Listeria infections (known as listeriosis) are caused by the bacterium Listeria monocytogenes.

Infection is uncommon, but when it does occur it most frequently affects pregnant women in their last trimester, newborns, and kids and adults whose immunity is weakened by diseases such as cancer or HIV. People who have had various types of transplants are also more at risk for listeriosis.

Listeria bacteria can be transmitted through soil and water. A person can also ingest listeria by eating certain foods, such as deli meats and cold cuts, soft-ripened cheese, milk, undercooked chicken, uncooked hot dogs, shellfish, and coleslaw made from contaminated cabbage. Many cases of infection, however, have no identifiable source.

Listeria infections may create symptoms such as fever, vomiting, diarrhea, lethargy, difficulty breathing, and poor feeding. Pregnant women who develop listeriosis may experience only mild flu-like symptoms, but they are at risk for premature delivery, miscarriage, and stillbirth.

Listeria can cause a wide range of infections, including gastroenteritis (vomiting and diarrhea also called the "stomach flu"), bacteremia (bacterial infection in the blood), meningitis, pneumonia, osteomyelitis (infection in the bone), and endocarditis.

People who have weakened immune systems are at particular risk for developing the more serious illnesses from listeriosis, including pneumonia, meningitis, and sepsis.

Cases of listeriosis are relatively uncommon. The earlier listeriosis is detected and treated, the better, since it can cause serious and life-threatening infection. And particularly if you are pregnant or in one of the other high-risk groups, avoiding certain foods and beverages can reduce your risk of contracting this infection.

Treating Listeriosis

Listeriosis is usually treated with antibiotics administered in the hospital through an intravenous catheter (IV). Typically, treatment lasts for about 10 days but that can vary depending on the body's ability to fight off the infection.

Children whose immune systems are compromised by illness or infection, such as cancer or HIV, are more likely to develop severe listeriosis infections and may require additional treatment.

In healthy individuals with gastroenteritis due to Listeria, the symptoms often last only 2 days and the person recovers completely.

Preventing Listeriosis

Although there are no vaccines against the bacteria that cause listeriosis, you can help reduce the risk for your family by taking these food safety precautions:

• Always cook food (especially meat and eggs) thoroughly to the proper internal temperature.
• Wash fruits and vegetables thoroughly before eating.
• Only drink pasteurized milk, and make sure that milk is refrigerated at the appropriate temperature, which is less than 40°F (4°C).
• Avoid foods made from unpasteurized milk.
• If you're in a high-risk group, avoid soft cheeses such as feta, Brie, Camembert, blue-veined and Mexican-style cheeses unless they have labels that clearly state they are made from pasteurized milk.
• Reheat precooked, prepackaged foods — such as deli meats or hot dogs — to steaming hot temperatures, especially if you're pregnant.
• Carefully wash hands and utensils after handling raw foods.

When to Call the Doctor

Call your doctor immediately if your child develops rapid or labored breathing, fever, poor feeding, vomiting, dehydration, a high-pitched cry, lethargy (excessive sleepiness), or irritability. If your child has listeriosis, the doctor can rule out any other illnesses and start treatment.

Reviewed by: Yamini Durani, MD
Date reviewed: October 2011
Originally reviewed by: Cecilia diPentima, MD