What is Listeria?

Listeria is a type of bacteria that can contaminate food and cause illness.

Unlike other foodborne illness causing bacteria, Listeria thrives in cool, and damp environments.  

Listeria is persistent and grows in cool temperatures, even as low as 31 degrees F. When food comes into contact with surfaces that are contaminated with Listeria, the bacteria can grow rapidly on the food despite aggressive cleaning and sanitizing. Listeria can contaminate luncheon meats like hot dogs, cold cuts, and dry sausages. Listeria may also be found in unpasteurized (raw) milk, soft cheeses, smoked seafood, and salads, such as ham salad, chicken salad, or seafood salad. Lastly, Listeria can also be present in soil and can contaminate raw vegetables and fruits.

What is listeriosis?

Listeriosis is the illness caused by Listeria. If people eat foods contaminated with Listeria monocytogenes, they can get sick with listeriosis. Infection can be serious. It is most likely to sicken pregnant people and their newborns, adults aged 65 or older, and people with weakened immune systems. It is rare for people in other groups to get seriously ill with listeriosis. According to the CDC, roughly 1,600 people contract listeriosis each year, and approximately 260 die from the illness.

What are the symptoms of listeriosis?

The symptoms of listeriosis are diverse and range from mild to serious. Listeriosis is especially dangerous for at-risk groups such as pregnant people and their unborn babies, newborns, older adults, those with weakened immune systems. People receiving some medical treatments, such as chemotherapy for treatment of cancer, are at high risk.

Symptoms in people with invasive listeriosis, meaning the bacteria has spread beyond the gut, depend on whether the person is pregnant.

Pregnant people typically experience only fever and other flu-like symptoms, such as fatigue and muscle aches. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn. People who are not pregnant may experience symptoms that include headache, stiff neck, confusion, loss of balance, and convulsions, in addition to fever and muscle aches.

Gastrointestinal symptoms usually appear within a few hours to 2 to 3 days but can sometimes appear 2 to 6 weeks after eating the contaminated food. In some cases, it may take up to 2 months for symptoms to appear. In healthy individuals, listeriosis typically causes mild symptoms which last for only a few days. Listeriosis can also cause death in people with weakened immune systems and the elderly.

Contact your healthcare provider if you’re experiencing one or more of the mentioned symptoms, and suspect you’ve eaten food that was possibly contaminated with Listeria within the past 2 months.

How can you prevent listeriosis?

Fortunately, listeriosis can be prevented by following the steps below:

• Wash hands for 20 seconds with soap and water before preparing and handling food.
• Keep your refrigerator sanitary. Clean up any spills or food left sitting on the shelves or walls of your refrigerator.
• Clean and sanitize any surfaces, such as tabletops, that food may touch.
• Consider using paper towels to clean kitchen surfaces. If you use cloth towels, wash them often in the hot cycle of a washing machine.
• Never drink raw milk or soft cheeses made with unpasteurized milk.
• Separate deli meats from raw meat and poultry products and their juices, so that they do not become contaminated. 
• Keep deli meats refrigerated below 40 degrees F.  Once they are opened, use or freeze within 3-5 days

The following groups are at higher risk of getting very sick from Listeriosis: Pregnant mothers, people with weakened immune systems and adults 65 years old or older. Those who belong to the groups mentioned above should avoid eating the following:

• Deli meats and hot dogs that haven’t been heated to an internal temperature of 165 degrees F.
• Refrigerated smoked seafood that isn’t canned, shelf-stable or fully cooked.
• Sprouts that are not fully cooked.
• Any soft cheeses that aren’t made with pasteurized milk.

Lastly, everyone should remember the four steps to food safety: clean, separate, cook and chill:

• Clean—Always wash your hands with soap and water for at least 20 seconds before and after handling raw meat and poultry.
• Separate—Use separate cutting boards, plates and utensils to avoid cross-contamination between raw meat or poultry and foods that are ready to eat. When cooking and preparing multiple foods, it can be easy to spread bacteria throughout your kitchen.
• Cook—Confirm your meat and poultry products are cooked to a safe internal temperature by using a food thermometer.
• Chill—foods promptly if not consuming immediately after cooking. Do not leave food at room temperature for longer than two hours.

Reference:
CDC’s Website: Listeria (Listeriosis)