Health Library

What Are Listeria Infections?

Listeria is a bacteria (type of germ). Listeria (liss-TEER-ee-uh) infections cause diarrhea, vomiting, fever, and joint pain. Usually, these problems get better in a few days. But an infection can cause more serious problems during a pregnancy, and in newborns, adults over 65 years old, and anyone with a weak immune system (such as people getting chemotherapy).

How Do People Get Listeria Infections?

Listeria infection (or listeriosis) is a type of food poisoning. It happens because someone ate or drank something with the bacteria in it.

The bacteria live mainly in soil (dirt), but are also found in animals, water, and other places. Most Listeria infections happen when people:

• Eat meat or dairy products from infected animals.
• Eat foods that touched something with the bacteria on it (for example, deli meat that touched the bacteria on a surface during processing).
• Drink unpasteurized (raw) milk or eat dairy products made from raw milk.
• Eat vegetables with the bacteria on them from soil.

The infections don’t spread from person to person. For reasons that aren’t clear, Listeria infections are more common in pregnant women, who can pass the infection to their unborn baby.

What Are the Signs & Symptoms of Listeria Infections?

In a person with a healthy immune system, a Listeria infection causes fever, vomiting, diarrhea, and joint pain.

People with a weak immune system and those over age 65 can have more serious problems like bacteremia (infection in the blood) and meningitis (infection around the brain). Pregnant women may only have mild symptoms, but the infection can cause preterm (early) labor, miscarriage, or stillbirth.

How Are Listeria Infections Diagnosed?

Doctors will do an exam and ask about symptoms and what someone ate. Sometimes, they suspect a Listeria infection when other people who live in the same area or ate the same food are infected.

Listeria bacteria don’t usually show up in stool tests, so doctors don’t usually get that test unless they are looking for other infections. Sometimes they order other tests, such as blood tests to check for bacteremia, a spinal tap to check for meningitis, or tests of the placenta to see if someone was infected during pregnancy.

How Are Listeria Infections Treated?

Healthy kids, teens, and adults with a Listeria infection should drink lots of fluids so that they don’t get dehydrated. They should also rest as needed. Don’t give anti-diarrhea medicines, as some can make the diarrhea worse.

Doctors may prescribe antibiotics for people at risk for more serious problems from a Listeria infection. They’ll get the medicine through an IV.

Can Listeria Infections Be Prevented?

Some food safety precautions can help prevent Listeria infections. To help protect your family:

• Cook poultry, meat, and seafood until they are well done.
• Cook eggs until the yolk is firm.
• Make sure all milk products are pasteurized.
• Put leftovers in the refrigerator within 2 hours and use within 3–4 days.
• Reheat cooked leftovers until they are steaming hot.
• Wash fruits and vegetables before eating.
• Eat melon soon after cutting or refrigerate it. Throw away cut melon that has been out at room temperature for more than 4 hours or in the refrigerator for more than 7 days.
• Wash all cutting boards, utensils, and counters that have touched raw poultry or meat, hot dogs, or deli meats. 
• Keep your refrigerator at 40°F or lower and your freezer at 0°F or lower.

If you are pregnant or in another high-risk group, talk to your doctor about other ways to reduce your risk of getting this infection.

When Should I Call the Doctor?

Call your doctor if your child has diarrhea for more than a week or has:

• a fever
• vomiting
• diarrhea with blood in it
• signs of dehydration, such as peeing less often, a dry mouth, few or no tears, or sunken eyes
• extreme sleepiness

You know your child best. Call the doctor if your child has any other signs that concern you.