Listeria and food poisoning.

Listeriosis is a serious infection, usually caused by eating food contaminated with the bacterium Listeria monocytogenes.

Listeria monocytogenes

  • can survive freezing, drying, heat, and high levels of acid, salinity, and alcohol
  • can grow at standard refrigerator temperature (40F)
    • this could be a problem in ready-to-eat foods that are not cooked before eating

Listeriosis can cause a variety of symptoms

  • depending on the person and part of the body affected
  • Listeria can cause fever and diarrhea, similar to other foodborne germs,
    • but this type of Listeria infection is rarely diagnosed.
  • Symptoms of invasive listeriosis…
    • meaning the bacteria has spread beyond the gut…
      • depends on whether the person is pregnant.

Pregnant women typically experience 

  • only fever and other flu-like symptoms,
    • such as fatigue and muscle aches.

Infections during pregnancy can lead to

  1. miscarriage,
  2. stillbirth,
  3. premature delivery or
  4. life-threatening infection of the newborn.

What are some of the usual foods that contain Listeria?


  • when made with unpasteurized milk (raw milk)
    • is more likely to cause listeriosis than
      • when made with pasteurized milk
  • Although pasteurization of milk kills Listeria,
    • products can still get contaminated
      • if made under unsanitary conditions.


For those at higher risk of listeriosis – pregnant women, older adults, and people with weak immunity:

  • Avoid eating soft cheese unless it is labeled “Made with pasteurized milk.”

RAW SPROUTS grow and sprout under warm and humid conditions.

  • These conditions are also ideal for the growth of bacteria, including Listeria.

For those at higher risk of Listeriosis:

  • Avoid raw or lightly cooked sprouts of any kind (alfalfa, clover, radish, mung bean sprouts etc.).
  • Cook sprouts well. 
  • If you buy a pre-made sandwich, salad, or Asian food, ask to leave out raw sprouts.


  • Eat cut melon right away or
    • keep it refrigerated at 41° F or cooler
      • throw away or compost after 7 days.
  • Throw away or compost cut melon left at room temperature for more than 4 hours.

Hot dogs, pâtés, lunch meats, and cold cuts:

  • Avoid juice from hot dog and lunch meat packages from dripping on
    • other foods, utensils, and food preparation surfaces.
      • Wash hands after handling all meats.
  • Throw away opened packages of hot dogs after 1 week in the refrigerator.
  • Throw away unopened packages of hot dogs after 2 weeks in the refrigerator.

How long can you store lunch and deli meat?

  • Throw away factory-sealed, unopened packages after 2 weeks in the refrigerator.
  • Throw away opened packages and meat sliced at a local deli after 3 to 5 days in the refrigerator.

What should people at higher risk of Listeriosis do? 

  • Avoid eating hot dogs, lunch meats, cold cuts, other deli meats (such as bologna), and fermented or dry sausages unless heated to
    • an internal temperature of 165°F or
      • until steaming hot
        • just before serving.
  • Avoid refrigerated pâté and meat spreads from a deli or meat counter or from the refrigerated section of a store.
    • A safer choice would be:
      • meat spreads and pâté in cans, jars or sealed pouches that do not need refrigeration before opening.
      • Refrigerate these after opening.

Recommendations for people at higher risk of Listeriosis:

  • Avoid cold smoked fish unless they are canned or shelf-stable or in a cooked dish, such as a casserole.

Lastly, avoid raw (unpasteurized) milk and products made from raw milk, including yogurt and ice cream. 

  • Look for the word “pasteurized” on the label.
    • If in doubt about the product, don’t buy it!
  • Keep milk and milk products refrigerated at 40°F or colder.

How do you know when to seek medical help?

In people other than pregnant women:

  • symptoms can include
    • headache
    • stiff neck
    • confusion
    • loss of balance and
    • convulsions
      • in addition to fever and muscle aches.

Again, individuals at higher risk of serious listeriosis include:

  • Pregnant women
    • 10 times more likely than other people to get Listeria infection
  • Adults who are 65 years and older
    • 4 times more likely than other people in the United States to get Listeria infections.
      • More than half of all Listeria infections occur in people 65 and older.
  • People with weak immune systems 
    • People with cancer
      • 10 times more likely than other people to get Listeria infection
    • People on dialysis
      • 50 times more likely than other people to get Listeria infection
    • Treatments that make it more difficult for the body to fight off illness:
      • steroids and chemotherapy…
        • can increase the chance of Listeria infection.

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