Listeria monocytogenes is a type of bacteria that can cause a serious infection known as listeriosis. It is commonly found in contaminated food, particularly in unpasteurized dairy products, deli meats, and raw vegetables. The bacteria can survive and grow in cold temperatures, making it a concern for food safety. People at higher risk for listeriosis include pregnant women, newborns, the elderly, and individuals with weakened immune systems. Symptoms may include fever, muscle aches, and gastrointestinal issues. In severe cases, it can lead to complications such as meningitis or septicemia, highlighting the importance of proper food handling and hygiene.