There have been several outbreaks of foodborne illness and death from the bacteria E. coli in recent years. But other less well-known foodborne germs can cause illness, too. One that is especially dangerous for some people is a bacterium called Listeria monocytogenes. It can cause the illness listeriosis. In the U.S. about 2,500 people become seriously ill with listeriosis each year. Of these, about 500 die.
What are the symptoms of Listeria poisoning?
Listeriosis can cause fever, muscle aches and sometimes nausea or diarrhea. If it spreads to the nervous system it can cause headache, stiff neck, confusion, loss of balance and convulsions. If a pregnant woman is infected she may only feel slightly sick with flu-like symptoms. But the infection can cause miscarriage, stillbirth, premature labor or infection in the newborn.
Do you get sick right away after eating the contaminated food?
No. It generally takes about 3 weeks before you get sick.
Who is most at risk for listeriosis?
At increased risk are:
- Pregnant women, who are about 20 times more likely than other healthy adults to get listeriosis
- Newborns, who may be the most affected by their mother's infection during pregnancy
- People with weakened immune systems
- People with cancer, diabetes, or kidney disease
- People with AIDS, who are almost 300 times more likely to get listeriosis than people with normal immune systems.
- People who take steroid medications
- The elderly
Healthy adults and children sometimes get infected with Listeria, but they rarely become seriously ill.
How does Listeria get into food? The bacterium is in soil and water.
- Vegetables can get contaminated from the soil or from manure used as fertilizer.
- Animals can carry the bacterium without getting sick. They can contaminate meats and dairy products.
- Processed foods like soft cheeses and deli cold cuts can get contaminated after processing in the plant or anywhere along the way to your plate.
- Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacterium.
Listeria is killed by pasteurization and cooking.
What can I do to prevent listeriosis and other foodborne illness?
General recommendations:
- Thoroughly cook raw food from animal sources.
- Wash raw vegetables thoroughly before eating.
- Keep uncooked meats separate from vegetables, cooked foods and ready-to-eat foods.
- Avoid unpasteurized (raw) milk or foods made from unpasteurized milk.
- Wash hands, knives, and cutting boards after handling uncooked foods.
- Eat perishable and ready-to-eat foods as soon as possible.
People at high risk (like pregnant women and those with weakened immune systems) should also do the following:
- Don't eat hot dogs, lunch or deli meats unless they are reheated until steaming hot.
- Don't get fluid from hot dog packages on other foods, utensils, and food prep surfaces. Wash your hands after handling hot dogs, lunch and deli meats.
- Don't eat soft cheeses like feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses like queso blanco, queso fresco, and Panela unless the label says they're made from pasteurized milk.
- Don't eat refrigerated pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads are okay.
- Don't eat refrigerated smoked seafood, unless it's in a cooked dish like a casserole. These foods are usually labeled "nova-style," "lox," "kippered," "smoked," or "jerky." They're found in the refrigerator section, or sold at deli counters of grocery stores and delicatessens. Canned or shelf-stable smoked seafood is okay.
I'm pregnant. How would I know if I had listeriosis?
If you have symptoms like fever or stiff neck, consult your doctor. A blood or spinal fluid test can show if you have listeriosis.
What should I do if I've eaten a food recalled because of Listeria contamination?
Your risk of developing Listeria infection after eating a contaminated product is very small. If you don't have any symptoms you don't need any tests or treatment, even if you are in a high-risk group.
Contact your provider if you're in a high-risk group and get ill with fever or signs of serious illness within 2 months of eating the recalled food. Let them know that you were exposed.
Can listeriosis be treated?
When infection occurs during pregnancy, antibiotics can often prevent infection of the fetus or newborn. Babies with listeriosis get the same antibiotics as adults. Until the provider is sure of the diagnosis a combination of antibiotics is often used. Even with prompt treatment, some infections can cause death. This is most likely in the elderly and in people with other serious medical problems.
Most cases of listeriosis are preventable. Stay safe by using the prevention methods listed above.
Updated/Developed on 2/12/10 by Jennifer Johnson, BA English composition, Northwestern University. Reviewed by Steve Silverstein, MD. Published on 3/15/10.
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