A foodborne illness is any sickness caused by eating contaminated food or drink. It’s extremely common: an estimated 48 million people in the United States get sick from contaminated food every year, leading to 128,000 hospitalizations and 3,000 deaths. Most cases are mild and resolve on their own, but certain pathogens and certain people face much higher stakes.
How Contaminated Food Makes You Sick
Foodborne illness works through two basic mechanisms. In one type, called an infection, you swallow live bacteria, viruses, or parasites that multiply inside your digestive tract and attack the intestinal lining. Salmonella and norovirus work this way. In the other type, called intoxication, bacteria produce a toxin either in the food itself (before you eat it) or inside your gut after you swallow them. Staphylococcal food poisoning is a classic example of intoxication: the toxin is already in the food, which is why symptoms can hit within hours.
Some toxins trigger your intestines to flood with fluid, causing watery diarrhea. Others destroy cells in the gut wall, leading to bloody diarrhea and inflammation. The botulism toxin takes a different path entirely: it’s absorbed from the gut into the bloodstream and blocks nerve signals to muscles, which can cause paralysis. The specific pathogen determines what symptoms you get, how quickly they appear, and how dangerous the illness can be.
Common Pathogens Behind Outbreaks
Bacteria, viruses, and parasites all cause foodborne illness, but a handful of organisms are responsible for the vast majority of cases.
Norovirus is the single biggest driver of foodborne illness in the U.S. It spreads easily through contaminated produce (especially leafy greens), and symptoms typically start 12 to 48 hours after exposure. It causes intense vomiting and diarrhea that usually resolve within a couple of days.
Salmonella is the leading bacterial cause, with symptoms appearing 6 to 48 hours after eating contaminated food. It’s commonly linked to poultry, eggs, and produce. Children under 5 are three times more likely to be hospitalized from a Salmonella infection than older kids or adults.
E. coli O157:H7 has a longer incubation period of 1 to 8 days and is particularly dangerous for young children. Kidney failure strikes 1 out of 7 children under age 5 who are diagnosed with this strain.
Listeria is less common but far more deadly. Initial gut symptoms can appear within 9 to 48 hours, but the more serious invasive form of the disease can take 2 to 6 weeks to develop. It disproportionately affects pregnant women, older adults, and people with weakened immune systems.
Symptoms and Warning Signs
The most common symptoms are diarrhea, stomach cramps, nausea, vomiting, and fever. These overlap almost entirely with what people call “stomach flu,” which makes it hard to tell the two apart. The key difference is the source: foodborne illness comes from something you ate, while viral gastroenteritis typically spreads person to person through close contact.
Most cases clear up within a day or two without treatment. But certain symptoms signal something more serious: bloody diarrhea, diarrhea lasting more than 3 days, a fever above 102°F, vomiting so frequent you can’t keep liquids down, or signs of dehydration like dizziness when standing, dry mouth, or very little urination.
Who Faces the Greatest Risk
Anyone can get food poisoning, but four groups face significantly higher odds of severe illness because their bodies are less equipped to fight off infections.
- Adults 65 and older. The immune system weakens with age. Nearly half of older adults with lab-confirmed Salmonella, Campylobacter, Listeria, or E. coli infections end up hospitalized.
- Children under 5. Their immune systems are still developing, and diarrhea can quickly lead to dangerous dehydration in small bodies.
- Pregnant women. Pregnancy shifts the immune system in ways that increase vulnerability. Pregnant women are 10 times more likely to develop a Listeria infection than the general population.
- People with weakened immune systems. This includes people with diabetes, liver or kidney disease, HIV, autoimmune conditions, or anyone receiving chemotherapy or radiation. People on dialysis, for instance, are 50 times more likely to get a Listeria infection.
Foods Most Likely to Carry Contamination
Produce is responsible for roughly 46% of all foodborne illnesses in the U.S., with leafy vegetables topping the list. That may surprise people who assume raw chicken is the main culprit. Salads, pre-washed greens, sprouts, and fresh fruits are common vehicles because they’re often eaten raw, giving pathogens no chance to be killed by heat.
Meat and poultry account for about 22% of illnesses but a disproportionate 29% of deaths, largely driven by Listeria and Salmonella infections linked to poultry. Dairy and eggs contribute to roughly 20% of illnesses. Fish and shellfish make up a smaller share at around 6%, but raw or undercooked shellfish carries concentrated risk.
How to Prevent Food Poisoning at Home
Most foodborne illness is preventable with four basic habits: clean, separate, cook, and chill.
Clean
Wash your hands with soap and water for at least 20 seconds before, during, and after preparing food. Wash cutting boards, utensils, and countertops with hot soapy water after each food item. Rinse fresh fruits and vegetables under running water, even if you plan to peel them.
Separate
Keep raw meat, poultry, and seafood away from other foods at every stage: in your shopping cart, in the refrigerator, and on the counter. Use one cutting board for raw meat and a separate one for produce and ready-to-eat foods. Store raw meat in sealed containers so juices can’t drip onto other items.
Cook
A food thermometer is the only reliable way to know food is safe. Color and texture are not accurate indicators. The safe internal temperatures to remember: 165°F for all poultry and leftovers, 160°F for ground meats, and 145°F for whole cuts of beef, pork, lamb, and fish (let whole cuts rest 3 minutes before eating).
Chill
Bacteria multiply fastest between 40°F and 140°F, a range food safety experts call the “danger zone.” At those temperatures, bacteria can double in number in as little as 20 minutes. Keep your refrigerator at 40°F or below and your freezer at 0°F or below. Refrigerate perishable food within 2 hours of cooking or buying it, or within 1 hour if the temperature outside is above 90°F. Never thaw frozen food on the counter. Use the refrigerator, cold water, or a microwave instead.