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Listeria (Listeriosis)

Page originally published 5/1/2024.

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Introduction

Listeria, or Listeriosis, is a serious infection. It is usually caused by eating food with the bacterium Listeria monocytogenes. This infection is most likely to sicken:

  • Pregnant women and their newborns,
  • Adults aged 65 or older, and
  • People with weakened immune systems. 

Prevention

Food safety techniques and choosing safer foods can help protect your health.

clean kitchen
  • Keep the kitchen clean.
    • Wash your hands with warm, soapy water before and after handling or preparing food. 
    • After cooking, use hot, soapy water to wash the utensils, cutting board, and other food preparation surfaces.
scrub raw vegetables
  • Scrub raw vegetables with a brush under plenty of running water.
cook food
  • Cook food completely.
    • Use a thermometer to make sure meat, poultry, and egg dishes are cooked to a safe temperature.
choose safer foods
  • Choose safer foods. Pregnant women, adults aged 65 and older, and people with weakened immune systems should not eat:
    • Soft cheeses such as Feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and queso panela, unless they have labels that clearly state they are made from pasteurized milk.
    • Hot dogs, luncheon meats, and deli meats (unless they are heated until steaming hot).
    • Pates or meat spreads from the refrigerated section of the store, or from a deli. Canned meat is not a risk for Listeria.
    • Ready-to-eat cold, smoked, or raw seafood, including nova style, lox, kippered or jerky. Canned seafood is not a risk for Listeria.
    • If you are using any of these products in a casserole or other dish that is cooked completely, these products should be safe to consume.

Symptoms

Signs and symptoms vary based on the person infected and the part of the body affected.  

Listeria can cause intestinal illness. Symptoms may start within 24 hours after eating contaminated food and usually last 1-3 days. Symptoms are usually mild and may include:

  • Diarrhea, and/or
  • Vomiting.

Some people with intestinal illness may develop invasive illness. Invasive illness happens when Listeria have spread beyond the gut (intestines). Symptoms can be severe and usually start within 2 weeks after eating contaminated food. Symptoms may include:

  • Fever;
  • Flu-like symptoms, such as muscle aches and fatigue;
  • Headache;
  • Stiff neck;
  • Confusion;
  • Loss of balance; and/or
  • Seizures.

Invasive illness infection in pregnant people may lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn. 

Diagnosis and Treatment

Listeriosis is usually diagnosed through a blood or spinal fluid test.

Most people recover from intestinal illness without treatment. Though persons that are sick should drink extra fluid while they have diarrhea. Antibiotics are needed only for patients who are very ill or at risk of becoming very ill.

Outbreaks

When two or more people get the same illness from the same contaminated food or drink, that is called a foodborne disease outbreak. Contaminated food or drinks should not be eaten and should be thrown away or returned to the store. Selected multistate outbreaks include:

queso fresco

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