Listeria monocytogenes has been recognized as a human pathogen for 60 years, but food was not thought to be a vehicle of transmission until recently. In the United States, an estimated 2,000 persons become seriously ill with listeriosis each year. Of these, 500 die. Pregnant women, newborns, and adults with weakened immune systems are primarily at risk. About one-third of Listeria monocytogenes cases occur during pregnancy.
Listeria monocytogenes is found in soil and water. Vegetables can become contaminated from the soil or from manure used as fertilizer. Animals can carry the bacteria without appearing ill and can contaminate foods of animal origin such as meats and dairy products. The bacteria can be found in a variety of raw foods, such as uncooked meats and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheeses and cold cuts at the deli counter. Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacteria.
Symptoms vary and depend on the individual's susceptibility, but may include fever, fatigue, nausea, vomiting and diarrhea.
More Information on Listeria monocytogenes:
Listeriosis Information - Centers for Disease Control