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Listeria Infections
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Listeria Infections

Listeriosis is a foodborne illness caused by bacteria that can survive in refrigerated environments, posing a particular risk to pregnant women, older adults, and those with weakened immune systems.

Overview

Listeriosis is a foodborne illness caused by Listeria monocytogenes, bacteria found in soil and water. It can be present in a variety of raw foods, processed foods, and products made from unpasteurized milk. Unlike many other germs, Listeria can grow even in the cold temperature of a refrigerator.

Symptoms and Treatment

Symptoms include fever, chills, headache, upset stomach, and vomiting. Treatment is managed with antibiotics.

Risk Reduction

While anyone can contract the illness, it is most likely to affect pregnant women and unborn babies, older adults, and people with weak immune systems. To reduce your risk:

  • Use precooked and ready-to-eat foods as soon as possible.
  • Avoid raw milk and raw milk products.
  • Heat ready-to-eat foods and leftovers until they are steaming hot.
  • Wash fresh fruits and vegetables.
  • Avoid rare meat and refrigerated smoked seafood.

Source: Centers for Disease Control and Prevention

Frequently Asked Questions

The incubation period for listeriosis is variable and can range from a few days to several weeks, with symptoms often appearing up to two months after exposure. This long window makes it difficult to pinpoint the exact source of infection. Early symptoms may resemble the flu, including fever, chills, muscle aches, and gastrointestinal issues like nausea, diarrhea, or constipation. If you are in a high-risk group and develop these symptoms, seek medical attention promptly, as early treatment with antibiotics is crucial.
Pregnant women should strictly avoid unpasteurized milk and soft cheeses made from unpasteurized milk, such as feta, Brie, Camembert, and Mexican-style queso fresco, unless the label explicitly states they are made with pasteurized milk. Other high-risk foods include refrigerated smoked seafood, unless it is an ingredient in a cooked dish, and deli meats or hot dogs that are not reheated until steaming hot. It is also advisable to avoid raw sprouts and unwashed fresh produce, as Listeria can contaminate these items during processing or handling.
While many cases present as a mild, flu-like illness, listeriosis can progress to invasive disease, which is life-threatening. Signs of invasive disease include stiff neck, confusion, seizures, and loss of balance or coordination, indicating the bacteria have spread to the central nervous system. In pregnant women, the infection may not cause severe symptoms in the mother but can lead to miscarriage, stillbirth, or severe infection in the newborn. If you experience these neurological symptoms or are pregnant and have a fever, seek emergency medical care immediately.
Yes, Listeria monocytogenes can grow at refrigerator temperatures, which is why it is a unique food safety concern. To reduce the risk, clean your refrigerator every few months using a solution of one tablespoon of unscented liquid household bleach per gallon of water. Pay special attention to areas where food juices may have dripped, such as shelves and drawers. Additionally, store raw meat, poultry, and seafood on the bottom shelf to prevent their juices from dripping onto ready-to-eat foods below.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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