🦠 Norovirus
Norovirus is the world's most common cause of acute gastroenteritis — the "stomach bug" — responsible for 685 million illnesses globally each year. It spreads through contaminated food, water, surfaces, and person-to-person contact, and is extraordinarily resistant to standard alcohol disinfectants. There is no approved vaccine or antiviral treatment.
Key facts
- Causes ~21 million illnesses and ~900 deaths per year in the U.S. (CDC)
- As few as 18 viral particles can cause infection
- No FDA-approved vaccine or antiviral as of 2026
- Alcohol hand sanitizers are largely ineffective — soap and water required
Most-asked questions
- What are norovirus symptoms?
- How does norovirus spread?
- How do you prevent norovirus?
- How long is norovirus contagious?
- Does hand sanitizer kill norovirus?
These questions are answered in depth on NorovirusQuestions.com.
What is norovirus?
Norovirus belongs to the genus Norovirus within the family Caliciviridae. It is a non-enveloped RNA virus classified into at least seven genogroups, with GII.4 responsible for the majority of global outbreaks. Its lack of a lipid envelope makes it unusually resistant to alcohol-based disinfectants — a property that distinguishes it from influenza, coronaviruses, and most other common respiratory viruses. (CDC: About Norovirus)
How norovirus spreads
Norovirus spreads through four primary routes: direct person-to-person contact, contaminated food (particularly raw shellfish and ready-to-eat foods touched by infected food handlers), contaminated water, and contaminated surfaces. Its infectious dose is exceptionally low — as few as 18 viral particles can cause illness — and it can survive on hard surfaces for days to weeks. (CDC: Norovirus Transmission)
Critically, alcohol hand sanitizers do not work well against norovirus regardless of concentration. The CDC recommends soap-and-water handwashing as the preferred hand hygiene method whenever norovirus exposure is possible.
Who is most at risk?
Norovirus affects people of all ages, but severe outcomes — including hospitalization and death — are concentrated in adults aged 65 and older and immunocompromised individuals. High-risk settings include long-term care facilities (65% of U.S. reported outbreaks), restaurants and food-service operations, schools, childcare centers, and cruise ships. The virus peaks during fall and winter months. (CDC: Norovirus Trends & Outbreaks)
Prevention
There is no approved norovirus vaccine. Prevention relies on hygiene and disinfection practices — and choosing the right products matters:
- Wash hands with soap and water for at least 20 seconds — especially after using the toilet, before preparing food, and after caring for someone who is ill.
- Use bleach-based disinfectants on hard surfaces — many common disinfectants (alcohol wipes, quat sprays) are not effective against norovirus without a bleach ingredient.
- Cook shellfish thoroughly — raw or undercooked oysters, clams, and mussels are a significant norovirus risk.
- Isolate ill individuals — stay home for at least 48 hours after symptoms resolve; continue careful handwashing for 2+ weeks after recovery.
- Wash contaminated laundry in hot water and dry on high heat; handle soiled items with gloves.
How Norovirus compares to other viruses
A case fatality rate on its own is hard to read — 38% sounds catastrophic, 0.1% sounds trivial, and neither tells you how the virus sits against anything else. This section places Norovirus against the other viruses in the network's 15-virus dataset, which is maintained here on the hub rather than on any single-virus site.
- Annual Exposure / Cases 19,000,000–21,000,000 1 higher, 9 lower, of 11 reporting this
- Annual Deaths 900 3 higher, 6 lower, of 10 reporting this
3 of the five metrics are not published for Norovirus — severe outcome rate, hospitalization rate, case fatality rate. Those cells are left empty rather than estimated. A blank is not a low number: it means the measurement does not exist, and reading it as zero would make the least-studied diseases look like the safest ones.
In-depth answers at NorovirusQuestions.com
Complete pages on symptoms, transmission, treatment, prevention, outbreaks, FAQ, cruise ship guidance, food safety, and a preparedness buying guide. Reviewed monthly against CDC and WHO guidance.
This page provides a summary of norovirus. For comprehensive information, visit NorovirusQuestions.com. Summarized from CDC and WHO guidance (WHO covers norovirus in its food-safety fact sheet; it publishes no norovirus-specific one). Last reviewed: .