Salmonella in Food: Sources, Symptoms, and How to Prevent It

Salmonella is responsible for more foodborne illness hospitalizations in the United States than any other bacteria. The CDC estimates 1.35 million infections per year, 26,500 hospitalizations, and 420 deaths. That’s not a rare problem hiding in obscure foods. Salmonella is in everyday grocery items — poultry, eggs, produce, nut butters — and it gets into kitchens constantly.

What matters is knowing where it lives, how it spreads, and what actually stops it.

What Salmonella Is

Salmonella is not a single bacteria species. It’s a genus containing over 2,500 different serovars — distinct strains that differ in their surface proteins. Two serovars cause most of the foodborne illness in the US: Salmonella Typhimurium and Salmonella Enteritidis.

All Salmonella serovars share a core mechanism. They colonize the intestinal tracts of animals — cattle, poultry, pigs, reptiles, some birds — without necessarily making those animals sick. Contamination of food happens when intestinal contents (fecal matter) come into contact with the food during slaughter, processing, or through irrigation water on crops.

The bacteria are hardy. They survive for extended periods on dry surfaces, can withstand mild acidity, and tolerate a wide range of temperatures. They don’t produce heat-stable toxins, which means thorough cooking destroys them reliably. Their danger is in the reproductive window before cooking — and in ready-to-eat foods that won’t be cooked at all.

Where Salmonella Hides in Your Food

Raw poultry is the primary vehicle. Chickens and turkeys are frequently colonized with Salmonella in their intestinal tracts, and contamination of the meat surface during processing is common. The USDA monitors Salmonella prevalence in poultry plants. Rates in raw chicken products vary by product type, but contamination is frequent enough that all raw poultry should be treated as potentially contaminated.

Eggs are a special case. Salmonella Enteritidis can infect a hen’s ovaries and be deposited inside the egg before the shell even forms. This is internal contamination — the bacteria is in the yolk or white, not on the shell. Washing the egg does nothing for this type of contamination. About 1 in 20,000 eggs carries internal Salmonella, which sounds low until you consider the scale of egg production and consumption. The FDA’s Egg Safety Rule requires producers to implement measures to prevent Salmonella Enteritidis in laying flocks and refrigerate eggs properly during transport and storage.

Raw ground beef carries risk because grinding distributes any surface contamination throughout the meat. A steak’s contamination is only on the surface, where heat from a pan or grill kills it quickly. Ground beef’s contamination is distributed through every bite, which is why the minimum safe temperature is 160°F throughout — not just at the surface.

Raw produce has been the source of multiple high-profile outbreaks. Salmonella contamination on produce typically comes from contaminated irrigation water, processing equipment, or animal manure used as fertilizer that wasn’t adequately composted. Sprouts are particularly high-risk because they’re grown in warm, humid conditions ideal for bacterial multiplication. Tomatoes, cantaloupe, and leafy greens have each been linked to outbreaks.

Unpasteurized dairy and juice carry risk because pasteurization is the kill step that neutralizes Salmonella and other pathogens. Without it, any Salmonella present in the raw material survives into the final product. Raw milk covers this in detail.

Nut butters might seem like a dry, stable product, but Salmonella can survive at low water activity. Several large peanut butter recalls have been linked to Salmonella contamination at processing facilities.

The Fecal-Oral Route

Every Salmonella contamination follows the same basic path: the bacteria lives in an animal’s intestines, gets out through feces, and finds a way into a food or onto a surface a human will touch.

In slaughterhouses, intestinal contents can contaminate meat during evisceration if the gut is nicked. In produce fields, contaminated water from streams near cattle operations soaks into the soil or sprays onto crops. In kitchens, a cutting board used for raw chicken and then for salad greens transfers bacteria directly. A hand that handled raw poultry and then reached into a bag of chips does the same.

This path explains why handwashing is so effective. Breaking the chain of transfer from contaminated food or surface to mouth interrupts the infection route.

Symptoms and Who’s Most at Risk

Salmonella symptoms follow a predictable pattern after that 6 hours to 6 day incubation period.

• Diarrhea (often watery, sometimes bloody)
• Fever, typically 100-102°F
• Stomach cramps and nausea

Most healthy adults recover in 4-7 days without treatment. The illness is unpleasant but self-limiting.

For vulnerable groups, the picture changes. In young children, the elderly, pregnant women, and immunocompromised individuals, Salmonella can spread beyond the gut. Bacteremia — Salmonella entering the bloodstream — occurs in about 5% of all cases. In high-risk groups, it’s more common and more severe. Bacteremia can lead to infections in other organs, including the bones, joints, urinary tract, and central nervous system.

Prevention: What Actually Works

Temperature is the primary defense. Salmonella is killed by heat through protein denaturation — the same process that cooks the food. At 165°F (74°C), Salmonella is destroyed essentially instantly. The USDA sets 165°F as the minimum for poultry because Salmonella is the primary pathogen of concern. Eggs should be cooked until both the yolk and white are firm. Ground beef should reach 160°F throughout.

A thermometer is the only reliable way to confirm these temperatures. Color is not. Chicken can look white and cooked at temperatures below 165°F. A thermometer removes the guesswork.

Don’t wash raw chicken. It seems counterintuitive, but rinsing spreads Salmonella rather than removing it. Water hitting raw chicken creates a fine mist that carries bacteria to nearby surfaces — the sink, the counter, nearby utensils. Studies have shown contamination spreading up to 3 feet from the rinse point. The washing raw chicken article covers the research. Cooking to 165°F kills Salmonella on the chicken. Washing doesn’t.

Refrigerate promptly. Salmonella multiplies in the temperature danger zone (40-140°F). Food left at room temperature for more than 2 hours allows bacterial populations to grow toward infectious levels. The 2-hour rule applies to raw food waiting to be cooked and to cooked food waiting to be stored.

Prevent cross-contamination. Raw poultry and eggs should be handled on separate surfaces from ready-to-eat food. Wash hands with soap for 20 seconds after handling raw poultry, eggs, or any raw protein. Don’t reuse marinades that touched raw meat unless you boil them first. See cross-contamination for a full breakdown.

The Cross-Contamination Connection

One of the most common ways Salmonella causes illness isn’t through undercooked poultry — it’s through cross-contamination to foods that are eaten raw. Juice from a package of raw chicken dripping onto strawberries. A knife that cut raw chicken transferred to cut tomatoes without washing in between. These are the scenarios that cause illness even in households where nobody eats undercooked meat.

The cross-contamination article covers the specific transfer routes and prevention strategies. The key pattern: anything that touches raw poultry, eggs, or beef needs to be washed before it touches ready-to-eat food.

Proper cooking through heat — specifically, reaching the temperatures in the safe internal temperatures guide — kills Salmonella reliably. The biology is not complicated. The temperature that denatures food proteins also denatures bacterial proteins. The food is done when the bacteria are dead.