Listeria

Listeria monocytogenes is a hardy bacterium that causes listeriosis, a rare but serious foodborne infection. Unlike most foodborne germs, it can keep multiplying in refrigerated food.

  • Food safety
  • Germs & illness

Listeria monocytogenes is a disease-causing bacterium found in soil, water, sewage, rotting vegetation and animals. It gets into food when products are harvested, processed, packed, shipped or stored in a contaminated environment, and once it settles into a food plant it is hard to remove completely. Its standout trait is cold tolerance: it survives and slowly multiplies at refrigerator temperatures, so chilling holds it back far less than it holds back most other foodborne bacteria. Thorough heating, by contrast, destroys it easily. Illness ranges from a brief intestinal upset to invasive listeriosis, which spreads beyond the gut.

CDC estimates that Listeria infects about 1,250 people and kills about 172 in the United States each year, making it the fourth leading cause of death from foodborne illness. Those most at risk are pregnant women, newborns, adults 65 and older, and people with weakened immune systems. During pregnancy, infection can lead to miscarriage, stillbirth, premature delivery or a life-threatening infection in the newborn. Because the germ grows in the cold, ready-to-eat foods that sit in a refrigerator for a long time, or in one that runs warm, carry extra risk.

Key facts

U.S. infections per year (CDC estimate)
About 1,250
U.S. deaths per year (CDC estimate)
About 172
Intestinal illness onset
Usually within 24 hours; lasts 1–3 days
Invasive illness onset
Usually within 2 weeks of eating contaminated food

In a bakery or commercial kitchen

  • Keep refrigerators at 40°F (4°C) or colder and freezers at 0°F (-18°C), and verify both with thermometers
  • Clean and sanitize surfaces, equipment and cutting boards, and pair that routine with firm time and temperature controls
  • Rotate refrigerated ready-to-eat items quickly, since long cold storage gives Listeria time to multiply
  • Set up environmental monitoring if exposed ready-to-eat foods face an environmental pathogen hazard; FDA suggests testing for Listeria species
  • Contact your local health department if you handled recalled or possibly contaminated food, and let exposed customers know

For home and cottage bakers

  • Keep the refrigerator at 40°F or below and the freezer at 0°F, checked with an appliance thermometer
  • Eat refrigerated ready-to-eat and precooked foods soon instead of storing them for long stretches
  • If you are pregnant, 65 or older, or immunocompromised, heat deli meats and hot dogs to 165°F or until steaming
  • Choose dairy products made with pasteurized milk, and contact a healthcare provider if you are worried about an exposure

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 17, 2026.

  1. About Listeria Infection, Centers for Disease Control and Prevention
  2. Symptoms of Listeria Infection, Centers for Disease Control and Prevention
  3. Preventing Listeria Infection, Centers for Disease Control and Prevention
  4. Listeria (Listeriosis), U.S. Food and Drug Administration
  5. Listeria monocytogenes Risk Assessment: Questions and Answers, U.S. Food and Drug Administration