Non-typhoidal salmonella (NTS) refers to the large group of Salmonella bacteria that cause food poisoning, as opposed to the small number of strains that cause typhoid fever. There are more than 2,600 different varieties (called serovars) of Salmonella, and the vast majority of them fall into the non-typhoidal category. In the United States alone, NTS causes an estimated 1.28 million illnesses every year, making it the leading cause of foodborne illness deaths at 238 per year.
How NTS Differs From Typhoid Salmonella
Though they belong to the same species, non-typhoidal and typhoidal Salmonella behave very differently in the human body. Typhoidal strains (the ones behind typhoid and paratyphoid fever) have adapted to infect only humans. They spread person to person, cause a slow-building systemic illness with a 7 to 21 day incubation period, and can turn people into long-term carriers for a year or more.
Non-typhoidal strains are generalists. They live in farm animals, wild birds, reptiles, and pets, and they reach humans mainly through contaminated food. Once swallowed, NTS bacteria trigger a strong inflammatory response in the gut lining, recruiting waves of immune cells that typhoidal strains deliberately avoid provoking. That intense gut inflammation is why NTS typically causes obvious digestive symptoms within hours, while typhoid fever creeps in slowly with fever, chills, and sometimes no diarrhea at all.
Common Strains
Out of roughly 1,500 non-typhoidal serovars known to infect people, two dominate worldwide. Salmonella Enteritidis is the most common, accounting for about 42% of human isolates in large surveillance studies. Salmonella Typhimurium comes in second at around 11%. Despite “Typhimurium” in the name, this strain is not the one that causes typhoid fever. A closely related variant called S. I 4,[5],12:i:- has been rising in frequency in recent years and now ranks third in many countries. Other notable strains include Dublin, Heidelberg, and Agona, which circulate primarily in livestock and poultry production.
How You Get Infected
NTS bacteria live in the intestines of a wide range of animals. They reach your plate through several well-documented routes:
- Raw or undercooked poultry and meat, the single most common vehicle for outbreaks
- Raw or undercooked eggs, because bacteria can be present inside the shell before it forms
- Unpasteurized dairy products, including raw milk and soft cheeses
- Fresh produce, contaminated through irrigation water, soil, or handling
- Pet reptiles and birds, which carry the bacteria on their skin, feathers, and in their droppings
Cross-contamination in the kitchen is a major factor. Cutting raw chicken on a board and then using the same surface for salad, or not washing your hands after handling a pet turtle, can easily transfer enough bacteria to cause illness.
What Happens in Your Body
After you swallow contaminated food, the bacteria need to survive your stomach acid. If enough of them make it through, they invade the cells lining your small intestine. Once inside those cells, they trigger a powerful inflammatory response. Your immune system floods the area with infection-fighting cells, which damages the intestinal lining and pulls fluid into the gut. That combination of inflammation and fluid loss is what produces diarrhea, cramping, and nausea.
In healthy adults, the infection stays confined to the gut. Your immune system clears the bacteria within several days, and symptoms resolve on their own in under 10 days. The incubation period is short, typically 6 to 24 hours after eating contaminated food, so most people can trace their illness back to a recent meal.
Symptoms and Timeline
The hallmark symptoms of NTS gastroenteritis are watery diarrhea, abdominal cramps, nausea, and vomiting. Many people also develop a fever. Symptoms usually appear within 6 to 24 hours of exposure and peak within the first two to three days. Most people feel significantly better within a week, though bowel habits may take a bit longer to fully normalize.
The biggest immediate risk is dehydration, especially in young children and older adults who lose fluids quickly. Signs to watch for include dry mouth, dark urine, dizziness when standing, and in children, a lack of tears when crying.
When the Infection Spreads Beyond the Gut
In most healthy people, NTS stays in the digestive tract. But in people with weakened immune systems, very young children, older adults, and people with conditions like HIV or sickle cell disease, the bacteria can cross into the bloodstream. This is called invasive non-typhoidal salmonella disease, and it’s far more serious.
A global review of invasive NTS cases found that blood infection (bacteremia) occurred in over 57% of invasive cases, and septic shock developed in about 11%. Other complications included bone infections (osteomyelitis) in about 2.5% of cases, joint infections in about 2.8%, abscesses in about 3%, and lung infections in roughly 8%. Rarer but life-threatening complications included inflammation of the heart valves (endocarditis), brain inflammation, and weakening of blood vessel walls. These numbers reflect hospitalized invasive cases, not the typical bout of food poisoning, but they underscore why certain populations need closer medical attention.
Treatment
For the vast majority of NTS infections, the only treatment needed is staying hydrated. That means water, broth, or oral rehydration solutions. The illness is self-limiting, and your immune system handles the bacteria on its own. Antibiotics are reserved for people with severe intestinal illness or those at high risk for invasive disease, such as infants, people over 65, and those with compromised immune systems. Using antibiotics unnecessarily can actually prolong the time you shed bacteria in your stool and contributes to growing antibiotic resistance in Salmonella strains.
Preventing Infection
Proper cooking kills NTS bacteria reliably. The key internal temperatures to remember:
- Poultry (all cuts, ground): 165°F (73.9°C)
- Ground beef, pork, or veal: 160°F (71.1°C)
- Steaks, chops, and roasts (beef, pork, lamb): 145°F (62.8°C), then rest for 3 minutes
- Eggs: 160°F (71.1°C), or cook until both yolk and white are firm
- Fish and shellfish: 145°F (62.8°C)
Beyond cooking temperatures, the basics matter: wash hands thoroughly after handling raw meat or touching pets (especially reptiles and birds), use separate cutting boards for raw protein and ready-to-eat foods, refrigerate leftovers within two hours, and avoid unpasteurized milk and juice. Washing fruits and vegetables under running water removes surface contamination, though it won’t eliminate bacteria that have been absorbed into the produce through contaminated irrigation.