Listeria bacteria primarily come from contaminated raw meats, unpasteurized dairy, and ready-to-eat foods. These foods often harbor the pathogen due to improper handling or processing.
Listeria monocytogenes thrives in moist environments and can grow at refrigeration temperatures. It enters food through contact with contaminated soil, water, or equipment during farming, processing, or storage. Unlike most bacteria, listeria can survive and even multiply in cold temperatures, making refrigeration less effective at preventing growth.
The following foods are most likely to carry listeria:
According to the CDC, listeria causes about 1,600 illnesses and 260 deaths annually in the U.S., with pregnant women, newborns, older adults, and immunocompromised individuals at highest risk.
Many assume only raw foods carry listeria, but ready-to-eat processed foods often pose higher risks because they may be contaminated after cooking. For example, deli meats sliced at grocery stores can introduce listeria if slicers aren't properly cleaned between uses.
Another myth is that cooking kills listeria. While heat treatment eliminates the bacteria, cross-contamination during food preparation can reintroduce it. A 2018 study in the Journal of Food Protection found that 2.1% of retail deli meats tested positive for listeria, highlighting ongoing risks even in cooked products.
To minimize exposure, follow these steps:
When I prepared my Thanksgiving turkey last year, I kept the raw bird and its juices away from cooked foods and washed my hands frequently. This practice prevents cross-contamination that could lead to listeria exposure.