What is listeriosis?

Listeriosis is a serious infection caused by eating food contaminated with bacteria called Listeria monocytogenes.

Persons with listeriosis usually have:

  • Fever
  • Muscle aches
  • Sometimes nausea or diarrhea

If the infection spreads to the nervous system, the following symptoms may occur:

  • Headache
  • Stiff neck
  • Confusion
  • Loss of balance
  • Convulsions

Who gets listeriosis?

Although listeriosis is uncommon in the United States, anyone can get listeriosis if they eat food contaminated with Listeria bacteria.

Although healthy people may consume contaminated food without becoming ill, certain persons at high risk for infection may get listeriosis after eating food contaminated with even a few bacteria.

People at high risk for infection include:

  • Pregnant Women
    • About one third of listeriosis cases happen during pregnancy.
  • Newborns
    • Newborns are very likely to suffer the serious effects of infection during their mother’s pregnancy.
  • Infants
    • Infants may be stillborn, born with septicemia (bacteria in their blood), or develop meningitis (inflammation of the covering of the brain or spinal cord) very early in life, even if the mother does not have any symptoms.
  • Ill People
    • People with weakened immune systems e.g., people with:
      • Cancer
      • Diabetes
      • Kidney disease
      • AIDS
      • People who are taking glucocorticoids
      • The elderly

How is listeriosis spread?

You get listeriosis by eating food contaminated with Listeria bacteria.

  • Babies can be born with listeriosis if their mothers eat contaminated food during their pregnancy.
  • L. monocytogenes is found in soil and water.
  • Vegetables can become contaminated from the soil or from manure used as fertilizer.
  • Animals can carry the bacteria without appearing ill and can contaminate foods of animal origin, such as meats and dairy products.
  • Listeria has been found in raw foods, such as meat and vegetables, and in processed foods that become contaminated after processing, such as soft cheeses and cold cuts.
  • Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacteria.

How soon after exposure do symptoms appear?

Symptoms have been noted to occur within as few as 3 to as many as 70 days after consumption of a contaminated food, and most commonly within 3 weeks.

How is listeriosis diagnosed?

Listeriosis is diagnosed by a test of the blood or spinal fluid.

What is the treatment for listeriosis?

When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus or newborn. Babies with listeriosis receive the same antibiotics as adults.

Even with prompt treatment, some infections result in death. This is particularly likely in the elderly and in persons with other serious medical problems.

How can listeriosis be prevented?

Listeriosis can be prevented by following guidelines used to prevent other foodborne illnesses:

  • Cook thoroughly raw food from animals, such as beef, pork, or poultry.
  • Wash raw vegetables thoroughly before eating.
  • Keep uncooked meats separate from vegetables and from cooked foods and ready-to-eat foods.
  • Avoid raw (unpasteurized) milk or foods made from raw milk.
  • Wash hands, knives, and cutting boards after handling uncooked foods.

If you are in one of the high-risk categories, the following guidelines are also suggested:

  • Avoid soft cheeses such as feta, Brie, Camembert, blue-veined, and Mexican-style cheese.
    • Hard cheeses, processed cheeses, cream cheese, cottage cheese, or yogurt need not be avoided.
  • Cook until steaming hot all leftover foods or ready-to-eat foods (i.e., hot dogs) before eating.
  • Although the risk of listeriosis associated with foods from deli counters is low, persons at high risk may choose to avoid these foods or thoroughly reheat cold cuts before eating.

Where can I get more information?

Contact your physician or the Southern Nevada Health District, Office of Epidemiology at (702) 759-1300.

Contact Information

(702) 759-1000

Updated on: August 20, 2018

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