Listeria is most commonly found in deli meats, soft cheeses, smoked seafood, raw milk, and certain produce like melons and sprouts. What makes this bacterium unusual is that it thrives in cold temperatures, meaning refrigeration does not stop it from growing. Most foodborne bacteria go dormant in your fridge, but Listeria multiplies at temperatures as low as 31°F.
Deli Meats, Hot Dogs, and Cold Cuts
Ready-to-eat meats are one of the most frequent sources of Listeria contamination. Deli meats, cold cuts, hot dogs, and fermented or dry sausages all carry risk. The issue is not that these meats were improperly cooked. They are typically cooked or processed before packaging, but they can pick up Listeria afterward by touching contaminated surfaces, equipment, or hands in the production facility or at the deli counter.
Products sliced or prepared at a deli counter are particularly risky because Listeria spreads easily among shared slicers, countertops, and utensils. If you’re in a high-risk group, heating deli meats until they’re steaming hot (165°F internally) kills the bacteria. Eating them straight from the package, at refrigerator temperature, does not.
Soft Cheeses and Raw Milk
Soft cheeses are more likely to harbor Listeria than hard cheeses because of their high moisture content, which creates a better environment for the bacteria to grow. Queso fresco, Brie, and cotija are among the varieties linked to outbreaks. Queso fresco-type cheeses are especially problematic: they’re fresh, soft, high in moisture, low in acidity, and they skip the extended aging process that helps kill Listeria in harder cheeses. The CDC has documented repeated multistate outbreaks tied to queso fresco, including as recently as 2024.
Raw (unpasteurized) milk and anything made from it, including cheese, yogurt, and ice cream, can also carry Listeria. Pasteurization kills the bacteria, so choosing pasteurized dairy products eliminates much of the risk. Check labels carefully, especially at farmers markets or specialty shops where raw milk products are more common.
Smoked and Refrigerated Seafood
Cold-smoked fish is a significant Listeria risk because the cold-smoking process does not reach temperatures high enough to kill the bacteria. Products labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky” that require refrigeration fall into this category. If Listeria is present in the facility where the fish was processed, it can survive on the product through packaging, shipping, and storage in your fridge.
Safer alternatives are shelf-stable smoked fish products, which are heat-treated and sealed in airtight containers that don’t need refrigeration before opening. Cooking smoked fish thoroughly before eating also kills any Listeria present.
Melons and Sprouts
Among fruits and vegetables, melons and sprouts stand out as higher-risk foods. Cantaloupes were the source of one of the deadliest Listeria outbreaks in U.S. history in 2011. Melons are vulnerable because they have low acidity and people often store cut pieces in the refrigerator for days, giving the bacteria time to multiply.
Sprouts, including alfalfa, mung bean, and clover varieties, need warm, humid conditions to grow. Those same conditions are ideal for Listeria and other harmful bacteria. The germs can grow both inside and on the surface of sprouts, so washing them does not make them safe. Even home-grown sprouts carry the same risk because they require the same growing environment. A 2015 multistate outbreak was linked directly to sprouts.
Why Listeria Survives Where Other Bacteria Don’t
Listeria is unusually tough. It grows in refrigerators at 38°F to 40°F and accelerates above 40°F. It tolerates a wide range of acidity (pH 4.0 to 9.6) and can survive in salt concentrations up to 13 to 14 percent. For comparison, most cured meats contain around 2 to 3 percent salt, well within Listeria’s comfort zone. The bacteria actually survive better in salty environments at lower temperatures, which means salt-cured, refrigerated foods offer less protection than you might assume.
This resilience is why Listeria is so persistent in food processing facilities. It colonizes equipment, drains, and surfaces, then recontaminates foods that were already cooked or processed. The longer a ready-to-eat food sits in your refrigerator, the more time Listeria has to multiply to dangerous levels.
Who Faces the Greatest Risk
Listeria infection is rare in the general population, with roughly 800 cases reported annually in the United States. But when infection does occur, it is severe: 91% of non-pregnancy-related cases result in hospitalization, and about 18% are fatal.
Four groups face the highest risk: pregnant women, newborns, adults 65 and older, and people with weakened immune systems. About 1 in 25,000 pregnant women in the U.S. develop a Listeria infection each year. The consequences can be devastating. One in four pregnant women with listeriosis lose their pregnancy or their baby shortly after birth. The infection can pass to the baby even when the mother’s symptoms are mild.
Older adults are more vulnerable because the immune system becomes less effective at identifying and clearing harmful bacteria with age. Stomach acid, which helps kill ingested pathogens, also decreases over time. People on immunosuppressive medications, those with HIV, cancer patients undergoing treatment, and organ transplant recipients are the group most likely to develop severe infection.
Reducing Your Risk at Home
Keep your refrigerator at 40°F or below and use a thermometer to verify, since built-in dials are often inaccurate. Eat perishable and ready-to-eat foods promptly rather than storing them for extended periods. The longer deli meats, cut melons, or soft cheeses sit in your fridge, the more opportunity Listeria has to grow.
Prevent cross-contamination by keeping raw meat, poultry, and seafood wrapped securely and separated from ready-to-eat foods. Use separate cutting boards, and wash your hands thoroughly after handling raw meat or its packaging. When thawing frozen meat in the refrigerator, place it in a bag or dish to catch any dripping juices. Clean deli meat juice or any spills from refrigerator shelves promptly, since Listeria can persist on surfaces and spread to other foods stored nearby.
For anyone in a high-risk group, the most effective strategy is avoiding the highest-risk foods altogether: skip deli counter meats unless reheated, choose hard cheeses or pasteurized soft cheeses, avoid raw sprouts, eat cut melon promptly, and opt for shelf-stable or cooked smoked fish over cold-smoked varieties.