Listeria infection, also known as Listeriosis, is an infection caused by the bacteria listeria. Listeriosis is spread through contaminated food by the Listeria bacteria, direct contact with infected animals, or mother to child transmission during pregnancy. Listeria bacteria can be found in contaminated food through soil or manure used as fertilizer, uncooked meats and vegetables, processed foods that have become contaminated during or after processing, and unpasteurized milk or foods. People with a higher risk of serious illness from listeria include pregnant women, unborn babies and newborns, people with weakened immune systems, and older adults. Symptoms of listeriosis include fever, muscle aches, nausea, or diarrhea, with most people only having mild symptoms. Other symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can appear if the infection spreads to the nervous system. Listeriosis can be treated with antibiotics and can be prevented by thoroughly cooking all raw foods, washing fruits and vegetables, and avoiding unpasteurized milk or foods.