The most effective way to avoid a stomach bug is frequent, thorough handwashing with soap and water, especially before eating and after contact with anyone who’s been sick. Most stomach bugs are caused by norovirus, which is extraordinarily contagious. It takes only a few viral particles to make you sick, and a single infected person sheds billions of them. That mismatch between how little it takes to get infected and how much virus is floating around explains why stomach bugs tear through households, schools, and cruise ships so quickly.
How Stomach Bugs Actually Spread
Norovirus travels by the fecal-oral route, which sounds straightforward but plays out in ways most people don’t think about. Microscopic particles of stool or vomit from an infected person end up in your mouth. That can happen when someone prepares your food without washing their hands, when you touch a contaminated doorknob and then eat a snack, or when tiny droplets from a vomiting episode spray through the air and land on nearby surfaces or even directly in your mouth.
Contaminated water is another route. Wells near leaking septic systems, improperly treated drinking water, and recreational water where someone has been sick can all carry the virus. Shellfish, especially oysters, are a well-known source because they filter large volumes of water and concentrate whatever’s in it.
Why It Spreads So Easily
Norovirus is built to survive. On hard surfaces like countertops, light switches, and plastic, it can remain infectious for more than two weeks. Even on soft surfaces like carpet or fabric, it stays viable for days to a week. That means a bathroom used by a sick person on Monday can still be a source of infection the following weekend if it hasn’t been properly disinfected.
People also remain contagious far longer than most realize. You can still spread the virus for two weeks or more after your symptoms disappear. If you have a weakened immune system or certain chronic conditions, viral shedding can continue for weeks to months. This is why outbreaks keep rolling through a household even after the first person feels fine.
Wash Your Hands With Soap, Not Sanitizer
This is the single most important prevention step, and there’s an important detail most people miss: alcohol-based hand sanitizer does not work well against norovirus. The CDC is clear that soap and water are more effective at removing norovirus than hand sanitizers. Norovirus lacks the outer fatty envelope that alcohol is good at dissolving, so even a high-quality sanitizer leaves the virus largely intact on your hands.
Wash with soap and running water for at least 20 seconds. Focus on the moments that matter most: before preparing or eating food, after using the bathroom, after changing a diaper, and after caring for someone who’s sick. If you’re in a situation where a stomach bug is going around, increase the frequency. Every time you touch a shared surface in a communal space, wash before your hands go near your face.
Disinfecting Surfaces Properly
Regular household cleaners and simple wiping are not enough to kill norovirus. You need a bleach solution at the right concentration. For active stomach bug situations, mix one cup of standard household bleach (the kind with 5.25% to 8.25% sodium hypochlorite) into ten cups of water. That creates a solution of roughly 5,000 parts per million of chlorine, which is what’s needed to destroy the virus.
The surface has to stay visibly wet with the solution for at least one full minute. If it dries before that minute is up, it didn’t work. Focus on high-touch areas: toilet handles, faucet knobs, light switches, doorknobs, remote controls, and phone screens. In a bathroom used by a sick person, disinfect after every episode of vomiting or diarrhea if possible.
Handling Food Safely
Norovirus is the leading cause of foodborne illness, and it usually gets into food through the hands of someone preparing it. If anyone in your household is sick or recently recovered, they should stay out of the kitchen entirely. Remember that two-week window of contagiousness after symptoms stop. That means the person who had the stomach bug last week can still contaminate dinner tonight.
Wash fruits and vegetables thoroughly under running water. Cook shellfish to a high internal temperature rather than eating it raw. Oysters are a particularly common vehicle for norovirus because they’re filter feeders often eaten raw or barely cooked.
Cleaning Up After Someone Gets Sick
When someone vomits or has diarrhea, the cleanup itself is a high-risk moment. Wear disposable gloves if you have them. Carefully remove any solid material with paper towels and dispose of it in a sealed plastic bag. Then disinfect the entire area with the bleach solution described above, extending well beyond the visible mess. Vomit sends tiny airborne droplets several feet in every direction.
For contaminated clothing, towels, or bedding, wash everything in the hottest water setting your machine offers, using detergent and the longest available cycle. For whites or items that won’t be damaged, add a small amount of bleach. Machine dry on high heat afterward. Handle soiled laundry carefully and avoid shaking it, which can release viral particles into the air.
Protecting Yourself During an Outbreak
If someone in your home is actively sick, your goal is to minimize every possible point of contact with the virus. Give the sick person their own bathroom if that’s an option. Assign them dedicated towels, cups, and utensils that no one else touches. Keep their door closed and let fresh air circulate through the space when possible.
Avoid sharing food, drinks, or eating utensils with anyone who’s been sick in the past two to three weeks. In communal settings like offices or dorms, be especially cautious about shared kitchens, bathrooms, and break rooms during outbreaks. Wash your hands before and after using any shared space, and carry your own water bottle rather than using shared fountains or dispensers.
If you’re traveling and hear about a stomach bug going around your hotel or ship, double down on hand hygiene, avoid buffet-style food where many hands have been near serving utensils, and stick to bottled water if you have any concerns about the local water treatment.