How does Listeria get into food and who needs to worry about it?

Q.Occasionally I read about an outbreak of Listeria from some food source. Where does Listeria come from and who carries it? Is it naturally occurring? Is infection with Listeria common?

A.Listeria is a type of bacteria found in soil and water. It can contaminate fruits and vegetables from these sources. Animals, in turn, eat the contaminated plants and pass the bacteria along in their meat or milk.

The high temperatures of cooking or pasteurization should kill these bacteria. Yet sometimes, food can become contaminated after cooking but before packaging. This can happen with foods such as hot dogs or deli meats.

Getting sick from Listeria is extremely unusual. Certain groups of people are at high risk to become sick from Listeria. Anyone with a weakened immune system is at risk. Pregnant women, infants, and the elderly are also at greater risk of listeria infection and its complications.

Listeriosis can cause fever, muscle pain, and sometimes nausea or diarrhea. It can spread to the brain and nervous system. This can cause meningitis or seizures. In pregnant women, Listeria crosses the placenta and can cause miscarriage.

If you've worried about something you ate or drank, you don't need tests or treatment unless you become ill or are in a high-risk group. Listeriosis can be detected with a blood test and treated with antibiotics.

Listeria is a very uncommon disease, fortunately. But following these precautions can lessen your risk:

• Thoroughly cook meat.
• Wash raw vegetables before eating them.
• Keep uncooked meat separate from cooked and prepared foods.
• Don't eat or drink unpasteurized dairy products.
• Wash your hands, utensils, and cutting boards after they have touched uncooked foods.

If you are in a high-risk group for Listeria infection, then you should take these additional precautions:

• Avoid deli meats, luncheon meat, or hot dogs unless they are cooked to steaming hot.
• Do not eat soft cheeses such as Brie, Camembert, blue-veined cheeses, and others unless the label clearly says they were made from pasteurized milk.
• Do not eat pâtes or meat spreads. Canned meat spreads or pâtes are okay.
• Do not eat refrigerated, smoked seafood unless it is cooked.

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