The seemingly long shelf life for the Listeria in these products results, in part, from how the foods are stored: in the freezer. [5 Scariest Disease Outbreaks of the Past Century] Listeria can live for a really long time in the freezer, said Benjamin Chapman, a food-safety specialist and an associate professor at North Carolina State University. In fact, freezing is how scientists preserve bacteria when they want to study the organisms in the lab, Chapman told Live Science. Although freezing temperatures will prevent Listeria bacteria from growing, they don’t kill the bacteria, Chapman said. The microbes survive in the freezer, he said.
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