What Is Listeria?

It can happen to anybody -- you eat something and it doesn’t agree with you. You feel sick to your stomach, and you might come down with diarrhea. After a couple of days (or less in most cases), the trouble goes away and that’s the end of it.

A possible source of the illness: listeria, one of the causes of food poisoning.

It’s triggered by listeria bacteria that can live in soil, water, dust, animal poop, and other substances. You can get sick if you eat food that carries it.

For most healthy people, the infection doesn’t pose much of a threat, even if it makes you sick for a day or two.

But for some people, the infection can be serious or even life-threatening, particularly pregnant women and their babies, people whose immune systems aren’t working right, and seniors. If you belong to any of those groups, you need to be extra cautious.

What Causes Listeria?

Listeria is caused by bacteria that can grow at cold temperatures, like those inside a refrigerator. Even freezing doesn’t stop it. When it contaminates food, you can’t see, smell, or taste it.

People pick up the infection most often from deli meats that aren’t processed properly or from dairy products made from milk that isn’t pasteurized -- in other words, the milk hasn’t been heated to kill germs.

Other common sources of outbreaks are:

  • Cantaloupes
  • Hot dogs
  • Soft cheeses



When you get a listeria infection, the signs typically include:

They could appear a few days after you eat the bad food, or they might take a couple of months to show up. If you have any of those symptoms, contact your doctor.

If the infection spreads to your nervous system, it’s more serious. This happens most often with the very young, the very old, and people with weakened immune systems. The signs could be:

Go for emergency care or call 911 if you or a loved one have any of these symptoms.

When you’re pregnant, you need to take special care because you have an increased risk of listeria in the blood. Call your doctor if you have:

A mild case of listeria may need no treatment at all. For a more serious case, the doctor may use antibiotics.

Foods to Watch Out For

There’s no vaccine to protect against listeria. So it’s important to be on guard. The main foods that can make you sick include:

  • Raw vegetables contaminated by soil or by manure that was used as fertilizer
  • Animal meat that is contaminated with listeria
  • Milk that wasn’t pasteurized, and other products made from it
  • Processed foods such as deli meats and hot dogs that are contaminated after they’re produced

How to Protect Yourself

Be sure to wash your hands. Clean them well with warm, soapy water before you start cooking. If you handle raw meat or poultry, wash them afterward.

Here are some other good ideas for cleaning, handling, and cooking food:

  • Clean all kitchen surfaces, cutting boards, and utensils with hot, soapy water when you finish cooking.
  • Scrub raw vegetables with a brush under running water.
  • Cook meat, poultry, and egg dishes until they reach 160 F in the center. Use a meat thermometer to make sure. Keep uncooked meat and poultry away from other food.
  • Use hot dogs within a week after you open the package, and deli and luncheon meats within 3 to 5 days after opening.
  • Wash your hands with soap before handling a whole melon. Clean it with a brush under running water. Eat slices promptly. Throw out anything that sits at room temperature more than 4 hours.
  • Keep the temperature below 40 F in the refrigerator, and below 0 F in the freezer.


People Who Should Be Extra Careful

Pregnant women, and especially pregnant Hispanic women, are more likely than most people to come down with listeria. An infection, even one that affects the mother mildly, can have very serious effects on the baby, including premature birth or even stillbirth.

If a baby is born with listeria, symptoms might include:

  • Little interest in feeding
  • Fussiness
  • Fever
  • Vomiting

Pregnant women and people in the other at-risk groups -- seniors and people whose immune systems are weak -- need to be especially careful. They should not eat:

  • Hot dogs, cold cuts, or deli meats unless they have been heated to 165 F
  • Refrigerated meat spreads or refrigerated smoked seafood. Foods that do not need refrigeration, such as canned tuna, are OK.
  • Soft cheeses that are made from milk that has not been pasteurized. Some examples: brie, camembert, feta, queso panela, queso blanco and queso fresco. But if the label says specifically that the cheese is made from pasteurized milk, it’s OK.

Recalled Foods

Just as cars might be recalled by their makers because of safety defects, companies that make and sell food sometimes have to recall it.

News media report these recalls when they happen, and the federal foodsafety.gov website lists recalls on its home page.

If you see a recall for food that you’ve eaten, watch for symptoms of listeria, and contact your doctor if you have any.

WebMD Medical Reference Reviewed by Sabrina Felson, MD on December 21, 2016



CDC: “Listeria (Listeriosis).”

UpToDate: “Clinical manifestations and diagnosis of Listeria monocytogenes infection.”

Foodsafety.gov: “Recall & Alerts.”

KidsHealth: “About Listeria.”

Mayo Clinic: “Listeria infection.”

Ohioline (Ohio State University Extension): “Listeria monocytogenes: A concern for pregnant women and older adults.”

© 2016 WebMD, LLC. All rights reserved.