Listeria risk factors: who is most at risk from listeriosis

What Listeria infection is

MedlinePlus describes listeriosis as a foodborne illness caused by Listeria monocytogenes, bacteria found in soil and water. It can be in raw foods, processed foods and foods made from unpasteurized milk, and unlike many other germs it can grow even in the cold temperature of the refrigerator (MedlinePlus).

CDC calls the infection rare but serious. It estimates that each year in the United States 1,250 people are infected and 172 people die, making Listeria infection the fourth leading cause of death from foodborne illness (CDC).

Who is most at risk

CDC says Listeria infection can be especially harmful for these groups (CDC):

• Women who are pregnant.
• Newborns.
• People who are 65 years or older.
• People who have a weakened immune system.

Other people can be infected with Listeria, but they usually do not become seriously ill (CDC). MedlinePlus lists the same picture: anyone can get the illness, but it is most likely to affect pregnant women and unborn babies, older adults, and people with weak immune systems (MedlinePlus).

Pregnancy and newborns

CDC says about 1 in 25,000 pregnant women in the United States are infected with Listeria each year. The infection can spread to the baby during pregnancy and cause harm even if the mother does not feel very sick, and 1 in 4 pregnant women who get this illness lose their pregnancy or their baby shortly after birth. CDC adds that early treatment can help save the baby (CDC).

Symptoms in pregnancy are usually mild, and some pregnant women never have symptoms. Even so, CDC says infection during pregnancy usually leads to miscarriage, stillbirth, premature delivery or life-threatening infection of the newborn (CDC). See also our miscarriage risk factors and preterm birth risk factors guides.

Adults 65 and older

More than half of all Listeria infections occur among people 65 years and older. CDC explains that with age the immune system has a harder time recognizing and getting rid of harmful germs, and there is less stomach acid, which can help kill germs. Older adults with Listeria infection almost always have to be hospitalized, and 1 in 6 die (CDC).

A weakened immune system

CDC calls people with a weakened immune system the group most likely to get a Listeria infection: they make up 75% of all people with it, infection almost always leads to hospitalization, and 1 in 6 people in this group die (CDC). CDC says you likely have a weakened immune system if (CDC):

• a healthcare provider told you so
• you have a health condition such as cancer, diabetes, liver or kidney disease, alcoholism, or HIV infection or AIDS
• you are on a treatment that makes it harder for the body to fight off illness, such as steroids or chemotherapy

Related guides: type 2 diabetes risk factors and sepsis risk factors.

Symptoms

CDC describes two kinds of illness (CDC):

• Invasive illness, when Listeria spreads beyond the intestines. Symptoms usually start within 2 weeks after eating contaminated food. In pregnancy they typically include fever and flu-like symptoms such as muscle aches and fatigue. In other people they can also include headache, stiff neck, confusion, loss of balance and seizures. In invasive listeriosis not linked to pregnancy, almost 1 in 6 people die.
• Intestinal illness, with diarrhea and vomiting. Symptoms usually start within 24 hours and last 1 to 3 days. They are usually mild, but some people go on to develop invasive illness.

If you ate food possibly contaminated with Listeria and do not feel sick, CDC says most experts believe you do not need tests or treatment; talk with a healthcare provider if you have questions (CDC).

Safer food choices

CDC advises people in the higher-risk groups, and those who cook for them, to choose safer foods. Examples from its list (CDC):

• Avoid unheated queso fresco-type cheeses (such as queso fresco, queso blanco and requesón) and any cheese made with raw (unpasteurized) milk. Choose hard cheeses or cottage cheese, cream cheese, string cheese, feta and mozzarella made with pasteurized milk, or heat queso fresco-type and raw milk cheeses to 165°F or until steaming hot.
• Avoid unheated deli meat, cold cuts, hot dogs and fermented or dry sausages; reheat them to 165°F or until steaming hot.
• Avoid premade deli salads; choose homemade ones.
• Avoid refrigerated pâté, meat spreads and refrigerated smoked fish; choose shelf-stable sealed versions, or smoked fish cooked in a dish.
• Avoid raw or lightly cooked sprouts; cook them until steaming hot.
• Avoid cut melon left out for more than 2 hours (1 hour above 90°F) or kept in the refrigerator for more than a week.
• Avoid raw (unpasteurized) milk, yogurt and ice cream; choose pasteurized.
• Eat mushrooms, including enoki, only if they are cooked thoroughly.

Everyone can follow the Clean, Separate, Cook and Chill guidelines and keep up with food recalls and outbreaks (CDC). MedlinePlus adds: use precooked and ready-to-eat foods as soon as you can, heat ready-to-eat foods and leftovers until steaming hot, and wash fresh fruits and vegetables (MedlinePlus).

Salmonella is a far more common foodborne germ: CDC estimates it causes about 1.35 million infections in the United States every year (CDC). See salmonella risk factors.

E. coli is another germ spread by contaminated food. Infection with Shiga toxin-producing E. coli (STEC) can lead to hemolytic uremic syndrome (HUS), which can cause kidney failure (CDC). See our E. coli risk factors guide.

Diagnosis and treatment

CDC says Listeria infection is usually diagnosed when a laboratory test grows Listeria from a sample of body fluid or tissue. Invasive illness is treated with antibiotics; most people recover from intestinal illness without them, and people with diarrhea should drink plenty of fluids (CDC).

Common questions

I ate a recalled food. Do I need a test?

If you do not feel sick, CDC says most experts believe you do not need tests or treatment. If you have a fever and other symptoms such as fatigue and muscle aches, contact a healthcare provider and say what you ate, especially if you are pregnant, 65 or older or have a weakened immune system (CDC).

Can Listeria grow in the fridge?

Yes. MedlinePlus says Listeria can grow even in the cold temperature of the refrigerator (MedlinePlus).

Can healthy adults get seriously ill?

Other people can be infected, but CDC says they usually do not become seriously ill (CDC).