Listeria can show up in a surprisingly wide range of foods, from deli meats and soft cheeses to fresh melons and frozen vegetables. Unlike most foodborne bacteria, Listeria monocytogenes grows at refrigerator temperatures, which means foods you assume are safely stored in your fridge can still harbor dangerous levels of contamination. Here’s what to watch for across every major food category.
Deli Meats and Ready-to-Eat Meat Products
Deli meats are one of the most common sources of listeria outbreaks. Sliced turkey, ham, roast beef, salami, and other cold cuts can become contaminated during processing at the facility or at the deli counter itself. The CDC has linked multiple recent outbreaks specifically to meats sliced at delis, not just prepackaged products. Because these meats are eaten cold, the bacteria never gets killed by cooking.
Hot dogs carry the same risk when eaten without reheating. Pâté and meat spreads are also susceptible because they’re processed in environments where listeria can persist on equipment surfaces. If you’re pregnant, over 65, or have a weakened immune system, the CDC recommends either avoiding deli meat entirely or reheating it to an internal temperature of 165°F (steaming hot) before eating.
Soft Cheeses and Unpasteurized Dairy
Certain soft cheeses are made in ways that allow listeria to contaminate the product and continue growing. Queso fresco is especially high-risk and has been linked to repeated outbreaks, along with cotija cheese. Brie and Camembert have also caused outbreaks. The soft, moist texture and relatively low acidity of these cheeses create a hospitable environment for the bacteria.
Any dairy product made from unpasteurized (raw) milk carries elevated risk. That includes raw milk itself, plus raw-milk yogurt, ice cream, and cheese. Pasteurization heats milk to a temperature high enough to kill listeria and other harmful bacteria. Choosing pasteurized dairy products is one of the simplest ways to reduce your exposure.
Sprouts and Melons
Among fruits and vegetables, sprouts and melons stand out as the highest-risk categories. Sprouts (alfalfa, mung bean, clover) need warm, humid growing conditions that are also ideal for listeria. The bacteria can grow on both the inside and outside of sprouts, so washing alone doesn’t make them safe.
Melons, particularly cantaloupe, are more likely than most other fruits to carry listeria. Two characteristics make them vulnerable: they have low acidity, and people tend to store cut melon in the refrigerator for several days. Since listeria thrives in cold environments, that extended storage time gives the bacteria a chance to multiply. Pre-cut melon from a store or salad bar adds another handling step where contamination can occur.
Other produce linked to outbreaks includes leafy greens, peaches, nectarines, plums, and celery. Fresh produce can pick up listeria from contaminated soil, water, or processing equipment.
Cold-Smoked Fish and Seafood
Refrigerated smoked seafood is a well-established source of listeria. Cold-smoked fish, often labeled as “nova-style,” “lox,” “kippered,” or “smoked,” is processed at temperatures too low to kill the bacteria. If the processing facility has listeria present on its equipment, the finished product can be contaminated from the start.
Refrigeration won’t save you here. Listeria survives and multiplies at fridge temperatures, so contaminated smoked salmon or trout only becomes more dangerous the longer it sits. Safer alternatives include shelf-stable smoked fish (the kind sold in sealed pouches or cans that don’t require refrigeration until opened) or smoked fish that’s been fully cooked.
Frozen Fruits and Vegetables
Freezing does not kill listeria. Research tracking the bacteria on individually quick-frozen vegetables stored at standard freezer temperatures found that listeria populations remained essentially stable for an entire year, declining by less than half a log unit over 360 days. Two recent outbreaks in the U.S. and Europe were traced to contaminated frozen vegetables, including frozen corn.
Some frozen vegetable packages include cooking instructions and are not intended to be eaten raw, but consumers often add them directly to salads or smoothies. If your frozen fruits or vegetables are labeled with cooking instructions, following those instructions is the safest approach.
Why Listeria Behaves Differently
Most bacteria slow down or stop growing in a refrigerator set to 40°F (4°C) or below. Listeria is unusual because it can grow at temperatures as low as just below freezing. Lab studies have documented growth at temperatures between -0.4°C and 9.3°C, with the bacteria doubling roughly every 13 to 24 hours at typical fridge temperature (5°C). This means a food with a small amount of contamination on the day you buy it can have significantly higher bacterial levels a week later.
This cold-growth ability is what makes ready-to-eat refrigerated foods so risky. Anything that gets eaten without further cooking, and sits in your fridge for days, gives listeria time to reach dangerous levels.
Who Faces the Greatest Risk
Listeria infection hits certain groups far harder than others. Pregnant women are roughly 10 times more likely to get listeriosis because pregnancy alters the immune system in ways that make it harder to fight off infection. A pregnant person might experience only mild, flu-like symptoms or feel nothing at all, while the infection causes miscarriage, stillbirth, premature delivery, or life-threatening illness in the newborn, including blood infections and meningitis.
Adults over 65 and people with weakened immune systems (from cancer treatment, organ transplants, diabetes, liver or kidney disease, or HIV) are also at high risk. Invasive listeriosis, the severe form where the bacteria enters the bloodstream or brain, has a fatality rate of 20 to 30 percent. For otherwise healthy adults, listeria typically causes a bout of gastroenteritis that starts about 24 hours after eating contaminated food and resolves on its own. The invasive form can take much longer to appear, with a median incubation period of 8 days and a range stretching from 1 to 67 days.
Reducing Your Risk at Home
Your refrigerator itself can be a source of cross-contamination. Listeria from a leaking deli meat package or dripping raw meat juices can colonize shelves and drawers, then spread to other foods. Clean spills immediately and periodically wipe down the inside walls and shelves with hot water and mild dish soap, then rinse and dry with a clean cloth.
Beyond fridge hygiene, a few practical habits make a real difference:
- Eat perishable foods quickly. The longer ready-to-eat items sit in your fridge, the more time listeria has to grow. Use opened deli meats and smoked fish within three to five days.
- Keep raw and ready-to-eat foods separated. Store raw meat on the lowest shelf to prevent juices from dripping onto produce, cheeses, or leftovers.
- Choose pasteurized dairy. Check labels on soft cheeses, especially those from farmers’ markets or imported from countries with less regulated dairy production.
- Heat deli meats if you’re in a high-risk group. Bringing cold cuts to 165°F kills listeria effectively.
- Cook frozen vegetables if the package says to. Don’t assume all frozen produce is ready to eat straight from the bag.