthy people may consume contaminated foods without becoming ill, those at increased risk for infection, such as people with compromised immune systems, can get listeriosis after eating food contaminated with even a few bacteria.

What are the symptoms?

Symptoms can include fever, muscle aches, and sometimes gastrointestinal symptoms such as nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur.

Infected pregnant women may not experience any symptoms or experience only a mild, flu-like illness; however, infections during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth.

How is it treated?

Several types of antibiotics are effective against Listeria. When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus or newborn. Even with prompt treatment with antibiotics, some infections result in death, particularly in the elderly and in persons with other serious medical problems.

Who is a greatest risk of getting seriously ill from Listeriosis?

In the United States, an estimated 2,500 persons become seriously ill with Listeriosis each year. Of these, 500 die. At increased risk are:

  • People with compromised immune systems such as:
    • People with AIDS
    • People with cancer, diabetes, or kidney disease
    • People with weakened immune systems due to other causes
  • People who take steroid medications
  • The elderly
  • Pregnant women are about 20 times more likely than other healthy adults to get Listeriosis. About one-third of Listeriosis cases occur during pregnancy and can lead to miscarriages and stillbirths.

Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.

How can I reduce my risk of getting Listeria?

General recommendations:

  • Thoroughly cook raw meat, 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 unpasteurized milk or foods made from unpasteurized milk.
  • Wash hands, knives, and cutting boards after handling uncooked foods.

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

  • Avoid soft cheeses such as feta, Brie, Camembert, blue-veined, and Mexican-style cheese. (Hard cheeses, processed cheeses, cream cheese, cottage cheese, or yogurt need not be avoided.)
  • Leftover foods or ready-to-eat foods, such as hot dogs, should be cooked until steaming hot before eating.
  • Although the risk of listeriosis associated with foods from deli counters is relatively low, pregnant women and immunosuppressed persons may choose to avoid these foods or thoroughly reheat cold cuts before eating.

What should I do if I’ve eaten food recalled because of contamination with Listeria?

The risk of an individual person developing Listeria infection after consumption of a contaminated product is very small. If you have eaten a contaminated product and do not have any symptoms, tests or treatment is not recommended, even if you are in a high-risk group. However, if you are in a high-risk group, have eaten the contaminated product, and within 2 months become ill with fever or signs of serious illness, you should contact your health care provider and inform them about this exposure.

Boston Public Health Commission
1010 Massachusetts Ave, 6th Floor, Boston, MA 02118.
Phone:(617) 534-5395 Email: