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Food Poisoning Health Center

Listeria: Are You at Risk?

FAQ on Deadly, Little-Understood Listeria Bug Behind Cantaloupe Outbreak
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What About Other Produce or Foods?

If there is a recall or any suspicion that there is listeria in your food -- be it lettuce, cheese, or hot dogs -- throw it out. Do not try to wash the food because there is no way to ensure that the listeria is just on the surface. Listeria cannot be seen and it does not change the way the food looks, so always play it safe. Officials also ask that you wrap the food in a plastic bag before throwing it out to prevent another person or an animal from eating it.

As for all other produce, the FDA advises 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.

What Makes Listeria Dangerous?

"Listeria is a very uncommon cause of illness," Patricia Griffin, MD, chief of the CDC's enteric disease epidemiology branch, tells WebMD.

That said, mild gastrointestinal illness from listeria probably is quite common. Listeriosis -- when listeria escapes the gut and invades the bloodstream -- is rare. The CDC now estimates there are only about 800 listeriosis cases a year in the U.S.

Whether listeria causes illness, Griffin says, depends on a combination of three things: a person's susceptibility, how much listeria a person has been infected with, and the virulence of the particular listeria strain.

Another thing that makes listeria dangerous is that it can survive for a long time, even at refrigerator temperatures.

"Listeria can live in microfilms," Griffin says. Microfilms are sticky mats of bacteria that don't easily wash away.

Microfilms may be one reason why listeria can survive and thrive for years in food processing plants.

But what makes listeria most dangerous is that once it has entered the bloodstream, it gets into the lymph system and into the brain. Encephalitis and meningitis are major causes of death and disability in people with listeriosis.

Why Are Pregnant Women Susceptible to Listeria?

As pregnancy progresses, a woman's cell-mediated immune responses are suppressed. This makes her body more vulnerable to invasion by listeria, particularly during the third trimester.

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