Name one common source of listeria.

Unpasteurized dairy products are a well-known source of Listeria monocytogenes, the bacteria responsible for listeriosis. This bacterium can thrive in the environment, particularly in foods that are raw or unprocessed. Unpasteurized dairy products, such as certain types of cheese and milk, have not been heat-treated to kill pathogens, which includes Listeria. As a result, consuming these unpasteurized items significantly increases the risk of listeriosis, especially in vulnerable populations such as pregnant women, the elderly, and individuals with weakened immune systems.

Canned vegetables, cooked meats, and frozen fruits present a much lower risk for Listeria because the processing methods (such as canning and cooking) generally eliminate or reduce harmful bacteria. While it's still important to handle and store all food safely, unpasteurized dairy remains a critical point of concern in listeria-related food safety.