What is the difference between food poisoning and a stomach bug?

Food poisoning typically develops within hours of eating contaminated food and causes severe symptoms, while a stomach bug (gastroenteritis) develops gradually over 1-3 days and spreads from person to person through viruses or bacteria.

According to the Centers for Disease Control and Prevention (CDC), food poisoning results from consuming contaminated food or beverages containing harmful bacteria like Salmonella, E. coli, or Campylobacter. Symptoms usually appear within 1-6 hours after eating and include sudden onset of severe nausea, vomiting, diarrhea, and abdominal cramps. The illness typically resolves within 24-48 hours once the contaminated food passes through your system.

A stomach bug, medically known as viral gastroenteritis, is caused by viruses such as norovirus or rotavirus that spread through contact with infected individuals or contaminated surfaces. The CDC reports that stomach bugs have a gradual onset, with symptoms developing over 12-72 hours. Initial symptoms often include fatigue and mild nausea, progressing to vomiting, diarrhea, and stomach pain. These illnesses typically last 1-3 days but can persist up to a week.

The key distinguishing factors include timing and transmission. Food poisoning strikes quickly after eating a specific meal and affects only those who consumed the contaminated food. You can often pinpoint the exact food source. Stomach bugs spread contagiously and may affect multiple family members or coworkers over several days, even if they didn't eat the same foods.

Symptom severity also differs. Food poisoning often causes more intense, sudden symptoms with severe cramping and frequent vomiting. Stomach bugs tend to produce milder but longer-lasting symptoms with gradual onset. Food poisoning may also cause fever less frequently than viral gastroenteritis.

For example, if you develop severe nausea and vomiting within 2-4 hours of eating potato salad at a picnic, and others who ate the same dish become ill, this suggests food poisoning. However, if you gradually feel unwell over a day, then develop stomach symptoms, and your family members become sick days later, this indicates a contagious stomach bug.

Both conditions require similar treatment focusing on rest, hydration, and avoiding solid foods until symptoms improve. Seek medical attention if you experience severe dehydration, high fever above 102°F, blood in vomit or stool, or symptoms persisting beyond 72 hours.

Related: Digestive Health · When should persistent stomach symptoms be checked medically? · What habits support better digestion throughout the day? · Can overeating stretch the stomach and worsen symptoms?