“Listeriosis is a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes,” explains Jennifer Hunter, MPH, DrPH, an epidemiologist with the Centers for Disease Control and Prevention (CDC).
Listeria Makes You Sick When You Eat Foods Contaminated With the Bacteria
The type of listeria that poses a grave threat to humans is Listeria monocytogenes. It tends to make its way into our systems when we eat contaminated foods. “Listeria monocytogenes can grow at refrigeration temperatures [whereas] most pathogens cannot,” says Linda Harris, PhD, a department chair and specialist in food microbiology at the University of California in Davis.
While many foods may be contaminated with nonthreatening amounts of Listeria monocytogenes, the bacteria’s ability to withstand cold conditions can allow small communities to reproduce and form colonies large enough to cause illness or a serious infection, explains Robert Buchanan, PhD, the director of the University of Maryland’s Center for Food Safety and Security Systems in Baltimore.
Many foods that are left sitting out for a few hours at room temperatures — especially meats, cut fruit, and dairy foods — are risky. “At room temperature, listeria will double every 20 minutes,” Buchanan says. “In a refrigerator at 40 degrees, they double about once a day.”
Taking that into account, it’s important to eat foods soon after pulling them out of the fridge, and to refrigerate them as soon as possible if you’re not going to eat them, he says.
Learn More About How and Why Listeria Makes You Sick
Causes and Risk Factors for Listeria Infection
- Queso fresco and other soft cheeses (Brie, Camembert, feta, queso blanco, queso panela, blue cheese)
- Raw or lightly cooked sprouts (alfalfa, clover, radish, mung bean)
- Hot dogs and deli meats
- Smoked fish (unless canned or shelf-stable, or part of a cooked dish like casserole)
- Unpasteurized (raw) milk and dairy products (soft cheese, ice cream, and yogurt)
How Is Listeria Infection Diagnosed?
Treatment and Medication Options for Listeria Infection
If symptoms do not go away in that amount of time, it’s a good idea to check with your doctor to make sure the infection is not spreading or to determine what else could be causing the problems.
Learn More About Treatment for Listeria Infections
Listeria Infections Can Be Much More Dangerous if You’re Pregnant
RELATED: How to Tell the Flu From a Common Cold or Something Else
Learn More About Specific Listeria Risks in Pregnant Women
Prevention of Listeria Infection
- Always cook or heat meat products before eating them.
- Promptly refrigerate any foods you’re not going to eat right away.
- If you handle or prepare raw meat, be sure to wash your hands and any food prep equipment before you work with other foods.
It’s important to pay attention to news of listeria outbreaks in your area. The U.S. Department of Health and Human Services offers info about all food-related recalls and health issues at FoodSafety.gov, and you can sign up for automatic alerts about listeria concerns in your region.
How DNA Sequencing Has Changed the Way Listeria Outbreaks Are Tracked
Learn More About How to Prevent Listeria Infection
People over 65 and those who are immunocompromised face a greater risk of severe complications from listeriosis, including:
- Sepsis (infection of the blood)
- Meningitis (inflammation of the membranes surrounding the brain and spinal cord)
- Encephalitis (inflammation of the brain)
Related Conditions of Listeria Infection
Resources We Love
Centers for Disease Control and Prevention
As one of the leading health organizations in the United States, the CDC tracks listeriosis outbreaks, offers answers to the most common questions, and outlines a list of the riskiest foods. You can also keep tabs on CDC projects like whole genome sequencing, which aims to prevent foodborne-illness outbreaks like listeriosis.
KidsHealth From Nemours
KidsHealth.org offers doctor-reviewed advice on hundreds of topics, free lesson plans and programs for educators, and tools like videos and slideshows to help families stay healthy. Check out their informational page on listeria infections, which outlines steps to take if you suspect your child has eaten contaminated food.
Whatever you want to know about listeria infections, the Mayo Clinic has you covered. This site provides info on risk factors, symptoms, diagnosis, and treatment options, as well as tips to help you prepare for an appointment with your doctor.
U.S. Food and Drug Administration
Want to know how to keep listeria out of your food? The FDA outlines which foods are no-no’s and offers key food safety tips to reduce the risk of contamination. You’ll also find advice for maintaining your kitchen and refrigerator as clean, sanitary spaces.
U.S. National Library of Medicine
Have a question about listeria and listeriosis? The U.S. National Library of Medicine will direct you to a number of high-quality government and nongovernment health agencies — like the FDA, CDC, and Mayo Clinic — to help you fill in the blanks. You’ll also find information about clinical trials, journal articles, and high-risk groups.
Additional reporting by Lauren Bedosky.
Editorial Sources and Fact-Checking
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- Advanced Molecular Detection: Food Safety. CDC. October 15, 2019.
- Whole Genome Sequencing (WGS) Program. FDA. February 14, 2018.
- Listeria: The Listeria Whole Genome Sequencing Project. CDC. May 17, 2016.