What is listeria and how do we prevent it?

Listeriosis, a serious infection caused by eating food contaminated with the bacterium Listeria monocytogenes, has recently been recognized as an important public health problem in the United States. In the United States, an estimated 2,500 persons become seriously ill with listeriosis each year. Of these, 500 die.

The disease affects primarily persons of advanced age, pregnant women, newborns, and adults with weakened immune systems, however healthy children and adults can get infected as well. About one-third of listeriosis cases happen during pregnancy.

Listeria monocytogenes has been recognized as a human pathogen for 60 years, but food was not thought to be a vehicle of transmission until recently. 

Vegetables can become contaminated from the soil or from manure used as fertilizer. Animals can carry the bacteria without appearing ill and can contaminate foods of animal origin such as meats and dairy products. The bacteria can be 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 (raw) milk or foods made from unpasteurized milk may contain the bacteria.

Symptoms vary and depend on the individual’s susceptibility, but may include fever, fatigue, nausea, vomiting and diarrhea.

Listeria has the unusual ability to grow in cold environments, including certain refrigerated or frozen foods.

How can you reduce your risk for listeriosis?

General recommendations:

• Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.
• Wash raw vegetables thoroughly before eating.
• Keep uncooked meats separate from vegetables and from 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.
• Consume perishable and ready-to-eat foods as soon as possible

Recommendations for persons at high risk, such as pregnant women and persons with weakened immune systems, in addition to the recommendations listed above:

• Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot.
• Avoid getting fluid from hot dog packages on other foods, utensils, and food preparation surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats.
• Do not eat soft cheeses such as feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pastuerized milk.
• Do not eat refrigerated pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads may be eaten.
• Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna or mackerel, is most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” The fish is found in the refrigerator section or sold at deli counters of grocery stores and delicatessens. Canned or shelf-stable smoked seafood may be eaten.

Source: http://www.cdc.gov/nczved/dfbmd/disease_listing/listeriosis_gi.html#what