What is gastroenteritis?
Gastroenteritis—the "stomach flu" or "stomach bug"—is usually an acute infection of the gut. In adults the most common cause is norovirus, and bacterial food poisoning from undercooked meat or eggs or contaminated food (Salmonella, Campylobacter) is also common (Riddle et al., 2016). Despite the nickname, it has nothing to do with influenza.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
How do viral and bacterial gastroenteritis differ?
| Viral | Bacterial | |
|---|---|---|
| Typical causes | Norovirus, rotavirus | Salmonella, Campylobacter, pathogenic E. coli |
| Pattern | Lots of vomiting, better in 1–3 days | High fever, severe cramps, possibly bloody stools |
| Antibiotics | Don't help | Only for some severe cases |
A dry mouth, much less urine, dizziness or feeling wiped out are signs of dehydration. Get care for bloody diarrhea, fever above 101.3°F (38.5°C), severe belly pain, vomiting so bad you can't keep fluids down, or if the patient is elderly, a young child or immunocompromised.
How is it treated and prevented?
The key is replacing fluids and electrolytes. For mild cases, water and sports drinks are fine; for more fluid loss, sip an oral rehydration solution (ORS) a little at a time. Resume easy-to-digest food as soon as you can. Most people don't need antibiotics, and anti-diarrheal drugs should be avoided with bloody diarrhea or high fever (Shane et al., 2017). Norovirus holds up against alcohol sanitizer, so washing hands with soap and cooking food thoroughly are the best prevention.
FAQ
- Should I stop eating?
- No need to fast for long. Focus on fluids first, then start bland foods as soon as you can keep them down.
- How long is the stomach flu contagious?
- Norovirus spreads very easily through vomit, stool and contaminated hands or food. Avoid preparing food for others for at least two days after symptoms end.
Sources reviewed: 2026-10-25
References
- Riddle, M. S., DuPont, H. L., & Connor, B. A. (2016). ACG clinical guideline: Diagnosis, treatment, and prevention of acute diarrheal infections in adults. American Journal of Gastroenterology, 111(5), 602–622.
- Shane, A. L., Mody, R. K., Crump, J. A., et al. (2017). 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clinical Infectious Diseases, 65(12), e45–e80.