1. A group of bacteria that are capable of causing illness and possible fatal infections; especially, for elderly people, newborn-babies, pregnant women, and those with a weakened immune system: Symptoms of listeria include fever, muscle aches, nausea, and diarrhea.

If the infection of listeria spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur.

If listeria occurs during pregnancy, it may appear mild but it can lead to stillbirth, premature delivery, and infection of the newborn.

2. Etymology: named after the English surgeon and apostle of antisepsis, Joseph Lister (1827-1912).

A reference to a kind of bacteria which may be found in the feces of animals and humans, on vegetation, and in silage: The listeria species are parasitic on cold-blooded and warm-blooded animals, including people.

Listeria contamination has been responsible for numerous recalls of food.

Listeria infection may be spread through different methods including direct contact with infected lesions, food-borne transmission, and passage from mother to fetus in pregnancy or to the infant during birth.

Those who are at risk can prevent the listeria infection by avoiding certain high-risk foods and by handling food properly and so people should thoroughly cook raw food from animal sources; such as, beef, pork, or poultry; keep uncooked meats separate from vegetables, cooked foods and ready-to-eat foods; wash raw vegetables thoroughly before eating them, and avoid raw (unpasteurized) milk or foods made from raw milk.