Understanding Listeria: Risks, Symptoms, and Prevention

You may know the term listeria from the recent Boar’s Head brand liverwurst outbreak. Other than the fact that listeria is bad, most people don’t really know what it means, so this article aims to explain what listeria is, its signs and symptoms, and ways to help reduce your risk.  

The Listeria Bacteria: Where It Lives and How It Spreads 

Listeria is a disease-causing bacteria found in various environments like soil, water, and decaying vegetation and animals. It is tricky because it can grow under refrigeration and other food preservation measures. People typically get sick when they eat food contaminated with Listeria monocytogenes (L. monocytogenes) and develop a disease called listeriosis. Typically, it is spread when foods are contaminated with L. monocytogenes during harvest, processing, preparation, packing, transportation, or storage. Pets can also spread the bacteria in the home if they eat food contaminated with L. monocytogenes. 

Who Is at Risk: Understanding Vulnerability to Listeriosis 

Listeriosis can be especially dangerous for not only the elderly and people with weakened immune systems but it can be particularly dangerous for pregnant women and their babies. Listeriosis during pregnancy can sometimes lead to miscarriage or stillbirth. Those babies born with listeriosis infection may develop severe health complications, lifelong health problems, or result in death. 

Symptoms of Listeriosis: Recognizing the Signs 

Symptoms of listeriosis can range from mild to severe, and depending on the severity of the illness, symptoms may last from days to several weeks. Mild symptoms can often be mistaken for the flu, including fever, muscle aches, nausea, vomiting, and diarrhea. Severe symptoms of listeriosis include headache, stiff neck, confusion, loss of balance, and convulsions. For the elderly, very young, and immune-compromised, listeriosis can even result in death. 

Once infected with L. monocytogenes, symptoms can appear as soon as a few hours after eating contaminated foods or as long as two to three days. Shockingly, the more severe forms of listeriosis can take a few days to three months to develop. 

High-Risk Foods: Identifying Potential Sources of Listeria 

Foods that have been linked to previous listeriosis outbreaks in the United States include raw and unpasteurized milks and cheeses (especially certain soft cheeses like queso fresco), ice cream, deli meats, hot dogs, raw or processed vegetables, raw or processed fruits, raw or undercooked poultry, sausages, and raw or smoked fish and other seafood. Listeriosis can also be found in ready-to-eat foods. 

There are several things you can do to protect yourself from contamination. Ensure your refrigerator is set to 40 degrees Fahrenheit and your freezer is set to 0 degrees Fahrenheit. This will help slow down or prevent the growth of L. monocytogenes. However, it is important to know that refrigeration and freezing foods will not completely eliminate L. monocytogenes if that food is contaminated. Other ways to protect yourself are by cleaning the walls and shelves of your refrigerator often and cleaning cutting boards, countertops, and any utensils that may have contact with contaminated foods. 

When handling foods, washing your hands with warm water and soap for at least 20 seconds before and after touching foods is important. It is also important to wash your fruits and vegetables and separate raw meats to avoid cross-contamination. Ensure you cook your food to a safe internal temperature using this chart for reference. 

A few things to keep in mind for pregnant women wanting to prevent listeriosis are avoiding unpasteurized or raw milk, cheeses made from unpasteurized milk, raw fish, and raw sprouts. The FDA recommends that pregnant women thoroughly heat hotdogs and lunch meat prior to eating to help reduce their risk of listeriosis.

1. _{Food Safety and Inspection Service. Safe Minimum Internal Temperature Chart | Food Safety and Inspection Service. (n.d.). https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/safe-temperature-chart}  
2. _{Program, H. F. (n.d.). Listeria (listeriosis). U.S. Food and Drug Administration. https://www.fda.gov/food/foodborne-pathogens/listeria-listeriosis}  
3. _{Program, H. F. (n.d.). What you need to know about preventing listeria infections. U.S. Food and Drug Administration. https://www.fda.gov/food/buy-store-serve-safe-food/what-you-need-know-about-preventing-listeria-infections}