Listeria or Listeriosis

What is Listeria?

Listeria Monocytogenes is the germ that has been at the center of a recent nationwide food-related outbreak. Listeria, like other bacteria, is found in the environment like soil, vegetation, animal feed, and in human and animal feces. Animals and humans can carry the bacterium without knowing it. Just like with other foodborne illnesses or “food poisoning”, Listeriosis occurs when one eats food contaminated by this bacterium. However, unlike most bacteria, Listeria can survive and sometimes grow on foods stored in the refrigerator. Foods that are contaminated with Listeria, look, smell and taste normal. Listeria can be killed by proper cooking procedures.

The symptoms of Listeriosis

The symptoms may vary from very mild to severe(in high-risk individuals). In general, they include:

  • Nausea and/or vomiting
  • Abdominal cramps
  • Diarrhea
  • Severe headache
  • Fever

The symptoms usually appear within 2 to 30 days after eating contaminated food. In some cases, this period can be as long as 70 days after ingestion.

Persons who are at the highest risk include:

  • Pregnant women are about 20 times more likely to get Listeriosis than other healthy adults. Listeriosis during the first three months of pregnancy may result in a miscarriage. Later on, in pregnancy, the infection can result in a stillbirth or the birth of an ill, infected baby.
  • Newborns
  • The elderly
  • Persons with weak immune systems

Listeriosis in high-risk people can result in severe infections of the brain and its covering (meningitis), infection of the blood, and tragically even death.


Death is very rare, and in most cases, the infection can be treated effectively with antibiotics. The earlier the diagnosis is made, the more successful the treatment, especially for those at high risk.

Prevention of Listeriosis

Health Canada has the following recommendations that also apply to the prevention of other foodborne infections:

  • Read and follow all package labels and instructions on food preparation and storage
  • After handling foods, especially raw meat and fish, thoroughly clean and sanitize all surfaces used for food preparation with a kitchen sanitizer (following the directions on the container) or use a bleach solution (5 ml household bleach to 750 ml of water), and rinse with water.
  • To avoid spreading bacteria, clean all knives, cutting boards, and utensils used with raw food before using them again.
  • Thoroughly clean fruits and vegetables before you eat them.
  • Refrigerate or freeze perishable food, prepared food, and leftovers within two hours.
  • Defrost food in the refrigerator, in cold water, or in the microwave, but never at room temperature.
  • Keep leftovers for a maximum of four days and reheat them to an internal temperature of 74°C (165°F) before eating them.
  • Check the refrigerator temperature with a thermometer to make sure it is at 4°C (40°F) or below. As the fridge temperature increases, so do the growth of Listeria in foods.
  • Frequently wash and disinfect the refrigerator. The more often it is cleaned, the less chance there will be for Listeria to be transferred from contaminated food and surfaces to non-contaminated foods.

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Pediatrician DR.PAUL Roumeliotis is certified by the American Board of Pediatrics and Royal College of Physicians and Surgeons of Canada. The information provided above is designed to be an educational aid only. It is not intended to replace the advice and care of your child’s physician, nor is it intended to be used for medical diagnosis or treatment. If you suspect that your child has a medical condition always consult a physician.