Salmonella reaches people through contaminated food, direct contact with animals, exposure to contaminated water, and occasionally from other infected people. Contaminated poultry, eggs, and raw meat are the most familiar sources, but the list of routes is longer and stranger than most people expect. Fruits, vegetables, spices, pet food, pet reptiles, and even your own kitchen sponge can deliver a dose of the bacterium large enough to make you sick.
Poultry, Eggs, and Raw Meat
If you picture one food when you hear “Salmonella,” it is probably chicken, and for good reason. Poultry is one of the most common vehicles for the bacterium. Salmonella lives in the intestines of chickens and other birds, and during slaughter and processing it can transfer to the meat. The bacteria also form resilient communities called biofilms on equipment surfaces in poultry processing plants, which helps explain why contamination persists even in facilities with cleaning protocols.1PubMed Central. Biofilm formation in food processing plants and novel control strategies to combat resistant biofilms: the case of Salmonella spp.
Eggs are a particularly interesting case. One specific strain, Salmonella Enteritidis, has a unique ability to colonize the reproductive tissues of laying hens, which means the bacterium can end up inside the egg before the shell even forms. Other strains tend to contaminate only the eggshell surface.2PubMed. Salmonella in eggs and egg-laying chickens: pathways to effective control This is why even eggs with clean, uncracked shells can harbor the bacteria internally, and why cooking eggs thoroughly matters more than just washing them.
Raw or undercooked beef and pork carry risk too. When ground pork sits at room temperature or in a poorly refrigerated environment, Salmonella can multiply rapidly. Researchers modeling temperature abuse in raw ground pork found that even moderate warmth between 10 and 40°C allowed meaningful bacterial growth.3PubMed. Modeling the growth of Salmonella in raw ground pork under dynamic conditions of temperature abuse The practical lesson: leaving raw meat on the counter while you prep other ingredients creates a window for the bacteria to multiply well beyond safe levels.
Fresh Fruits and Vegetables
Salmonella on produce catches people off guard. You expect risk from raw chicken; you don’t expect it from a bag of lettuce or a melon. But produce-associated outbreaks are surprisingly common. From 2006 to 2017, roughly a third of foodborne Salmonella outbreaks in the United States were linked to produce consumption.4PubMed Central. Presence and Persistence of Salmonella in Water: The Impact on Microbial Quality of Water and Food Safety
The contamination usually starts in the field, not at the grocery store. Irrigation water drawn from rivers, lakes, or ponds can carry Salmonella, and once that water contacts crops, the bacteria can persist on the plant and in the surrounding soil for extended periods. Research has shown that both contaminated irrigation water and contaminated manure compost can introduce Salmonella to soil and vegetables, and that the pathogen survives for a long time regardless of which route brought it there.5PubMed. Persistence of Salmonella enterica serovar typhimurium on lettuce and parsley and in soils on which they were grown in fields treated with contaminated manure composts or irrigation water Though actual uptake of Salmonella into the internal tissues of plants like lettuce appears to be relatively uncommon, the bacteria sit on outer surfaces where a rinse under the tap won’t necessarily remove them.6PubMed. Concomitant uptake of antimicrobials and Salmonella in soil and into lettuce following wastewater irrigation
Surface water quality is a key variable. Groundwater generally offers better microbial quality for irrigation, while rivers, lakes, and ponds are more likely to contain Salmonella. The bacteria can survive in aquatic environments for long periods by entering a dormant-but-alive state or by sheltering inside tiny single-celled organisms called protozoa that live freely in the water.4PubMed Central. Presence and Persistence of Salmonella in Water: The Impact on Microbial Quality of Water and Food Safety
Foods You Would Not Suspect
Some of the most puzzling Salmonella outbreaks in recent decades have involved dry, shelf-stable foods that seem like they should be too hostile an environment for bacteria: peanut butter, flour, dried spices, and sesame seeds. Salmonella does not grow in these foods the way it does in moist chicken or eggs, but it can survive in them for months or even years.
The reason is that low moisture actually protects the bacteria from heat. In wetter foods, heat kills Salmonella relatively quickly. In dry or fatty foods like peanut butter, the bacteria become far more heat-resistant. Researchers testing Salmonella survival during cookie baking found that the low starting moisture of peanut butter dough gave the bacteria greater heat resistance than what would be expected in a wetter food.7Journal of Food Protection. Survival of Salmonella during Baking of Peanut Butter Cookies In separate experiments comparing wheat flour and peanut butter at the same temperature, Salmonella survived roughly two and a half times longer in peanut butter, partly because the moisture level in peanut butter actually drops further as it heats up, giving the bacteria even more protection.8Food Research International. Water activity change at elevated temperatures and thermal resistance of Salmonella in all purpose wheat flour and peanut butter
Black pepper is another surprisingly common vehicle. Testing at farms and processing plants found Salmonella in soil, drying waste, dried peppercorns, and even finished export products, and the contamination that occurred after harvest was not eliminated during processing.9PubMed. Salmonella in black pepper (Piper nigrum): From farm to processing Sesame seeds have also tested positive in market surveys, with multiple Salmonella strains identified in imported samples.10PubMed Central. Assessment of contamination of Salmonella spp. in imported black pepper and sesame seed and salmonella inactivation by gamma irradiation Because spices and seeds are often added to dishes after cooking or sprinkled on top of finished food, any Salmonella present never gets a heat treatment.
Reptiles, Backyard Chickens, and Other Live Animals
You do not have to eat anything to get Salmonella. Simply handling an animal that carries the bacteria and then touching your mouth or food can be enough. Reptiles are the most well-known animal reservoir outside of poultry. A review of detection studies found Salmonella in more than half of snakes tested, about a third of lizards and tortoises, and a smaller fraction of turtles and crocodilians.11PubMed Central. Salmonella in reptiles: a review of occurrence, interactions, shedding and risk factors for human infections Captive reptiles shed the bacteria at substantially higher rates than wild ones. A large meta-analysis estimated Salmonella prevalence at about 38% in captive reptiles compared to about 15% in the wild.12PubMed Central. Salmonella prevalence and serovar distribution in reptiles: a systematic review and meta-analysis The stress of captivity, close quarters, and indoor housing all seem to play a role.
Backyard poultry flocks are another growing source of human infections. Between 1990 and 2014, over 50 outbreaks of Salmonella linked to live poultry were documented in the United States, involving more than 2,600 illnesses, nearly 400 hospitalizations, and five deaths.13PubMed Central. Outbreaks of Human Salmonella Infections Associated with Live Poultry, United States, 1990-2014 Chicks and ducklings were the most common sources of exposure. Among infected people, nearly half had kept the birds inside their homes, and about one in eight reported kissing birds. These outbreaks have risen alongside the popularity of keeping backyard flocks.14PubMed Central. Backyard poultry flocks and salmonellosis: a recurring, yet preventable public health challenge
Dogs and cats can also be carriers, especially if they eat raw diets. Surveys across Europe and North America have consistently found Salmonella in a proportion of commercially sold raw pet food.15PubMed Central. Raw diets for dogs and cats: a review, with particular reference to microbiological hazards A large internet-based survey of raw-feeding households found that self-reported transmission of any pathogen from raw pet food to a human family member was rare, occurring in a fraction of a percent of households, but the authors noted the limitations of self-reporting for detecting something like mild food poisoning that people may not link to pet food.16PubMed Central. Owners’ perception of acquiring infections through raw pet food: a comprehensive internet-based survey The risk is probably highest for young children, elderly household members, and anyone with a weakened immune system who comes into contact with the pet’s food bowl, feces, or saliva.
Cross-Contamination in Your Kitchen
A major share of Salmonella infections do not come from eating the contaminated food itself but from bacteria that spread to other surfaces and foods during preparation. The classic scenario involves cutting raw chicken on a board and then using the same board, knife, or unwashed hands to prepare a salad. Research modeling this pathway found that cross-contamination from raw chicken carcasses to kitchen surfaces and then onto ready-to-eat foods like salad is a meaningful contributor to foodborne illness in homes.17Journal of Food Protection. A Quantitative Analysis of Cross-Contamination of Salmonella and Campylobacter spp. Via Domestic Kitchen Surfaces
One practice that gets people into trouble is washing raw chicken under the faucet before cooking. The intent is good, but the splashing sends bacteria-laden water droplets across the sink and surrounding countertop. Experiments using high-speed imaging confirmed that bacteria from chicken surfaces transfer through splash droplets, and that faucet height, flow type, and the soft, deformable surface of raw poultry all influence how far those droplets travel.18PubMed Central. Chickensplash! Exploring the health concerns of washing raw chicken Cooking the chicken kills the Salmonella on the meat itself; washing it just spreads bacteria around the kitchen before you cook.
Temperature management after purchase matters just as much. Chicken breast left at room temperature shows dramatic bacterial growth within hours. At 25°C, Salmonella counts in chicken increased by nearly five log units in 12 hours, while refrigeration at 5°C held growth to less than two log units over the same period.19Food Science and Technology. Bacterial growth in chicken breast fillet submitted to temperature abuse conditions The practical rule is straightforward: refrigerate raw meat and eggs promptly, keep the fridge below 4°C, and never let raw animal products sit at room temperature longer than you absolutely must.
Who Is Most Vulnerable
Most healthy adults who swallow Salmonella experience a few miserable days of diarrhea, fever, and cramps before recovering without treatment. But certain groups face much more serious outcomes, including bloodstream infections, hospitalization, and death.
Older adults bear a disproportionate burden. In Canada, seniors accounted for half of all hospitalizations and over 80% of deaths from nontyphoidal Salmonella in the adult population, and their hospital stays averaged nearly twice as long as those of younger adults.20PubMed Central. Hospitalizations associated with salmonellosis among seniors in Canada, 2000-2010 Data from England tell a similar story: adults over 65 were more than three times as likely to develop Salmonella in the bloodstream compared to younger adults, and among those who did develop bloodstream infections, the vast majority of deaths were in people 65 and older.21PubMed Central. Epidemiology and Outcomes of Nontyphoidal Salmonella Bacteremias from England, 2004 to 2015 Newborns were also at elevated risk for bloodstream infection.
People taking proton pump inhibitors (PPIs), a widely used class of acid-suppressing medications, appear significantly more likely to develop Salmonella infections. Stomach acid is one of your body’s first defenses against swallowed bacteria, and PPIs reduce that acid. A large case-control study found that people currently taking PPIs had roughly five times the odds of developing nontyphoidal Salmonella compared to non-users.22PubMed Central. Association Between Recent Use of Proton Pump Inhibitors and Nontyphoid Salmonellosis: A Nested Case-Control Study A separate study looking at gastroenteritis more broadly also found elevated risk in PPI users.23PubMed Central. Proton pumps and gastroenteritis If you take a PPI daily, this does not mean you should stop it, but it does mean your margin for food safety errors is smaller than average, and extra care with food handling and cooking temperatures is worthwhile.
Person-to-Person Transmission and Chronic Carriers
Salmonella can pass directly between people, though this is a less common route than food or animal contact. The bacteria are shed in feces, so anyone who is infected and does not wash their hands thoroughly after using the bathroom can transmit it to others. This is a particular concern in settings like daycare centers, nursing homes, and hospitals, where close contact and shared facilities create more opportunities for fecal-oral spread.
Most people stop shedding the bacteria within weeks of recovering. A small number become chronic carriers, continuing to harbor and intermittently shed Salmonella for months or longer. Gallstones appear to play a role in long-term carriage. In a study of typhoid cases and their household contacts in Kenya, people with gallstones shed the bacteria for significantly longer periods than those without them.24PubMed Central. Fecal Shedding, Antimicrobial Resistance and In Vitro Biofilm formation on Simulated Gallstones by Salmonella Typhi Isolated from Typhoid Cases and Asymptomatic Carriers in Nairobi, Kenya The bacteria form biofilms on the surface of gallstones, creating a protected reservoir that is difficult for the immune system or antibiotics to clear. Chronic carriers are a particular concern for typhoid-causing strains, but the principle applies to nontyphoidal Salmonella as well.
Food Handlers and Commercial Settings
Restaurants, catering operations, and food processing facilities introduce their own layer of risk. When a food handler carrying Salmonella (whether symptomatic or not) prepares food without adequate hand hygiene, the bacteria can reach large numbers of people in a single sitting. Workers handling raw meat and those preparing ready-to-eat foods are particularly important links in the chain of transmission.25PubMed Central. Salmonella, Food Safety and Food Handling Practices
In processing plants, Salmonella’s ability to form biofilms on stainless steel, plastic, and rubber surfaces makes it especially stubborn. Standard cleaning can remove bacteria from flat, smooth surfaces, but biofilms tucked into crevices, gaskets, and worn equipment surfaces resist routine sanitation.1PubMed Central. Biofilm formation in food processing plants and novel control strategies to combat resistant biofilms: the case of Salmonella spp. This is one reason why occasional recalls of processed foods trace back to persistent contamination at a single facility that went undetected for weeks or months.
How Weather and Climate Affect Salmonella Risk
Salmonella infections follow a seasonal pattern nearly everywhere they are tracked, peaking in summer and early fall. Warmer ambient temperatures allow the bacteria to multiply faster in food that is left unrefrigerated, and outdoor cooking, picnics, and barbecues create more opportunities for temperature abuse.
The link goes beyond general seasonal trends. Research modeling Salmonella cases against climate data in the southern United States found a strong positive correlation between high temperatures and infection rates.26PubMed Central. Effects of Climate Change on Salmonella Infections A separate study in Maryland found that extreme heat events were associated with roughly a 4% increase in salmonellosis risk per event, with the increase more pronounced in coastal areas than inland.27PubMed Central. Climate change, extreme events and increased risk of salmonellosis in Maryland, USA: Evidence for coastal vulnerability Coastal vulnerability may reflect the fact that warming surface waters, flooding, and runoff carry the bacteria into recreational and irrigation water sources more readily.
For you personally, the takeaway is that the margin for error shrinks in hot weather. A grocery run that leaves raw chicken in a warm car for 30 minutes on a cool day is bad; in midsummer, it is considerably worse. The same applies to picnics, camping coolers, and buffets sitting out at outdoor events. Salmonella’s growth rate at 25°C dwarfs its growth at refrigerator temperatures, so the difference between safe and unsafe can come down to how quickly you get perishable food back into the cold.
Recreational Water and Travel
Swimming in or accidentally swallowing water from lakes, rivers, or unchlorinated pools is a less common but real route of exposure. Salmonella has been found in surface waters including rivers, lakes, and ponds, where it can persist for long periods.4PubMed Central. Presence and Persistence of Salmonella in Water: The Impact on Microbial Quality of Water and Food Safety Agricultural runoff carrying animal waste is one of the main ways it gets there. After heavy rains, pathogen levels in surface water can spike, which is why many public health advisories discourage swimming in natural water bodies shortly after storms.
Travel to regions with lower sanitation infrastructure increases risk further. Typhoid fever, caused by a different species of Salmonella than the nontyphoidal strains behind most food poisoning, is primarily a disease of contaminated water and food in areas where sewage treatment is limited. Travelers to South Asia, sub-Saharan Africa, and parts of Southeast Asia are at particularly elevated risk. Nontyphoidal Salmonella is everywhere, but the likelihood of encountering a large dose goes up wherever the cold chain for food is unreliable and water quality is inconsistent.
Reducing Your Practical Risk
Because Salmonella reaches people through so many routes, no single precaution eliminates risk entirely. But the interventions that matter most are straightforward:
- Cook thoroughly: Internal temperatures of at least 74°C (165°F) for poultry and 71°C (160°F) for ground meat kill Salmonella reliably in high-moisture foods. Eggs should be cooked until both yolk and white are firm.
- Refrigerate promptly: Get perishable foods into the refrigerator within two hours of purchase or preparation, and within one hour if the ambient temperature is above 32°C (90°F).
- Separate raw and ready-to-eat: Use different cutting boards for raw meat and foods that won’t be cooked, and wash hands, utensils, and surfaces with soap after handling raw animal products.
- Skip the chicken rinse: Cooking kills surface bacteria; rinsing just aerosolizes them across your kitchen.
- Wash hands after animal contact: This applies after handling reptiles, backyard poultry, pet food (especially raw), and any animal feces. Soap and water, not just hand sanitizer.
- Be cautious with raw doughs and batters: Both raw eggs and raw flour can carry Salmonella, and the low moisture of dough makes the bacteria harder to kill even with brief baking.
None of these steps is exotic. The challenge is consistency, especially in environments where you are cooking for a crowd, managing small children around pet animals, or storing food during a summer cookout. Salmonella exploits exactly the moments when food safety slips your mind.