What You Should Know About Listeria

Listeria monocytogenes. Science Picture Company/Getty Images

With the many food recalls we see in today's society, most of us are familiar with the common culprits E. coli and salmonella. However, contamination with the bacterium listeria monocytogenes is also possible, so you need to know about it as well.

Listeria infections (listeriosis) occur when a person eats a food contaminated with the listeria monocytogenes bacteria. It is most often found in processed meats such as hot dogs and deli meats (both prepackaged and at the deli counter), soft cheeses and smoked seafood.

Raw or unpasteurized milk and products made with it commonly contain listeria. Most healthy people who eat these foods will not get listeriosis even if the product is contaminated.

Who Is at Risk?

Most healthy people who eat food contaminated with listeria monocytogenes will not get sick. Some may have mild symptoms but a majority of us will never know it. However, there are certain groups of people who can be very seriously affected by this bacteria.

Those at high-risk include:

  • Pregnant women
    Pregnant women are about 13 times more likely to get listeriosis than the general public. About one in six confirmed cases of listeriosis is a pregnant woman. Listeriosis can cause severe complications during pregnancy.
  • Newborns
    Newborn babies contract listeriosis when their mothers eat contaminated food. Infections can cause life-threatening complications.
  • Those with Weakened Immune Systems
    People who have compromised immune systems, cancer, diabetes, alcoholism, liver or kidney disease or AIDS are at high risk for complications from listeria infections. People with AIDS are 300 times more likely to be affected by listeria infections than the general population.
  • Older Adults

Symptoms of Listeriosis

Symptoms of listeriosis generally start with gastrointestinal symptoms such as diarrhea and stomach cramps. However, once it is diagnosed, these symptoms have usually been followed by:

  • Fever
  • Muscle Aches
  • Headache
  • Stiff neck
  • Confusion
  • Loss of balance
  • Convulsions (seizure)

Pregnant women are among the highest at-risk groups for listeriosis and symptoms during pregnancy are different than they are for others.

Pregnant women who develop listeriosis may experience flu-like symptoms but the infection can lead to:

  • Miscarriage
  • Stillbirth
  • Premature delivery
  • Life-threatening infections in the newborn

Treatment Options

Listeria infections are treated with antibiotics. Anyone who is at high risk for listeriosis that experiences flu-like symptoms within two months of eating contaminated food (during known outbreaks) should seek medical attention.

Listeriosis can result in death, even when treated. Almost all listeria-related deaths occur in those at high risk.

Can It Be Prevented?

The best way to prevent a listeria infection is to use proper food safety precautions.

Wash Your Hands

Washing your hands thoroughly while you are preparing food and before you eat is essential to preventing any type of foodborne illness.

Make Sure Your Food Is Thoroughly Washed and Fully Cooked

Undercooked meats and dirty vegetables are the primary culprits in spreading listeria. Making sure you thoroughly wash all of your fruits and vegetables (especially those that will not be cooked) and cooking all meats to the proper temperatures is essential.

Even if produce will be peeled, it should be washed first. Keep raw and cooked foods separated and do not place cooked foods on cutting boards or dishes that have held raw meat.

Meats should be cooked until their internal temperatures reach:

  • Poultry: 165 degrees F
  • Beef: 145 degrees F
  • Pork: 145 degrees F

Ground meats should be cooked until it is brown all the way through and the internal temperature is at least 160 degrees F (beef, pork, veal, and lamb) or 165 degrees F (turkey and chicken).

Store Leftovers at Proper Temperatures

Storing food at proper temperatures is important in preventing the growth of listeria monocytogenes. Refrigerators should be kept below 40 degrees F and freezers below 0 degrees F. However, listeria can grow on some foods even in the refrigerator.

Special Precautions for Those at High Risk

Because listeriosis can be so serious for high-risk groups such as pregnant women, it is best to avoid certain foods completely.

The CDC recommends that those in high-risk groups not eat hot dogs, deli meats, cold cuts or sausages unless they are heated to at least 160 degrees F right before serving. Do not eat soft cheeses such as feta, brie or queso blanco unless the label specifies that it was made with pasteurized milk. Do not eat refrigerated smoked seafood such as lox or smoked salmon unless it is included in a cooked dish or it is served in a shelf-stable package rather than the refrigerated or deli section. Do not eat refrigerated meat spreads or paté (sold in the refrigerated or deli section) that are not shelf stable.


"Definition" Listeriosis (Listeria infection) 07 Oct 11. US Centers for Disease Control and Prevention. 17 Feb 12.

"People at Risk" Listeriosis (Listeria infection) 31 Jan 12. US Centers for Disease Control and Prevention. 17 Feb 12.

"Safe Minimum Cooking Temperatures" Keep Food Safe. FoodSafety.gov. US Department of Health and Human Services. 17 Feb 12.

"Prevention" Listeriosis (Listeria infection) 17 Oct 11. The US Centers for Disease Control and Prevention. 17 Feb 12.

"Treatment & Outcomes" Listeriosis (Listeria infection) 27 Sep 11. The US Centers for Disease Control and Prevention. 17 Feb 12.

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