Listeria: Are You at Risk?

Sept. 29, 2011 -- Are you at risk from listeria, the deadly bacteria now in the news?

The death toll is rising in the ongoing outbreak from contaminated cantaloupe. It's now the largest outbreak of food-borne illness in more than a decade.

Suddenly the spotlight is on listeria. What is it? Where is it found? Who's at risk? What can we do about it? What are the symptoms of listeriosis, and how is it treated? Here's WebMD's FAQ.

What Is Listeria?

Listeria monocytogenes leads a double life. It's commonly found in the environment, where it feeds on decaying plant matter. It's found in soil, animal feed, groundwater, and sewage. It can also be carried in the guts of cattle and poultry.

But when listeria gets into humans, it changes form. It becomes a bacterial parasite that lives inside -- and feeds on -- human cells. The disease caused by listeria is called listeriosis.

People with lowered immunity -- the elderly, cancer patients, people taking immunity-suppressing drugs, and pregnant women -- are particularly vulnerable to listeriosis.

How Do People Get Listeriosis?

By far the most common way people get listeriosis is by eating foods contaminated with listeria.

However, newborns can be directly infected during birth. For every 100,000 U.S. births, there are 8.6 neonatal infections. Listeriosis is one of the most common causes of neonatal meningitis.

What Should I Do If I Bought a Suspect Cantaloupe?

All of the cantaloupes in the current listeria outbreak came from Jensen Farms, a Colorado-based company. Although some of these cantaloupes carry a distinctive sticker, not all contaminated fruit will be marked. Ask your grocer if the cantaloupe you bought is from Jensen Farms.

If you suspect that you have a contaminated cantaloupe, do not try to wash off the listeria. Griffin of the CDC notes that it's not clear whether a listeria-contaminated melon carries listeria on the inside as well as on the outside.

So dispose of suspect cantaloupe in a sealed bag, and make sure it will not be eaten by animals or other people.

But that's not all you should do.

One study found that once a listeria-contaminated food product was in a person's home, 11% of all food samples in their refrigerators also were contaminated. Nearly two-thirds of people with listeria infections turn out to have listeria growing in their refrigerators.

So clean your refrigerator if you think you may have purchased a contaminated cantaloupe. Wash the fridge thoroughly with soap and water. Then wipe it down with a diluted solution of chlorine bleach.

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.