September 18, 2002
Contact: CDC, Media Relations
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Press Release

Update: Listeriosis Outbreak Investigation

CDC is working with several State Health Departments in investigating a cluster of Listeria infections. The Listeria bacteria has been isolated and pulsed-field gel electrophoresis (PFGE)-matched in 26 patients, which suggests that these patients acquired illness from the same food.
Case-patients live in southeastern Pennsylvania (12), New York City (8), New York State (2), Maryland (2), Connecticut (1), and Michigan (1). All patients were hospitalized and four have died (2 in New York City, 1 in Michigan and 1 in Pennsylvania). Federal and state public health officials are working to determine the food that caused these illnesses. These illnesses were first reported in the summer, and cases continued to be reported in September.

In addition to the 26 patients whose illnesses have been confirmed as part of the cluster, CDC and State Health Departments are investigating other cases of Listeria infection in the same region. Strains from some patients have already been shown to be different from the outbreak strain; these illnesses are part of the "background" of sporadic Listeria infections that are expected to occur. However, testing of Listeria isolates from about 50 more persons is ongoing; some of these will likely be the outbreak strain and some will not.

LISTERIA BACKGROUND
Listeriosis is a very serious illness. It affects primarily pregnant women, newborns, adults with weakened immune systems, and the elderly. The initial symptoms are often fever, muscle aches, and sometimes gastrointestinal symptoms such as nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur. Pregnant women may experience only a mild, flu-like illness; however, infections during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth.

To reduce the risk of listeriosis:

• 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 raw (unpasteurized) milk or foods made from raw milk.
• Wash hands, knives, and cutting boards after handling uncooked foods.

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

• Pregnant women and immunosupressed persons may choose to avoid foods from deli counters or thoroughly reheat cold cuts before eating.
• Heat left-over foods and ready-to-eat foods, such as hot dogs, until steaming hot just before eating.
• Avoid soft cheeses such as feta, Brie, Camembert, blue-veined, and Mexican-style cheese. (Hard cheeses, processed cheeses, cream cheese, cottage cheese, and yogurt need not be avoided.)

For more information about Listeria, contact your local or state health department or healthcare provider, or visit the CDC web site at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/listeriosis_g.htm.

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