Listeria is a common bacteria found in soil, water, and some animals, including cattle, according to the U.S. Health Department’s website: Foodsafety.gov. It can also be present in raw milk and foods made from raw milk.
Unlike many food pathogens, Listeria can grow in cold temperatures in the refrigerator. It is killed by cooking and pasteurization.
Common sources of Listeria include ready-to-eat deli meats, hot dogs, meat spreads, unpasteurized dairy products, and soft cheeses made with unpasteurized milk, such as queso fresco. In dairy products, Listeria contamination usually occurs after pasteurization, a problem called cross-contamination.
Listeria causes an uncommon, but potentially serious disease called listeriosis, marked by fever, severe headache, neck stiffness and nausea. Healthy people rarely contract listeriosis, according to the Minnesota Department of Agriculture, but it can sometimes cause fatal infections in infants, the elderly, and those with weakened immune systems. It can also lead to miscarriages in pregnant women.
In the spring of 2014, there were several recalls of dairy foods that may have been contaminated by Listeria, included two voluntary recalls by Coon Rapids, Minnesota-based Parkers Farm, Inc.