In the United States, about 1,100 persons become seriously ill with listeriosis each year. In New Jersey, about 20 cases are reported each year. One-third of all cases happen during pregnancy. A substantial proportion of the sporadic cases are also likely to be caused by food-borne transmission. Listeriosis can also be transmitted to a an unborn child during pregnancy or during childbirth.
Infected animals can also be a source of listeriosis.
Listeriosis can affect different body organs and thus cause a variety of symptoms. Usual symptoms include fever, muscle aches and sometimes nausea or diarrhea. Pregnant women with listeriosis may experience only mild flu-like illness. However, listeriosis during pregnancy often leads to premature delivery, infection of the newborn, or stillbirth. Symptoms generally occur about three weeks after coming into contact with Listeria monocytogenes, however it may be as short as 3 days or as long as 2 months.