Listeria is a harmful bacterium that can cause a serious infection called listeriosis. Listeria can contaminate food through various pathways, potentially spreading during the production, processing, or packaging stages when proper sanitation measures are not in place.
More specifically, contamination typically occurs when food comes into contact with surfaces or equipment harboring Listeria monocytogenes, especially in facilities that handle raw or undercooked foods. Foods such as deli meats, unpasteurized dairy products, and pre-packaged salads are particularly vulnerable because they may not undergo further cooking, which would otherwise kill the bacteria. Additionally, improper storage or refrigeration can allow listeria to multiply, as it can grow even at low temperatures.