Listeriosis

What is listeriosis?

Listeriosis is a disease usually caused by eating food contaminated with the bacteria Listeria monocytogenes. The illness develops when the bacteria get into the blood or other body site.

Who gets listeriosis?

Listeriosis mainly affects pregnant women, newborns, adults aged 65 years or older, and people with weakened immune systems. People without these risk factors sometimes get infected, but they rarely have serious disease.

How is listeriosis spread?

Listeria bacteria are commonly found in the environment, including in soil and water. Domestic and wild animals can become infected, even if they do not develop symptoms. People usually become infected after consuming food that has been contaminated with Listeria like raw milk, soft cheeses, unwashed raw vegetables and fruits, undercooked poultry, or ready-to-eat meats such as deli meats. Listeria can also be transmitted from a pregnant woman to her baby in the womb or during birth. Veterinarians, farmers, and others who work with animals can become infected through direct contact with infected animals.

What are the symptoms of listeriosis?

Pregnant women with listeriosis typically experience fever and mild flu-like symptoms, such as fatigue and muscle aches. Infections during pregnancy, however, can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn. Older adults and people with weakened immune systems can develop a serious blood infection or meningitis (inflammation of the lining of the brain and spinal cord). Symptoms in these cases might include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions. People with healthy immune systems typically experience no symptoms or a mild illness with fever and diarrhea, similar to other foodborne diseases.

How soon after exposure do symptoms appear?

Symptoms of listeriosis generally appear about 1–4 weeks after exposure, but might appear up to 70 days after exposure.

How is listeriosis diagnosed?

Laboratory tests on blood or cerebrospinal fluid are needed to confirm the diagnosis.

What is the treatment for listeriosis?

Listeriosis can be treated with antibiotics. People who are pregnant, aged 65 years or older, or have weakened immune systems and who experience flu-like symptoms within two months of eating food known to be contaminated with Listeria should tell their health care provider about eating the contaminated food. If a person has eaten food known to be contaminated with Listeria and does not have any symptoms, most experts believe that no tests or treatment are needed, even for people at high risk for listeriosis.

How can listeriosis be prevented?

There is no vaccine for listeriosis. People should take the following steps to prevent listeriosis:

  • Avoid raw (unpasteurized) milk, cheese, and other dairy products.
  • Pregnant women and people with weakened immune systems should avoid soft cheeses and avoid or properly heat all leftovers, ready-to-eat foods, hot dogs, deli meats, and other cold cuts.
  • Thoroughly wash raw fruits and vegetables before eating.
  • Keep uncooked meats separate from fruits, vegetables and cooked foods.
  • Thoroughly cook meats and poultry to appropriate temperatures.
  • Wash knives, cutting boards, and kitchen surfaces after contact with uncooked foods.
  • Practice proper handwashing to prevent the bacteria from entering the mouth.
  • Clean the refrigerator regularly, especially after spills from ready-to-eat food packages, raw meat, and raw poultry.

Should an infected person be excluded from work or school?

People who have diarrhea should not work as food handlers, or provide care for children or patients. Children who have diarrhea should not go to child care. Most infected people can return to work or school 24 hours after diarrhea stops, provided that they carefully wash their hands with soap and warm water after using the toilet.

How can I get more information about listeriosis?

September 2018