Listeriosis: A disease that is caused by eating food contaminated with the bacterium Listeria monocytogenes. Listeriosis is an important public health problem in North America. The disease affects primarily pregnant women, newborns, and anyone who is immunocompromised. Symptoms include fever, muscle aches, nausea, and diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur. Infection during pregnancy may appear mild but can lead to stillbirth, premature delivery, and infection of the newborn. Persons who are at risk of contracting Listeriosis can prevent the infection by avoiding certain high-risk foods and by handling food properly. Raw food from animal sources (such as beef, pork, or poultry) should be thoroughly cooked and uncooked meats should be kept separate from vegetables, cooked foods, and ready-to-eat foods. Raw vegetables should be washed thoroughly before being eaten, and raw (unpasteurized) milk or foods made from raw milk should be avoided.