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Department for Public Health
Epidemiology and Health Planning
(502) 564-2339

  What is Listeriosis?

Listeriosis is a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes.  It has been recognized as an important public health problem in the United States, with an estimated 2,500 persons becoming seriously ill each year, of which, 500 die.  The disease affects primarily pregnant women, newborns, and people with weakened immune systems.  It can be avoided by following a few simple food avoidance and food preparation guidelines.

What are the symptoms of listeriosis?

Symptoms of listeriosis 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 experience only a mild, flu-like illness; however, infections during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth.


What is my risk for listeriosis?

In the United States, it is reported that 500 people a year die from listeriosis.  Some people have higher risk than others.  At increased risk are:

Pregnant women – They are about 20 times more likely than other healthy adults to get listeriosis.  About one-third of listeriosis cases happen during pregnancy.
Newborns – Newborns rather than the pregnant women themselves suffer the serious effects of infection in pregnancy.
Persons with weakened immune systems
Persons with cancer, diabetes, or kidney disease
Person with AIDS – They are almost 300 times more likely to get listeriosis than people with normal immune systems.
Persons who take glucocorticosteroid medications
The elderly
Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.

How does Listeria get into food?

Listeria monocytogenes is found in soil and water.  Vegetables can become contaminated from the soil or from manure used as fertilizer.  Animals carry the bacterium without appearing ill and can contaminate foods of animal origin such as meats and dairy products.  The bacterium has been found in a variety of raw foods, such as uncooked meats and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheeses and cold cuts at the deli counter.  Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacterium.

How do you get Listeriosis?

You can get listeriosis by eating food contaminated with Listeria.  Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy.  Although healthy persons may consume contaminated foods without becoming ill, those at increased risk for infection can probably get listeriosis after eating food contaminated with even a few bacteria.  Persons at risk can prevent Listeria infection by avoiding certain high-risk foods and by handling food properly.

How can you reduce your risk for listeriosis?

General recommendations:

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 and from 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 above recommendations:

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 food from deli counters is relatively low, pregnant women and immunosupressed persons may choose to avoid these foods or thoroughly reheat cold cuts before eating.
What should you do if you’ve eaten a food recalled because of Listeria contamination?

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, we do not recommend that you have any tests or treatment, 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 physician and inform him or her about this exposure.

Can listeriosis be treated?

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. 


Last Updated 7/31/2007