Listeriosis

What is listeriosis?

Listeriosis is a disease usually caused by eating food contaminated with the bacteria Listeria monocytogenes. Invasive illness develops when the bacteria get into the blood or other sterile body sites (areas where microorganisms are not typically found).

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 become seriously ill.

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, pate (meat spreads), cold smoked fish, 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. However, infections during pregnancy can sometimes lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn. Other people, including 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 mild illness, such as fever and diarrhea, which are 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 (CSF) are needed to confirm the diagnosis for invasive disease. Milder illness (vomiting, diarrhea) is rarely diagnosed because laboratories do not regularly test patients with these types of samples (stool).

What is the treatment for listeriosis?

Listeriosis can be treated with antibiotics. People, especially those 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. Talk with a healthcare provider if you have questions about what to do.

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 properly reheat all leftovers, ready-to-eat foods, hot dogs, deli meats, refrigerated pates (meat spreads), refrigerated smoked fish, premade deli salads, raw or lightly cooked spouts, cut melon left out for more than two hours or left in the fridge for more than a week, and other cold cuts to an internal temperature of 165°F or until steaming hot to kill any germs.
• 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 with hot soapy water after contact with uncooked foods.
• Wash hands for at least 20 seconds with soap and warm or cold water before, during, and after preparing food and before eating.
• Clean the refrigerator regularly, especially after spills from ready-to-eat food packages, raw meat, and raw poultry.

Should a sick 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 childcare. 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 or cold water after using the bathroom.

How can I get more information about listeriosis?

• If you have concerns about listeriosis, contact your healthcare provider.
• Call your local health department. You can find your local health department at vdh.virginia.gov/health-department-locator/.
• Visit the CDC page on listeriosis at cdc.gov/listeria/index.html for more information.