Listeriosis in Leftovers?

With the changing of seasons and Holiday’s right around the corner, you may soon find your fridge stocked to the brim. Your favorite restaurants are closed for the off season. Teton County is slowing down from a crazy summer, and on top of that it’s cold outside! If you’re anything like me, now is the best time to prepare your most favorite meals in the comfort of your own home. So, what can you find in your fridge? At my house, you will find raw meat and poultry, unwashed vegetables, dairy products and deli meats. Now go ahead, take a look inside your refrigerator.

What you may not notice is what’s lurking inside of your ingredients and leftovers: the bacterium Listeria monocytogenes which, when ingested, can cause a serious illness known as Listeriosis. It is estimated that 1,600 individuals are infected each year, and about 260 of those infections result in death ( The older the food in your refrigerator, the higher the chance of this harmful bacteria growing. What’s worse is that Listeria can grow on refrigerated foods!

What is Listeria Monocytogenes?

Listeria is a species of disease-causing bacteria that can be found in moist environments, water, soil, decaying vegetation and animals. It is transmitted to food when it’s harvested, processed, prepared, packaged, transported, or stored in contaminated environments. Associated foods include raw meat and poultry, fresh soft cheese, paté, smoked seafood, deli meats and deli salads. Listeriosis has a 20-30% mortality rate; fortunately for us this illness is rare but can be very serious.

What are the symptoms and treatment?

Depending on the severity of the illness, symptoms may last from days to several weeks. Symptoms may include fever, muscle aches, nausea, vomiting and diarrhea. As the sickness becomes more severe you may experience headache, stiff neck, confusion, loss of balance, and convulsions. The sickness is most likely to affect individuals who are immunocompromised: pregnant women and their newborns, adults aged 65 or older, children, and those with weakened immune systems. Symptoms usually don’t start for 1-4 weeks after eating contaminated foods and some people have reported symptoms starting as late as 70 days after exposure! Listeriosis can be treated with antibiotics.

How can I prevent Listeriosis?

  1. Chill at the right temperature. Put a thermometer in the refrigerator and adjust the temperature control as necessary. Your refrigerator should register at 41°F (4°C) or below and your freezer at 0°F (-18°C). 
  2. Use ready-to-eat foods quickly! Listeria has a higher chance of growing if food is stored in the refrigerator for long periods of time.  Use ready-to-eat, refrigerated foods by the Use-By Date on the package labeling. If your food is homemade, eat or throw it away within 7 days.
  3. Keep the refrigerator clean. Wipe up spills immediately. Clean the inside walls and shelves with hot water and liquid dish wash detergent. Rinse and let air dry.

Take Away:

L. Monocytogenes is a bacteria found in the natural environment that can contaminate foods sometime between processing and landing on your table. Listeria causes serious illness, especially in the immunocompromised. You can easily prevent sickness by keeping refrigerated foods at 41°F (4°F) or lower, eating food in a timely manner, and keeping your refrigerator clean. It is especially important to know the age of the foods in your refrigerator. The expiration dates on package labels are an important date to note. If you have homemade food stored in your refrigerator, all leftovers should be eaten or thrown out within 7 days.

Helpful Links:

Listeria infographic