Written and reviewed by Emily W., PhD · Last reviewed: May 23, 2025
Most viral stomach bugs in healthy adults last 24 to 72 hours. Norovirus — the most common cause in the US — typically runs 12 to 60 hours. It is intense but short.
The typical course
| Stage | Timing | What happens |
|---|---|---|
| Incubation | 12–48 hours after exposure | No symptoms |
| Onset | Hour 0–6 | Sudden nausea, then vomiting |
| Peak | Hour 6–24 | Vomiting and diarrhea, cramps, sometimes low fever |
| Turning point | Hour 24–48 | Vomiting stops, diarrhea continues |
| Recovery | Day 2–4 | Appetite returns, stools normalise |
| Tail | Day 4–14 | Mild loose stools and food sensitivity possible |
That tail phase surprises people. The gut lining takes a week or two to fully repair, so temporary lactose intolerance and loose stools after the main illness are normal.
How long you stay contagious
This is the important part. With norovirus, you continue shedding virus in stool for at least two weeks after symptoms end, and you are most contagious during symptoms and for the first 48 hours after they stop.
Practical guidance: do not prepare food for others for at least 48 hours after symptoms stop, ideally 72. Food handlers in most US states are required to stay off work for a set period — check your local health department rules.
Also worth knowing: alcohol-based hand sanitizer does not reliably kill norovirus. Soap and water for 20 seconds does. For surfaces, a diluted bleach solution works where standard household cleaners may not.
Is it a virus or food poisoning?
Timing is the best clue. Food poisoning from bacterial toxins often starts within 1 to 6 hours of eating and tends to be shorter. Viral gastroenteritis takes 12 to 48 hours to appear and spreads person to person. Our full comparison is in norovirus versus food poisoning.
What to drink and eat
First 12 hours, if vomiting: small sips only. A tablespoon of fluid every 10 minutes is better tolerated than a glass every hour. Plain water, oral rehydration solution, or diluted sports drink.
Once vomiting settles: add plain starchy foods. Toast, rice, crackers, bananas, plain potatoes. The old BRAT diet is not essential but the principle — bland, low-fat, low-fibre — holds.
Avoid for a few days: dairy, fried food, alcohol, caffeine, and very sugary drinks, which can worsen diarrhea by drawing water into the gut.
Oral rehydration solution beats plain water when losses are heavy, because it replaces sodium and potassium too. You can buy sachets cheaply at any pharmacy.
Should you take anti-diarrhea medication?
Loperamide can help adults with watery diarrhea and no fever, particularly if you need to travel or work. Do not use it if you have a high fever or blood in your stool — in bacterial infections, slowing the gut can keep the infection in longer.
Anti-nausea medication is prescription-only in most cases and can be worth a telehealth call if vomiting will not stop.
Dehydration is the real risk
Nearly all serious outcomes from stomach bugs in healthy adults come from fluid loss, not the infection itself. Watch for dark urine, urinating less than every 8 hours, dizziness on standing, dry mouth, and unusual drowsiness. See signs of dehydration in adults for the full list.
When to get medical help
Call a doctor for symptoms lasting more than three days, inability to keep any fluid down for 12 hours, blood in vomit or stool, severe abdominal pain, a fever above 102°F, or signs of dehydration.
Get urgent care sooner if you are over 65, pregnant, have diabetes, kidney disease, or a weakened immune system. If you have diabetes, read sick day rules for diabetes before you get ill — vomiting changes how you should handle your medication.
Go to the emergency room for persistent vomiting with no urine output, confusion, or severe one-sided abdominal pain. See vomiting that will not stop for the full guidance.
Related reading
- Norovirus vs Food Poisoning: How to Tell the Difference
- Signs of Dehydration in Adults: When You Need Medical Help
- Sick Day Rules for Diabetes: What to Do When You Are Ill
Sources
- Centers for Disease Control and Prevention
- MedlinePlus — U.S. National Library of Medicine
- U.S. Food and Drug Administration
Medical disclaimer: This article is for general information only and is not a substitute for advice from a qualified healthcare professional. It should not be used to diagnose or treat a health problem. Always speak to your doctor or pharmacist about your own situation. If you think you may have a medical emergency, call 911 or go to your nearest emergency department.
