September 1999

What is listeriosis?

Listeriosis is caused by the bacterium Listeria monocytogenes. The disease affects primarily the fetus of pregnant women, newborns, and adults with weakened immune systems. Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill. It is not contagious from one person to another.

How do you get listeriosis?

You get listeriosis by eating or drinking contaminated food. Listeria monocytogenes is found in soil and water. Vegetables can become contaminated from the soil or from manure used as fertilizer. Animals can carry the bacterium without appearing ill and can contaminate foods of animal origin such as meat and dairy products. Unpasteurized (raw) milk or foods made from unpasteurized milk may also contain the bacterium. The bacterium has been found in a variety of raw foods, such as uncooked meats and vegetables, as well as processed foods, like hot dogs, that become contaminated after processing. If pregnant women eat contaminated food during pregnancy, their babies can be born with listeriosis.

What are the symptoms of listeriosis?

A person with listeriosis usually has a fever, muscle aches, and sometimes gastrointestinal symptoms, such as nausea or diarrhea. Headache, stiff neck, confusion, loss of balance, or convulsions may occur if the infection has spread to the nervous system. Once a person is exposed to the bacterium, it can take from three to 70 days for a person to actually become sick. The average is 31 days.

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Who is at risk for getting listeriosis?

Fetuses and the elderly are at greatest risk for listeriosis. People with weakened
immune systems are also at an increased risk. Healthy adults and children who eat contaminated foods may not become ill or they may get a mild gastroenteritis.

Are there tests for Listeria?

If you have symptoms such as those described above, and are concerned about a possible exposure, talk to your doctor. A blood or spinal fluid test will confirm the diagnosis.

Is there treatment for listeriosis?

For most Listeria infections, 10 to 14 days of antibiotic therapy is usually satisfactory. 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 may result in death.

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How can you reduce the risk for listeriosis?

In addition, people at high risk for complications from listeriosis, such as pregnant women and people with compromised immune systems, should

NOTE: Hard cheeses, processed cheeses, cream cheese, cottage cheese, or yogurt need not be avoided.

For more information

Division of Epidemiology and Disease Prevention
P.O. Box 70, Burlington, VT 05402
863-7240 or 1-800-640-4374 toll-free

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