A listeria infection, or listeriosis, occurs when a person eats food contaminated with the bacterium listeria monocytogenes—especially foods like unpasteurized milk products and improperly processed meats. Although some people can get over a listeria infection without treatment, high-risk people can have complications, like meningitis, endocarditis, and encephalitis. High-risk people include women who are pregnant, people with weak immune systems, those with cancer, those with AIDS, alcoholics, diabetics, the elderly, and newborns.
In high-risk persons and those with comprised immune systems, the development of complications—like meningitis and septicemia—and more serious symptoms, like seizures, can occur. Pregnant women may feel flu-like symptoms, and in worse cases, can have a miscarriage, premature delivery, stillbirth, or infected newborn.
If a person has a mild case of listeriosis, then he or she does not need treatment and can let the infection run its course. However, high-risk persons should seek medical attention right away. For instance, pregnant women can often prevent an infection in the fetus if they have a doctor prescribe antibiotics. Newborns can also receive antibiotics for a listeria infection.