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About... Listeriosis


What is listeriosis?

Listeriosis (list-ear-ee-OH-sis) is a contagious disease caused by Listeria monocytogenes bacteria. These bacteria are found in soil, untreated water, and the intestines of some animals. These animals are not sick but can pass the bacteria into the soil through manure. Illness can be very serious in pregnant women, newborns, elderly persons, and persons with weakened immune systems. On average, 14 cases of listeriosis are reported in Indiana each year.

How is listeriosis spread?

Most often, people get listeriosis by eating food contaminated with Listeria bacteria. Listeria is killed by pasteurization and cooking. However, in certain ready-to-eat foods, e.g., luncheon meats, contamination may occur after cooking but before packaging. Raw produce may become contaminated by contact with soil or manure. Unlike other bacteria found in food, Listeria can multiply in food even while refrigerated.
Foods at high risk for listeriosis include:

  • Raw vegetables
  • Uncooked meats and seafood
  • Ready-to-eat meats, e.g., refrigerated pâté, , sausage, hot dogs, cold cuts, and deli meats
  • Soft cheeses, e.g., feta, Brie, Camembert, blue-veined, and Mexican-style (queso fresco)
  • Unpasteurized dairy products

Outbreaks of listeriosis have been attributed to unpasteurized dairy products, soft cheeses, raw vegetables, and ready-to-eat meats.

The only way listeriosis can be spread person to person is from mother to baby during pregnancy. It cannot be spread by other person-to-person contact.

What are the symptoms of listeriosis?

  • Fever
  • Headache
  • Muscle aches
  • Nausea
  • Vomiting
  • Abdominal cramps
  • Diarrhea

Symptoms usually begin 21 days (range of 3-70 days) after exposure. Duration of symptoms depends on the health of the infected person; symptoms can last several days or several weeks. Healthy people usually do not have any symptoms, while others may have a mild illness.

Are there complications from listeriosis?

Women who are infected during pregnancy can pass the infection to the fetus or newborn. This can result in miscarriage, premature delivery, stillbirth (fetal death), retardation, and other problems. Death occurs in approximately 30 percent of newborns infected with Listeria.

Sometimes people with listeriosis may develop blood infection (sepsis) or meningitis (infection of the brain and spinal cord). If the infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, seizures, and coma can occur. Even with prompt treatment, some people, such as those with weakened immune systems or the elderly, may die.

How do I know if I have listeriosis?

Persons at higher risk for listeriosis who have unexplained symptoms should consult a health care provider. However, since many persons have no symptoms, it is often unknown if a pregnant woman and her fetus are at risk. There is no routine screening for Listeria in pregnant women. The health care provider may collect several samples to test for Listeria if infection is suspected.

How is listeriosis treated?

Antibiotics are available to treat the infection in all persons, regardless of age. If infection occurs when a woman is pregnant, antibiotics given promptly can often prevent infection of her baby.

Is listeriosis a reportable disease?

Yes. Health care providers or laboratories must report cases of listeriosis to the local health department (LHD) or the Indiana State Department of Health (ISDH) within 72 hours of diagnosis. The LHD will contact all cases diagnosed with Listeria, so a possible exposure can be determined to help prevent others from becoming ill.

How can listeriosis be prevented?

In general, listeriosis can be prevented by strictly adhering to the following guidelines:

  • Practice good hygiene:
    • Thoroughly wash hands with soap and water after using the restroom; after assisting someone with diarrhea and/or vomiting; after contact with animals and reptiles; after swimming; before, during, and after food preparation; and after exposure to raw meat products (please refer to Quick Facts about Hand Washing).
    • Clean food preparation work surfaces, equipment, and utensils with soap and water before, during, and after food preparation, especially after contamination with raw meat products.
  • Separate raw and cooked foods:
    • Avoid cross-contamination by keeping uncooked meat products separate from produce, ready-to-eat foods, and cooked foods.
    • Use separate equipment and utensils to handle raw foods.
  • Maintain safe food temperatures:
    • Ensure proper temperatures are maintained during refrigeration (<40˚F), freezing (<2˚F), holding (keep food hot or at room temperature for no longer than 2 hours), and chilling (chill immediately and separate into smaller containers if needed).
    • Thoroughly cook all food items to USDA recommended safe minimum internal temperatures:
      • 145˚F – steaks, roasts, and fish
      • 160˚F – pork, ground beef, and egg dishes
      • 165˚F – chicken breasts and whole poultry
  • Eat safe foods and drink safe water (Remember: Contaminated foods may look and smell normal):
    • Do not eat undercooked meat, poultry, or eggs.
    • Do not eat foods past the expiration date.
    • Do not eat unpasteurized dairy products. It is illegal to sell unpasteurized dairy products in Indiana.
    • Wash all produce before eating raw or cooking.
    • Use treated water for washing, cooking, and drinking.
  • Handle animals safely:
    • Wash hands after contact with farm animals or petting zoos and contact with pets, especially if they are suffering from diarrhea.
  • Persons at high risk should:
    • Not eat or handle packages of ready-to-eat foods, soft cheeses, and smoked fish.
    • Cook leftover foods or ready-to-eat meat products until steaming hot.
    • Avoid contact with infective materials, such as aborted animal fetuses on farms.

Where can I learn more about listeriosis?

To search Indiana data and statistics:

To search the Indiana Food Protection Program:

To search disease information:

To search for national data, statistics, and outbreaks: 

Updated on January 9, 2009