Past Its Prime: How Leftovers and Expired Foods Can Harbor Listeria

We’ve all done it—opened the fridge, taken a sniff of last week’s takeout, shrugged, and microwaved it anyway. But while leftovers and refrigerated foods may look and smell fine, some can quietly become dangerous over time. One of the stealthiest threats lurking in your fridge is Listeria monocytogenes, a bacteria that thrives in cold, moist environments and causes the serious illness listeriosis.

Unlike many other foodborne pathogens that die off in the cold, Listeria actually flourishes in refrigeration. That means the foods we trust to stay safe—deli meats, soft cheeses, packaged salads—may be among the riskiest when mishandled or forgotten too long.

What Makes Listeria So Unique?

Listeria monocytogenes is particularly dangerous because:

And while healthy individuals may recover fro