Listeria monocytogenes is a germ that can grow in cold temperatures, including in refrigerators. CDC notes it is often linked to unpasteurized dairy, soft cheeses, deli meats, and other ready-to-eat foods.
Listeriosis can be serious. CDC says pregnant people, newborns, adults 65 and older, and people with weakened immune systems are at higher risk.
Follow CDC and FoodSafety.gov guidance on safe food handling and which foods higher-risk groups should avoid.