Listeriosis is a severe condition that occurs when you eat food that is contaminated with the bacteria known as Listeria monocytogenes.¹ Listeriosis poses a significant threat to public health, particularly for pregnant people, newborns, the elderly, and individuals with weakened immune systems.¹ It is the third most common cause of mortality from food poisoning.² While the symptoms of this food poisoning are similar to the flu, they can progress to meningitis, septicemia, and even miscarriage in pregnant people and death in vulnerable populations.³ Given the potential for significant consequences, the prevention of listeriosis is essential.

You can protect yourself and your loved ones from this serious condition by avoiding consuming high-risk foods and by following a few simple steps in your kitchen! 

Understanding Listeriosis

What causes listeriosis?

The bacteria Listeria monocytogenes are frequently seen in the environment, particularly in soil, groundwater, decomposing plants, and animal and bird feces. Humans can contract these bacteria from the environment, through contact with animals, and through contaminated food products during processing.^1,3 Unfortunately, it is a tough germ that can be hard to get rid of completely from food processing facilities and kitchens, and it can spread to food that comes into contact with infected equipment or surfaces, and even develop on food stored in the refrigerator.^1,3

People at risk

Listeriosis poses a higher risk for certain individuals, including:

• elderly people (>65 years)
• individuals with weakened immune systems, eg: transplant patients, cancer patients, diabetics, kidney disease patients, and HIV/AIDS patients
• pregnant people and their unborn children, resulting in miscarriage, the death of the unborn child, low birth weight babies, neonatal health issues, or even infant mortality
• newborns^1,3

Symptoms

Common symptoms include:

• flu-like symptoms, like fever, chills, and headache
• upset stomach and diarrhoea
• nausea and vomiting
• muscular pains;
• disorientation or loss of balance
• uncontrollably spasming muscles⁴

For particular populations which are at a higher risk of developing Listeriosis, common symptoms include:

• Pregnant people: Patients can suffer from fever and other flu-like symptoms, particularly fatigue and pains in the muscles. 
• Newborns: Fever, vomiting, uncontrollable and constant crying, breathing difficulties, including wheezing, fast breathing, short breaths, and lack of willingness to eat.⁴

A severe listeriosis infection can spread to the bloodstream or brain, potentially causing life-threatening conditions such as sepsis, meningitis, or encephalitis.³

Prevention Strategies 

Since there is no vaccination for listeriosis, prevention is crucial, especially for vulnerable people. You can prevent listeriosis by following these strategies:

Avoiding High-Risk Foods 

Foods that have the Listeria bacterium in them will seem, smell, and taste normal. While listeria can contaminate a variety of meals, it is most frequent in raw foods and chilled ready-to-eat meals.⁵

Therefore, it is crucial for high-risk people in particular to refrain from consuming the following foods:

• foods with a lengthy shelf life that are refrigerated
• foods that are consumed raw without additional processing, like cooking, that could kill Listeria
• soft mold-ripened cheeses, including camembert, brie, queso fresco and blue-veined cheeses
• unpasteurized milk, including items produced with it
• items made from cold meat that are consumed without being heated or cooked, such as cold pre-cooked chicken, salami, processed/fermented meat items, and ham
• pâté or meat spreads
• smoked seafood (e.g. fish, mussels, and oysters)
• raw seafood like sushi
• cooked or chilled seafood, like peeled prawns
• cooked shellfish
• chilled, ready-to-eat dips like tahini, guacamole, pesto, and hummus
• pre-made sandwiches and salads
• fruits and vegetables that have already been chopped or packed, e.g., from supermarkets, and sandwich bars
• raw fruit, vegetables, and herbs as well as beverages like smoothies and juices produced from fresh or frozen fruit and vegetables, if washing processes are not certain
• soft-serve ice-creams
• hot dogs, and fermented or dry sausages
• sprouts (raw or slightly cooked), e.g bean sprouts
• melons^1,6,7

To discover alternative foods suitable for people in high-risk categories, please refer to CDC recommendations.¹ 

Safe Food Handling Practices

• Always use water and soap to wash your hands for 20 seconds prior to and following preparing food, and after cleaning.
• Use running water and a fruit and vegetable wash to thoroughly clean raw fruits and vegetables.
• When handling raw produce, such as raw meat, poultry, fish, and eggs, use different cutting boards, plates, and utensils. 
• After every usage, wash cutting boards, cutlery, and any surfaces that come into contact with food.
• Clean up spills right away. This is especially crucial in order to prevent Listeria from growing and spreading to other items.
• Regularly clean your refrigerator: Use hot water and a little liquid dishwashing detergent to wipe off the interior walls and shelves of your refrigerator, rinse, and pat dry with a fresh cloth or paper towel.
• Anything that spills in the refrigerator should be cleaned up soon, specifically any meat fluids.^2,4,8,9

The FDA recommends:

• Washing surfaces (refrigerator, cutting board, utensils, kitchen surfaces, etc) that might have contact with contaminated food. 
• Disinfecting surfaces with a mix of one gallon of boiling water and one tablespoon of chlorine bleach.
• Pat dry with a fresh, unused cloth or paper towel.⁹

Cooking foods to safe temperatures

The good news is that Listeria may be readily eliminated by cooking your food with a high temperature:

• When cooking, adhere to the instructions that are on the package, if there are any; otherwise, cook or reheat food (even frozen veggies) until it's thoroughly heated through.
• Reheat any leftovers till they are steaming hot. If the leftovers are more than a few days old, throw them out.
• Cook meat and poultry until the fluids run clear and are neither pink nor red.
• To ensure that food is cooked through and evenly, strictly adhere to the instructions provided by the microwave's owner's handbook and rotate the food.
• Make sure to fully boil liquid food items, such as soups, gravies, and sauces.
• Use a food thermometer to ensure safe cooking temperatures: 145°F (or 63°C) for whole meats and fish (with a 3-minute rest), 160°F (or 71°C) for ground meats, 165°F (or 74°C) for poultry, and cook eggs until the yolk is firm.^4,8,9,10

Avoiding cross-contamination 

Avoiding cross-contamination is crucial to preventing the spread of listeriosis:

• Store food that is ready to eat and that is raw apart to prevent cross-contamination.
• Store meat, poultry, fish, and eggs in the refrigerator and keep them apart from all other food items.
• Store cooked food in the refrigerator in a separate section from raw food and cheese.
• Pet owners should wash pet food dishes after meals and keep children, elderly, and immunocompromised individuals away from pet food and pets that may have eaten contaminated food.^3,9

Storage Guidelines 

• Never cook, freeze, or consume food after its expiration date. Foods that are beyond their use-by date may still smell and seem good, but they might be harmful and cause illness.
• Listeria grows more slowly at the room temperatures, so refrigerate food as soon as possible after purchase.
• It is recommended that your freezer be set to 0°F (or -18°C) and your refrigerator to 40°F (or 4°C) or below.
• Use appliance thermometers to ensure your refrigerator is between 38°-40°F (or 3°-4°C) and your freezer is between 0°-2°F (or -18° to -17°C); adjust settings if necessary and recheck after 5-8 hours.
• Eat chilled, ready-to-eat food by the use-by date printed on the packaging. The longer they are kept in the refrigerator, the greater the possibility that Listeria may develop.
• Consume ready-to-eat items within 4 hours of taking them out of the refrigerator.
• Strictly adhere to the label's storage recommendations, especially those for items that have been opened.
• Consume foods that have been opened within two days, even though there are no instructions.^2,8

Properly storing leftovers

• When putting food in the refrigerator, wrap it in foil or plastic wrap, or put it in clean, covered containers or plastic bags. Make sure that items, such as raw meat, do not spill their fluids onto other food items.
• Keep leftovers in the refrigerator in shallow containers as soon as you finish eating.⁴

It is crucial that vulnerable populations be well-informed about the risks associated with listeriosis. In particular pregnant people, the risk of them contracting Listeria is approximately ten times higher than in the general population.

When contaminated food is consumed, bacteria typically cause sickness 1-3 days later. Symptoms, however, can also strike within 20 minutes after infection, or even up to six weeks later.² 

If you exhibit signs of listeriosis, it is essential that you get in contact with a medical professional immediately. The infection can be treated with antibiotics like sulfamethoxazole and ampicillin.⁴

Summary

• Listeriosis is a bacterial infection that occurs if you eat food contaminated with Listeria monocytogenes. 
• It is important to prevent listeriosis, particularly in susceptible groups including the elderly, young children, pregnant women, and those with compromised immune systems.
• Listeriosis can be prevented by avoiding consuming high-risk foods. 
• Other prevention strategies include storing foods at the right temperature, thoroughly washing hands, utensils, and surfaces, cooking foods to safe temperatures and avoiding cross-contamination 
• It is important to contact a healthcare provider if symptoms of listeriosis occur to ensure timely and effective treatment.