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If you eat food contaminated with bacteria called Listeria, you could get so sick that you have to be hospitalized. And for certain vulnerable people, the illness could be fatal.
Contaminated food can bring Listeria into the home. Unlike most bacteria, Listeria germs can grow and spread in the refrigerator. So if you unknowingly refrigerate Listeria-contaminated food, the germs not only multiply at the cool temperature, they could contaminate your refrigerator and spread to other foods there, increasing the likelihood that you and your family will become sick.
Those most at risk for listeriosis—the illness caused by Listeria monocytogenes—include pregnant women, older adults and people with compromised immune systems and certain chronic medical conditions (such as HIV/AIDS, cancer, diabetes, kidney disease, and transplant patients). In pregnant women, listeriosis can cause miscarriage, stillbirth, and serious illness or death in newborn babies.
What foods could be contaminated?
Listeria has been linked to a variety of ready-to-eat foods, including deli meats, hot dogs, smoked seafood and store-prepared deli-salads. A draft study released May 10, 2013 by the Food and Drug Administration (FDA) and the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) evaluates the risk of listeriosis associated with foods prepared in retail delis. There are many steps that deli operators and processing establishments that supply food to delis can follow to reduce the risk of listeriosis.
FDA and FSIS recommend that consumers at risk for developing listeriosis—including older adults, pregnant women and people with compromised immune systems—reheat hot dogs and lunch meats until steaming hot.
At-risk consumers are also advised to avoid unpasteurized milk and soft cheeses (such as feta, brie, camembert, blue-veined cheeses, "queso blanco," "queso fresco" or Panela), unless they are made with pasteurized milk.
And Listeria can sometimes be found in other foods. In 2011, a multi-state outbreak of listeriosis tied to contaminated cantaloupes caused illnesses and deaths.
Donald Zink, Ph.D, senior science advisor at FDA's Center for Food Safety and Applied Nutrition, says FDA is aware of cases of foodborne illness caused by bacteria that can live in the kitchen and spread to foods that had not been contaminated.
Consumers are advised to wash all fruits and vegetables under running water just before eating, cutting or cooking, even if you plan to peel the produce first. Scrub firm produce such as melons and cucumbers with a clean produce brush.
To further protect yourself and your family from Listeria, follow these steps:
Chilling food properly is an important way of reducing risk of Listeria infection. Although Listeria can grow at refrigeration temperatures, it grows more slowly at refrigerator temperatures of 40 degrees F or less.
- Keep your refrigerator at 40 degrees F or lower and the freezer at 0 degrees F or lower.
- Wrap or cover foods with a sheet of plastic wrap or foil or put foods in plastic bags or clean covered containers before you place them in the refrigerator. Make certain foods do not leak juices onto other foods.
- Place an appliance thermometer, such as a refrigerator thermometer, in the refrigerator, and check the temperature periodically. Adjust the refrigerator temperature control, if necessary, to keep foods as cold as possible without causing them to freeze. Place a second thermometer in the freezer to check the temperature there.
- Use precooked and ready-to-eat foods as soon as you can. The longer they are stored in the refrigerator, the more chance Listeria has to grow.
"If you have leftovers in your refrigerator, it’s best to throw them out after three days, just to be sure,” says Zink. “It's better to be safe than sorry."
Listeria can contaminate other food through spills in the refrigerator.
- Clean up all spills in your refrigerator right away—especially juices from hot dog and lunch meat packages, raw meat, and raw poultry. Consider using paper towels to avoid transferring germs from a cloth towel.
- Clean the inside walls and shelves of your refrigerator with warm water and liquid soap, then rinse. As an added measure of caution, you can sanitize your refrigerator monthly using the same procedures described below for kitchen surfaces.
Listeria can spread from one surface to another.
- Thoroughly wash food preparation surfaces with warm, soapy water. As an added precaution you should sanitize clean surfaces by using any of the kitchen surface sanitizer products available from grocery stores, being careful to follow label directions.
You can make your own sanitizer by combining 1 teaspoon of unscented bleach to one 1 quart of water, flooding the surface and letting it stand for 10 minutes. Then rinse with clean water. Let surfaces air dry or pat them dry with fresh paper towels. Bleach solutions get less effective with time, so discard unused portions daily.
- A cutting board should be washed with warm, soapy water after each use. Nonporous acrylic, plastic, or glass boards can be washed in a dishwasher.
- Dish cloths, towels and cloth grocery bags should be washed often in the hot cycle of your washing machine.
- It’s also important, to wash hands with warm water and soap for at least 20 seconds before and after handling food.
This article appears on FDA's Consumer Updates page, which features the latest on all FDA-regulated products.
Updated: May 10, 2013
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