Brie cheese

Fast Facts: Listeria 101

April 22, 2015

Listeria. This isn’t an everyday, household term – unless you are pregnant and avoiding foods that run a higher risk of contamination, or if you hear that your local grocer has announced a recall of foods with potential exposure to the bacteria. So when a doctor or health official does bring up the disease, it is important to know the basics.

We sat down with Chetan Jinadatha, M.D., M.P.H., assistant professor at the Texas A&M Health Science Center College of Medicine and an infectious disease expert, to find out the facts about this public health issue.

What is Listeria?

Listeria, also known as Listeria monocytogenes, is a hardy bacteria that lives in the intestinal tract of animals that produce milk, including goats, sheep, and cows. It can survive extreme heat and cold, and therefore is commonly found in foods such as processed meats and unpasteurized cheeses and milk. When consumed by human, the bacteria can cause a serious infection known as listeriosis.

Who is most at risk?

In the U.S., an estimated 1,600 people become seriously ill from listeria each year. The disease primarily affects elderly, pregnant women, newborns or very young children, and adults with weakened immune systems. However, rarely, persons without these risk factors can also be affected. Studies show that approximately 10 percent of humans may carry the bacteria, but only a small portion of those carriers develop listeriosis.

What are the symptoms of listeriosis?

Symptoms are similar to that of influenza, including fever, muscle aches, and gastrointestinal issues. Severe cases can lead to meningitis, for which symptoms may advance to include headache, stiff neck, light sensitivity, and confusion. In rare cases, listeriosis can lead to death.

Why is listeria the cause of a number of food recalls?

Listeria is most commonly found in unpasteurized dairy products, but can contaminate other foods, including processed meats, fruits and vegetables. Once introduced into a food processing plant, it is nearly impossible to isolate and clean the infected equipment, so the entire plant must be sterilized. Unlike other bacterial conditions, such as E. coli and Salmonella, refrigeration does not kill listeria. In fact, this particular bacteria can still multiply in temperatures as low as 32 degrees Fahrenheit. Even when the listeria bacteria freezes, it doesn’t die, but rather goes into dormancy; therefore, it survives at significantly lower temperatures than other bacteria.

How can consumers reduce their risks of contracting listeria?

Meat should be cooked to the USDA’s recommended temperatures, and all raw vegetables and fruit should be washed thoroughly. Refrigerators should be kept below 40 degrees Fahrenheit, and leftovers eaten within three to four days. Also stay abreast of any food recalls and discard products that are in question.

Ultimately, consumers can reduce their risk of contracting listeria by following standard, safe food preparation and storage.

— Debbie Field

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