Every winter, “norovirus” is in the news. The US Centers for Disease Control and Prevention (CDC) describes norovirus as a very contagious virus that causes vomiting and diarrhea. Symptoms usually start 12 to 48 hours after exposure, and most people recover within 1 to 3 days. But you can still spread the virus for 2 weeks or more after you feel better. So the CDC says to stay home for 2 days (48 hours) after symptoms stop, and to wash hands with soap and water for at least 20 seconds. This sets out the CDC page “About Norovirus”.
1. Starts 12 to 48 hours after exposure; most recover in 1 to 3 days.
2. You can spread it for 2 weeks or more after feeling better — stay home 2 days (48 hours) after symptoms stop.
3. Wash hands with soap and water for at least 20 seconds, cook shellfish thoroughly, disinfect surfaces.
What it is — CDC
Norovirus causes acute gastroenteritis, inflammation of the stomach or intestines. The CDC notes it is not related to the flu, even though it is sometimes called a “stomach bug” (our reading).
Norovirus in numbers — CDC
| What | What the CDC says | Worth noting (our gloss) |
|---|---|---|
| When symptoms start | 12 to 48 hours after exposure | Not only yesterday’s meal |
| Recovery | Most within 1 to 3 days | — |
| Can spread it | 2 weeks or more after feeling better | Much longer than the illness |
| Stay home | 2 days (48 hours) after symptoms stop | Same 2 days as the NHS advice |
| Handwashing | Soap and water, at least 20 seconds | — |
“2 weeks or more” and “2 days at home” are different numbers: after the 2 days you go back to school or work, but keep washing your hands (our reading). The NHS advice is in diarrhoea and vomiting.
Symptoms — CDC
- Most common: diarrhea, vomiting, nausea, stomach pain
- Others: fever, headache, body aches
The main worry is dehydration. The CDC lists less urination, dry mouth and throat, and dizziness when standing up, and in children crying with few or no tears and unusual sleepiness or fussiness.
How much to drink is in daily water intake, and babies with vomiting and diarrhoea in baby vomiting and diarrhoea.
How it spreads — CDC
- Direct contact with someone who is ill — caring for them, sharing food or utensils, eating food they handled
- Eating or drinking contaminated food or liquids
- Touching contaminated surfaces and putting unwashed fingers in your mouth
The CDC says raw or undercooked shellfish such as oysters can make you ill. Anyone can get it, but children under 5, older adults and people with weakened immune systems are more likely to become seriously ill.
Prevention — CDC
| Step | What the CDC says | Worth noting (our gloss) |
|---|---|---|
| Hands | Soap and water for at least 20 seconds, often | Five steps in the handwashing post |
| Food | Cook shellfish thoroughly; wash fruit and vegetables | Relevant to winter oysters |
| Cleaning | Clean and disinfect contaminated surfaces | No product named on this page |
| Laundry | Wash in hot water | No temperature given here |
| When ill | Stay home | Until 2 days after symptoms stop |
The handwashing steps are in handwashing for 20 seconds. The page we read doesn’t name a disinfectant or a laundry temperature.
Checklist
- ☐ Drink often after vomiting or diarrhea; watch for dehydration
- ☐ Stay home 2 days (48 hours) after symptoms stop
- ☐ Keep washing hands with soap and water for at least 20 seconds
- ☐ Cook oysters and other shellfish thoroughly
- ☐ Clean and disinfect where someone was sick; hot-wash laundry
Questions that remain
Is hand sanitizer enough?
This page says to wash with soap and water. It doesn’t say how well sanitizer works against norovirus, so we haven’t either.
Does the flu vaccine help?
No. The CDC says norovirus is not related to the flu. Flu vaccination is covered in flu vaccination.
Sources
- CDC — About Norovirus — source (page shows: 24 April 2024; checked 13 October 2026). 12 to 48 hours, 1 to 3 days, 2 weeks or more, 2 days (48 hours), 20 seconds, symptoms and dehydration signs, spread, under 5, prevention.
- Not read. Korea Disease Control and Prevention Agency guidance and Korean case data.
- What we added. The “worth noting” column.
Where else to check
- Your doctor — if there are signs of dehydration, or a young child or older person is ill.
Written on 13 October 2026. The content is from the CDC; the glosses are ours. It does not replace diagnosis or treatment.
