You get Salmonella by swallowing the bacteria, usually through contaminated food, contact with animals, or exposure to contaminated water. In the United States, Salmonella causes roughly 1.28 million illnesses every year and is the leading cause of death among foodborne pathogens, killing an estimated 238 people annually. Most people pick up the infection without realizing exactly when it happened, because the bacteria can hide in foods and environments that seem perfectly clean.
Contaminated Food Is the Most Common Source
The majority of Salmonella infections come from eating contaminated food. The bacteria live in the intestines of animals raised for food, and they can end up on or inside products at any stage from farm to table.
Poultry and eggs top the list. Chickens and turkeys frequently carry Salmonella in their digestive tracts, and the bacteria transfer easily to raw meat during processing. With eggs, contamination can happen on the outside of the shell, but it can also start before the shell even forms. Salmonella can colonize a hen’s ovarian tissue and infect the yolk or surrounding membrane while the egg is still developing inside the bird. That means even an intact, clean-looking egg can contain bacteria on the inside.
Raw or undercooked beef, pork, and seafood also carry risk. Salmonella can survive in frozen meat for a year or more, so freezing alone does not kill it. The bacteria can also grow at temperatures as low as 36°F, which is right around standard refrigerator temperature. Only thorough cooking reliably destroys them.
Less obvious sources catch people off guard. Fresh produce like leafy greens, tomatoes, and melons can pick up Salmonella from contaminated irrigation water, soil, or handling during harvest. Raw flour is another overlooked carrier: grain can be contaminated in the field and the bacteria survive in the dry, low-moisture environment for months or even years. Nut butters and similar shelf-stable products have caused outbreaks for the same reason. Salmonella is unusually tough and can persist at very low moisture levels, which is why dry pantry items aren’t automatically safe.
One particularly sneaky risk involves frozen products that look pre-cooked but aren’t. Breaded, browned chicken products like frozen chicken cordon bleu or chicken kiev have caused Salmonella outbreaks because consumers assumed they were ready to eat when they were actually raw inside.
Cross-Contamination in the Kitchen
You don’t have to eat the contaminated food itself to get sick. If raw chicken juice drips onto a countertop where you later chop vegetables, or you use the same cutting board for raw meat and then for salad without washing it, the bacteria transfer to foods that won’t be cooked. This is cross-contamination, and it’s one of the most common ways Salmonella infections happen at home.
The key mistakes are using the same utensils or cutting boards for raw and cooked foods, not washing hands after handling raw meat or eggs, and letting raw juices contact surfaces where ready-to-eat food is prepared. Salmonella doesn’t need visible mess to spread. A thin film of moisture from raw poultry is more than enough.
Reptiles, Backyard Chickens, and Other Animals
Touching animals is the second major route of infection, and it catches many people by surprise. Reptiles and amphibians are especially likely carriers. Snakes, iguanas, turtles, frogs, and toads commonly carry Salmonella in their digestive tracts and shed it in their droppings. The bacteria end up on their skin, on the surfaces of their enclosures, and on anything in their habitat: bedding, rocks, food dishes, and water bowls.
You don’t need to touch the animal’s droppings directly. Simply handling a reptile, cleaning its tank, or touching objects from its enclosure can transfer Salmonella to your hands. From there, touching your mouth, eating, drinking, or smoking before washing your hands completes the chain. The FDA specifically warns against kissing pet reptiles or amphibians, bathing them in kitchen or bathroom sinks, or letting them roam freely through areas where food is prepared or eaten.
Backyard chickens and ducks pose similar risks. Their feathers, feet, and coop surfaces can all harbor the bacteria. Even chicks and ducklings that look healthy carry Salmonella. Children under 5, older adults, pregnant women, and anyone with a weakened immune system face the highest risk from animal contact and ideally should avoid handling these animals altogether.
Feeder rodents, the frozen or live mice and rats sold as food for pet snakes, are another source. Thawing them in a microwave you use for your own food or preparing them with kitchen utensils creates a direct path for the bacteria to reach you.
Raw Pet Food
Feeding your dog or cat a raw diet introduces Salmonella risk for the humans in the household, not just the pet. The raw meat in these diets can carry the bacteria, and you can pick it up while scooping food, handling the bowl, or touching surfaces the food contacted. Your pet can also spread the bacteria by licking your face after eating. The FDA recommends treating raw pet food with the same caution you’d use for raw meat you’re preparing for yourself: wash hands thoroughly afterward and keep contaminated surfaces away from human food.
Contaminated Water
Salmonella can contaminate drinking water, recreational water, and irrigation water. Drinking untreated water from streams, ponds, or lakes while swimming or camping is a recognized risk. Municipal water supplies are generally treated to kill bacteria, but private wells and surface water sources don’t have the same protections.
When contaminated water is used to irrigate crops or rinse produce before or after harvest, the bacteria transfer to fruits and vegetables. This is one reason produce-linked Salmonella outbreaks occur even when the food was grown in seemingly clean conditions.
Person-to-Person Spread
Salmonella spreads from person to person through what’s called the fecal-oral route. If someone with an active infection doesn’t wash their hands thoroughly after using the bathroom, they can transfer bacteria to surfaces, shared objects, or food they prepare for others. This is most common in households with young children in diapers and in group settings like daycare centers or nursing homes.
How Many Bacteria It Takes
The number of Salmonella bacteria needed to make you sick varies widely, from as few as 1,000 organisms to as many as 10 billion. That enormous range depends on the specific strain, the type of food carrying it (high-fat foods like peanut butter may protect bacteria from stomach acid), and your individual vulnerability. People with weakened immune systems, young children, and older adults can get sick from much smaller doses. In a healthy adult, the median dose that causes illness for common strains is estimated at around 125 million bacteria, but certain strains can infect with just a few thousand.
How Quickly Symptoms Appear
Symptoms typically start 6 hours to 6 days after you swallow the bacteria. Most people develop diarrhea, fever, and stomach cramps that last 4 to 7 days. Diarrhea can persist for up to 10 days in some cases, and it may take several months for your bowel habits to fully return to normal. The wide incubation window is part of why it’s hard to pin down exactly which food or exposure was responsible. By the time you feel sick, you may have eaten dozens of meals since the one that infected you.