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updated 8/18/2006 2:28:33 PM ET 2006-08-18T18:28:33

Listeria monocytogenes, a common type of bacteria, has recently been recognized as an important public health problem in the United States. Eating food contaminated with the germ causes listeriosis, a serious infection affecting primarily pregnant women, newborns and adults with weak immune systems. It can be avoided by following a few simple recommendations.

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What are the symptoms of listeriosis?
A person with listeriosis suffers high fever, muscle aches and sometimes gastrointestinal symptoms such as nausea or diarrhea. If the infection spreads to the nervous system, it can cause symptoms such as headache, stiff neck, confusion, loss of balance or convulsions.

Infected pregnant women often experience only a mild, flu-like illness; however, infections during pregnancy can lead to miscarriage or stillbirth, premature delivery or infection of the newborn.

How common is this type of food poisoning?
In the United States, an estimated 2,500 persons become seriously ill with listeriosis each year. Of these, 500 die. At increased risk are:

  • Pregnant women are about 20 times more likely than other healthy adults to get listeriosis. About one-third of listeriosis cases happen during pregnancy.
  • Newborns themselves suffer the serious effects from their mother's infection during pregnancy.
  • Persons with weakened immune systems and diseases like AIDS, cancer, diabetes or kidney disease.
  • People who take steroid medications.
  • The elderly.

How do you "catch" listeriosis?
You get listeriosis by eating food contaminated with the germ. Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy. Although healthy people can consume contaminated foods without becoming ill, those at increased risk for infection may get listeriosis after eating food tainted with even a few bacteria. Those at risk can prevent Listeria infection by avoiding certain high-risk foods and by handling food properly.

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 can carry the bacterium without appearing ill and can contaminate foods of animal origin such as meats and dairy products. The germ 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 milk or foods made from unpasteurized milk may contain the bacterium.

Listeria is killed by pasteurization and cooking; however, in certain ready-to-eat foods such as hot dogs and deli meats, contamination may occur after cooking but before packaging.

The FDA has now approved a mixture of six bacteria-killing viruses that combat strains of Listeria — the blend can be sprayed on ready-to-eat meat and poultry products just before they are packaged.

How to protect yourself
The general guidelines recommended for the prevention of listeriosis are similar to those used to help prevent other food-borne illnesses, such as salmonella:

General recommendations for healthy people:

  • Thoroughly cook raw food from animal sources, such as beef, pork or poultry.

Additional recommendations for those at high risk, such as pregnant women and people with weak immune systems:

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. Even with prompt treatment, some infections result in death. This is particularly likely in the elderly and in persons with other serious medical problems.

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, tests or treatments aren't recommended. However, if you are in a high-risk group, have eaten the contaminated product, and within two months become ill with fever or signs of serious illness, you should contact your physician and inform him or her about this exposure.

Source: Centers for Disease Control and Prevention

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