Listeria monocytogenes is a type of bacteria that lives in soil and water and causes the infection listeriosis by means of contaminated food, according to the Centers for Disease Control and Prevention. People with weakened immune systems, the elderly, expectant women and newborns are most vulnerable to the infection.
Listeria infects humans through foods such as uncooked meat, raw vegetables, unpasteurized milk products and some processed foods, explains the CDC. Those affected have symptoms that include diarrhea, fatigue, muscle aches, fever and loss of balance. However, expectant women infected with listeriosis risk miscarrying or having a premature delivery or stillborn birth. Pasteurizing and cooking are processes that kill listeria.