HealthSheets™


Understanding Listeria

Listeria is a foodborne illness. It is caused by the bacteria Listeria monocytogenes. These germs are found naturally in the environment, such as in soil and water. But they can sometimes be found in food.

Anyone can become infected with listeria. For most healthy children and adults, the illness will cause abdominal cramps and diarrhea for a few days. But certain groups of people are more likely to get very sick from listeria. These include pregnant women, very young children, and older adults. People with a weak immune system are also at high risk for more serious disease. So are people taking steroid medicines.

How to say it

lis-TEHR-ee-uh

What causes listeria?

Eating foods contaminated with the germ can lead to the illness. Foods that may become contaminated include:

  • Raw or unpasteurized milk

  • Soft cheeses

  • Deli or processed meats

  • Hot dogs

  • Raw vegetables and fruits

Pregnant women who have it may also pass the germ on to their unborn child.

What are the symptoms of listeria?

In otherwise healthy people, symptoms of listeria may start within 24 hours after infection. They often last a few days. They may last longer if the germ has spread more widely through the body. Typical symptoms include:

  • Fever

  • Achiness

  • Headache

  • Diarrhea

  • Nausea

  • Vomiting

If you have a weak immune system, symptoms may not show up for up to 3 months.

If the bacteria become more widespread after several weeks, symptoms may be less noticeable. They may include fever, headache, confusion, fatigue, backache, and muscle and joint pain.

Listeria can infect the brain. This is more likely to happen in people with a weak immune system. This group includes the very young, the very old, pregnant women, and those with cancer. Symptoms of this infection include:

  • Headache

  • Stiff neck

  • Confusion

  • Seizures

  • Tremors

  • Loss of balance or coordination

How is listeria treated?

Most people who have listeria will get better in a few days. Treatment includes:

  • Rest. You may feel better faster if you get plenty of rest.

  • Fluids. Drinking lots of fluids will help you stay hydrated. Don’t drink alcohol or beverages with caffeine.

  • Antibiotics. Several different antibioticscan kill the bacteria in the body. You may need to take these medicines for 2 to 4 weeks, depending on how widespread the infection is. You may need longer treatment if you have a severe case.

When should I call my healthcare provider?

Call your healthcare provider right away if you have any of these:

  • Fever of 100.4°F (38°C) or higher, or as directed

  • You can’t keep a normal amount of fluids because of vomiting

  • Severe weakness or dizziness

  • Sleepiness, confusion, headache, or stiff neck

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