Norovirus is extraordinarily contagious, requiring as few as 18 viral particles to cause infection. For context, a single gram of stool from an infected person can contain billions of infectious doses. Protecting yourself comes down to a handful of specific habits around hand hygiene, surface cleaning, food preparation, and avoiding exposure during and after someone else’s illness.
Why Hand Sanitizer Isn’t Enough
The single most important thing you can do is wash your hands with soap and running water, and do it often. This is one case where alcohol-based hand sanitizer genuinely falls short. In laboratory testing, ethanol-based sanitizer reduced norovirus on hands by a negligible amount that wasn’t statistically different from doing nothing at all. Soap and water, by comparison, reduced viral contamination roughly three to ten times more effectively. Even a plain water rinse outperformed hand sanitizer.
The CDC is explicit on this point: hand sanitizer is not a substitute for handwashing when it comes to norovirus. You can use it as an extra step, but soap and water should always come first. Wash for at least 20 seconds, paying attention to fingertips and under nails, especially before eating, after using the bathroom, and after caring for someone who’s sick.
Cleaning Contaminated Surfaces
Norovirus can survive on countertops, doorknobs, light switches, and bathroom fixtures for days. Standard household cleaners won’t reliably kill it. Bleach is the go-to disinfectant: mix a solution of at least 1,000 parts per million sodium hypochlorite, which works out to roughly 5 tablespoons of regular household bleach per gallon of water. Prepare this fresh each day you need it, since the solution loses potency over time.
If bleach isn’t an option, look for products on the EPA’s List G, which are specifically registered as effective against norovirus. These include products based on hydrogen peroxide, hypochlorous acid, and certain quaternary ammonium compounds. The product label will indicate whether it’s approved for norovirus (technically tested against feline calicivirus, the accepted surrogate).
When someone vomits or has diarrhea, clean the area immediately and well beyond the visible mess. Wear disposable gloves, wipe up solids with paper towels, apply the bleach solution, and let it sit for at least 10 minutes before wiping it away. Dispose of the gloves and paper towels in a sealed plastic bag, then wash your hands.
How Norovirus Spreads Through the Air
Vomiting doesn’t just contaminate the immediate area. It launches tiny aerosol particles into the air, some small enough to remain suspended for dozens of minutes and travel across a room. Researchers studying a hotel restaurant outbreak found that the risk of infection correlated directly with how far diners were seated from the person who vomited. People sitting closer fell ill sooner than those farther away.
This means you should move away quickly if someone vomits nearby, and ventilate the space by opening windows if possible. In confined environments like cruise ships, classrooms, or shared offices, this airborne route helps explain why outbreaks spread so fast.
Cooking Temperatures That Kill Norovirus
Raw and undercooked shellfish, particularly oysters, are a well-known source of norovirus. Oysters filter large volumes of water and can concentrate the virus in their tissues. To eliminate norovirus, shellfish must reach an internal temperature of 90°C (194°F) and stay there for at least 90 seconds. Light steaming that just opens the shell is not sufficient.
Fruits and vegetables can also carry the virus if handled by an infected food worker or rinsed with contaminated water. Washing produce under running water helps but isn’t a guarantee. When outbreaks are circulating in your area, cooking vegetables rather than eating them raw reduces your risk. If you’re preparing food for others, avoid doing so while you’re sick or for at least two days after symptoms stop.
How Long a Sick Person Stays Contagious
One of the trickiest things about norovirus is that people remain contagious well beyond the 24 to 72 hours of active vomiting and diarrhea. Viral shedding in stool continues for several weeks after symptoms resolve. In people with weakened immune systems or other medical conditions, shedding can persist for months.
As a practical matter, the highest risk of transmission comes during active symptoms and the first few days of recovery. During this window, an infected person should avoid preparing food for others, ideally use a separate bathroom if available, and anyone cleaning up after them should treat every surface as contaminated. Shared towels and washcloths should be replaced with disposable paper towels during this period.
Handling Contaminated Laundry
Soiled clothing, towels, and bedding need special handling. Remove them carefully without shaking them out, which can disperse viral particles into the air. Wash on the hottest setting the fabric allows and use a machine dryer rather than line drying. If items are visibly soiled, pre-rinse them before putting them in the machine, and run a separate wash cycle rather than mixing them with other household laundry. Clean your hands thoroughly after handling dirty linens.
Why You Can Get It Again
Having norovirus once does not give you lasting protection. Natural immunity after an infection is short-lived, generally lasting months to a few years at most, and it only covers the specific strain you caught. With dozens of norovirus strains circulating and the virus constantly evolving, reinfection is common. There is currently no approved vaccine, though candidates are in early clinical trials. Prevention through hygiene and careful food handling remains the only reliable defense.
Quick Reference for High-Risk Situations
- Caring for someone sick: Wear disposable gloves for all cleanup, disinfect with bleach solution (5 tablespoons per gallon of water), and wash your hands with soap and water every time you leave the room.
- Traveling on a cruise or staying in a hotel: Wash hands before every meal, avoid buffet items that sit at room temperature, and skip raw oysters entirely.
- Shared living spaces (dorms, barracks, nursing homes): Disinfect high-touch surfaces like bathroom faucets, door handles, and shared appliances daily during an outbreak. Keep a dedicated bleach spray bottle on hand.
- After symptoms end: Continue rigorous handwashing for at least two weeks, avoid preparing food for others for a minimum of 48 hours, and launder all bedding and towels used during the illness on a hot cycle.