Listeria are bacteria that cause a dangerous foodborne illness called listeriosis. Eating food contaminated with Listeria can cause serious illness, especially in pregnant people and those with weakened immune systems.

According to the Food and Drug Administration (FDA), listeriosis has a 20–30% mortality rate. However, it is rare in comparison with other foodborne illnesses, such as Salmonella.

The following groups of people have a higher risk of complications from Listeria and should be especially careful to prevent listeriosis:

Learn more about listeriosis here.

Learn more about foods to avoid during pregnancy here.

This article will outline some foods that can contain Listeria and provide prevention tips and swaps. It will also cover treatment methods, symptoms, and when a person should contact a doctor.

a person is washing salad leaves in the kitchen sinkShare on Pinterest
Ilona Shorokhova/EyeEm/Getty Images

Microgreens and salads pack a burst of flavor, but they can also harbor bacteria that cause foodborne illness.

Prevention

The Centers for Disease Control and Prevention (CDC) suggest taking the following steps to remove most of the contamination from leafy greens:

  • Wash the hands for 20 seconds with soap and water before and after preparing leafy greens.
  • Remove the outer leaves.
  • Remove any torn or bruised leaves.
  • Rinse the leafy greens under running water and rub the leaves to remove dirt.
  • Dry leafy greens using a clean towel.

Swaps

Instead of:Try:
buying packaged salads made in storesmaking salads at home, avoiding contamination

According to the CDC, recent outbreaks of listeriosis typically involve dairy products and produce.

Unpasteurized, or “raw,” milk can contain Listeria, as can products made from unpasteurized milk.

Dairy products can also become contaminated during processing, regardless of whether they contain pasteurized or unpasteurized milk.

Swaps

Instead of:Try:
eating soft cheeses and unpasteurized milk products, such as:

feta
brie
camembert
blue-veined cheeses
queso fresco
queso blanco
panela
eating hard or processed cheeses, such as:

cream cheese
cottage cheese
mozzarella
soft cheeses made from pasteurized milk



Learn about some non-dairy substitutes here.

Fruit juices can also contain Listeria if they are not pasteurized or heated to a high temperature.

Swaps

Instead of:Try:
drinking unpasteurized, freshly squeezed juicedrinking canned or “from concentrate” juices

The United States Department of Agriculture state that uncooked meat can contain Listeria.

Prevention

Cooking raw meats such as beef, pork, or poultry above a certain temperature can kill bacteria.

The following temperatures for different types of meat can kill Listeria:

Whole meatsGround meatsPoultry
(ground or whole)
Cooking temperature145°F (63°C)160°F (71°C)165°F (74°C)
Standing time3 minutes0 minutes0 minutes

Raw sprouts can also contain Listeria. This is because they grow in warm, moist places where the bacteria can thrive.

Prevention

Thoroughly cooking sprouts will help kill bacteria such as Listeria and Escherichia coli.

Swaps

Instead of:Try:
eating raw sproutseating cooked sprouts or other raw vegetables (washed well)

Eggs that are raw or that a person has not cooked thoroughly enough can also contain Listeria.

Swaps

Instead of:Try:
eating undercooked eggscooking eggs so that the white and the yolk are both solid

Some types of smoked fish are not safe to keep out of the refrigerator. People at high risk should avoid eating fish that they cannot store safely at room temperature.

Prevention

People could use smoked fish as part of another well-cooked dish, such as a casserole.

Swaps

Instead of:Try:
buying smoked fish from a deli counterbuying canned smoked fish

Melons, especially pre-sliced melons, can also contain Listeria. This may be because they have come into contact with the bacteria during processing.

Prevention

People can refrigerate sliced melons to reduce the risk of foodborne illness. They should eat it within a week.

Deli meats and hot dogs can also give a person listeriosis, even if they look as though they do not contain raw meat. This is because they can come into contact with other contaminants.

Prevention

When handling deli meats and hot dogs, people should thoroughly clean all cooking surfaces.

According to the CDC, deli meats are safe to eat for up to 2 weeks in an unopened package if a person keeps them in the refrigerator. They are safe for 3–5 days if the packet is open in the refrigerator.

Individuals at high risk should avoid eating these foods unless they have been cooked thoroughly to 165°F (74°C).

Swaps

Instead of:Try:
eating readymade, cold hot dogs and deli meatscooking the same foods until steaming hot

Unlike other bacteria, Listeria can continue to grow in food — even in cold temperatures.

The FDA recommend getting a refrigerator and freezer thermometer to ensure that foods remain at the correct temperature:

Ideal refrigerator temperatureIdeal freezer temperature
40°F (4°C)0°F (-18°C)

If a person has contracted listeriosis but is otherwise healthy, they may not require treatment. The illness could go away on its own.

In severe cases, doctors may prescribe antibiotics. Antibiotic treatment is most effective at treating listeriosis if a person starts treatment early.

If a person develops a severe infection due to Listeria, a doctor will give them intravenous antibiotics. This is a relatively common treatment option.

Learn more about treating listeriosis here.

It can take a long time for symptoms of the infection to show up. In healthy adults, symptoms can begin from 2 days to 3 weeks after a person has consumed the bacteria.

In healthy people who are not pregnant and do not have a weakened immune system, symptoms usually occur very quickly — within about 24 hours of consuming contaminated food.

Some symptoms of the illness include:

Some people also experience a severe headache or a stiff neck.

In people at high risk, such as older adults over 60 years and people with weakened immune systems, severe symptoms may develop.

These symptoms may include:

During pregnancy and in newborns

According to the CDC, listeriosis in pregnancy can lead to pregnancy loss and stillbirth.

If a newborn contracts listeriosis, it can lead to death.

Pregnant people are 10 times more likely to contract listeriosis than other people.

However, pregnant Hispanic people are 24 times more likely to contract listeriosis than other people. According to the FDA, “This is probably caused by eating traditional soft cheese, such as ‘queso fresco,’ and other traditional foods made with milk that is unpasteurized.”

Pregnant people who suspect that they may have listeriosis should contact a doctor as soon as possible.

According to the FDA, symptoms in pregnant people are often mild.

However, the illness can cause a host of problems for a fetus or newborn. It can also cause pregnancy loss, premature birth, and stillbirth. Up to 30% of newborns with listeriosis die.

People with conditions that limit immune system function and those who are taking medications that suppress the immune system should contact a doctor if they suspect that they have any type of food poisoning.

Older adults over the age of 60 years also have a higher chance of developing complications if they eat food contaminated with Listeria.

Cooking foods at a high temperature, storing them correctly, and washing them correctly can all help prevent listeriosis. A person can also avoid consuming any high risk food altogether.

Older adults, pregnant people, and those with weakened immune systems should be careful about the foods they consume. These individuals are more likely than others to develop a serious infection after consuming foods contaminated with Listeria.

If a person suspects that they have eaten contaminated food and are at high risk of experiencing listeriosis complications, they should contact a doctor.