What is Listeriosis?

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Listeriosis is a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes. An estimated 1,600 people get listeriosis each year, and about 260 die. The infection is most likely to sicken pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems.

Signs and symptoms of Listeria infection vary depending on the person infected and the part of the body affected.

The bacteria are most likely to sicken people who are pregnant and their newborns, adults aged 65 or older, and people with weakened immune systems. Other people can be infected with Listeria, but they rarely become seriously ill.

Invasive illness

Invasive means bacteria have spread beyond the intestines (gut). Invasive listeriosis happens when Listeria have spread beyond the intestines.

Symptoms of invasive illness usually start within 2 weeks after eating food contaminated with Listeria.

Symptoms of invasive illness

People who are pregnant

Symptoms typically include

  • Fever
  • Flu-like symptoms, such as muscle aches and fatigue

People who are not pregnant

Symptoms typically include

  • Fever
  • Flu-like symptoms, such as muscle aches and fatigue
  • Headache
  • Stiff neck
  • Confusion
  • Loss of balance
  • Seizures

Severity of invasive illness

People who are pregnant

  • Symptoms in pregnant people are usually mild. Some pregnant people never have symptoms.
  • However, infection during pregnancy usually leads to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.

People who are not pregnant

  • Symptoms in non-pregnant people can be severe.
  • Almost 1 in 20 non-pregnant people with invasive listeriosis die.

Intestinal illness

Listeria can also cause an intestinal illness. This kind of illness is rarely diagnosed because laboratories do not regularly test patient stool (poop) samples for Listeria.

Symptoms of intestinal illness usually start within 24 hours after eating food contaminated with Listeria and usually last 1–3 days.

Symptoms of intestinal illness

Symptoms typically include

  • Diarrhea
  • Vomiting

Severity of intestinal illness

  • Symptoms are usually mild.
  • However, some people with intestinal illness develop invasive illness.

Diagnosis and Treatment

Listeriosis is usually diagnosed when a bacterial culture (a type of laboratory test) grows Listeria from a body tissue or fluid, such as blood, spinal fluid, or the placenta.

Treatment

Invasive illness: People with an invasive illness are treated with antibiotics. 

Intestinal illness: Most people recover from intestinal illness without antibiotic treatment. Antibiotics are needed only for patients who are very ill or at risk of becoming very ill. People who have an intestinal illness should drink extra fluids while they have diarrhea.

Prevent Listeria

Listeria is a harmful germ that can be in food. Find out which foods are more likely to be contaminated with Listeria and ways you can protect your health and the health of your loved ones.

Choose safer foods

Listeria is especially harmful for some people:

If you are in any of these groups, choose safer foods to protect your health or your pregnancy:

Do not eat Choose these instead

Eat this, not that

• Unpasteurized soft cheeses, such as queso fresco and brie

•Unheated cheeses sliced at a deli

 • Hard cheeses, such as cheddar and parmesan

•Cottage cheese, cream cheese, string cheese, feta, and mozzarella

•Pasteurized soft cheeses heated to an internal temperature of 165°F or until steaming hot

•Deli-sliced cheeses heated to 165°F or until steaming hot
• Unheated deli meat, cold cuts, hot dogs, and fermented or dry sausages • Deli meat, cold cuts, hot dogs, and fermented or dry sausages reheated to 165°F or until steaming hot
• Premade deli salads, such as coleslaw and potato, tuna, or chicken salad • Homemade deli salads
• Refrigerated pâté or meat spreads • Pâté or meat spreads in sealed, airtight containers that don’t need to be kept refrigerated before opening
• Refrigerated smoked fish • Smoked fish in sealed, airtight packages or containers that don’t need to be kept refrigerated before opening

•Smoked fish cooked in a casserole or other cooked dishes
• Raw or lightly cooked sprouts • Sprouts cooked until steaming hot
• Cut melon left out for more than 2 hours (1 hour if it’s exposed to temperatures hotter than 90°F, such as a picnic or hot car)

•Cut melon in refrigerator for more than a week

 • Melon that has just been cut
• Raw (unpasteurized) milk, yogurt, and ice cream • Pasteurized milk, yogurt, and ice cream

Because of recent outbreaks, CDC is currently working to understand the risk of Listeria infection from enoki mushrooms. While this work is happening, CDC advises people who are pregnant, aged 65 or older, or have a weakened immune system to not eat raw enoki mushrooms. Instead, cook enoki mushrooms thoroughly, and ask that restaurants cook them thoroughly.

Foods more likely to be contaminated with Listeria

Listeria is a hardy germ that can be difficult to fully remove from food processing facilities. If a facility has Listeria germs, the germs can spread to food that touches contaminated equipment or surfaces. Listeria can also spread from contaminated food to surfaces. It can even grow on foods kept in the refrigerator. The good news is that Listeria is easily killed by heating food to a high enough temperature.

Find out why some foods are more likely to be contaminated with Listeria and learn about recent outbreaks linked to these foods.

Soft cheeses, such as queso fresco and brie

Soft cheeses are more likely than hard cheeses to be contaminated with Listeria because of their high moisture, low salt content, and low acidity. These conditions support the growth of Listeria. Soft cheeses made with unpasteurized milk or made in facilities with unclean conditions are even more likely to be contaminated. Although pasteurizing milk kills germs, cheese made with pasteurized milk can still get contaminated during cheese-making.

Soft cheeses include queso fresco, queso blanco, queso panela, brie, camembert, and blue-veined.

Hard cheeses include asiago, cheddar, emmental, gruyere, parmesan, and swiss cheese.

Meats, cheeses, and salads from the deli

Products sold at the deli, especially those sliced or prepared at the deli, can be contaminated with Listeria. Listeria spreads easily among deli equipment, surfaces, hands, and food. Deli products are kept refrigerated, but refrigeration does not kill Listeria.

Examples of deli salads include coleslaw, potato salad, tuna salad, and chicken salad.

Deli meats, cold cuts, hot dogs, and fermented or dry sausages

Deli meats, cold cuts, hot dogs, and fermented or dry sausages can be contaminated with Listeria when they are made or prepared at facilities where Listeria persists. Although cooking, fermenting, or drying kills germs, these meats can get contaminated afterwards if they touch surfaces with Listeria. Refrigeration does not kill Listeria, but reheating before eating will kill any germs that may be on these meats.

Examples of fermented or dry sausages include chorizo, pepperoni, salami, and summer sausage.

Pâté or meat spreads

Refrigerated pâté or meat spreads can become contaminated with Listeria when they are made in a facility where Listeria persists. Refrigeration does not kill Listeria.

A safer choice is “shelf-stable

” pâté or meat spreads. These are heat-treated to kill any germs and sealed in airtight containers (such as cans, tins, or glass jars). They don’t need to be refrigerated before opening.

Cold-smoked fish

Cold-smoked fish can become contaminated with Listeria when it is made in a facility where Listeria persists. The cold-smoking process does not kill Listeria. Refrigeration also does not kill Listeria.

Safer choices are “shelf-stable

” smoked fish or cooked smoked fish. Shelf-stable smoked fish are heat-treated to kill any germs and sealed in airtight containers or packages that don’t need to be refrigerated before opening. Cooking smoked fish also kills any germs that may be in it.

Cold-smoked fish products are often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.”

Sprouts

Sprouts need warm and humid conditions to grow. These conditions are also ideal for the growth of Listeria and other harmful germs. Germs can grow on the inside and outside of sprouts, so washing them does not remove all germs. Homegrown sprouts can also have germs because they need the same conditions to grow.

Melons

Melons are more likely than many other fruits to be contaminated with Listeria. This is because they have low acidity and can be kept in the refrigerator for a long time. Both these conditions support the growth of Listeria.

Raw (unpasteurized) milk and raw milk products

Raw milk is milk that has not been pasteurized. Pasteurization heats milk to a high enough temperature for a long enough time to kill germs that can make you sick.

Raw milk and products made from it – including ice cream and yogurt – can contain Listeria and other harmful germs. These germs can get into raw milk in multiple ways, including unclean conditions at the dairy farm and contact with animal poop.

CDC recommends that everyone choose pasteurized milk and dairy products.

People at Risk

CDC estimates that Listeria is the third leading cause of death from foodborne illness, or food poisoning, in the United States. An estimated 1,600 people get sick from Listeria each year, and about 260 die.

Listeria is most likely to sicken pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems. Other people can be infected with Listeria, but they rarely become seriously ill.

Who has a greater chance of Listeria infection?

Pregnant Hispanic women are 24 times more likely than the general population to get Listeria infection.

Las mujeres hispanas embarazadas tienen 24 veces mayor que la población general de contraer la infección por Listeria.