Norovirus (formerly referred to as Norwalk virus) is an intestinal infection that causes what many people call the common “stomach flu.” It usually involves an intense bout of vomiting, nausea and diarrhea that lasts for a couple of days. In the United States, norovirus outbreaks are relatively common, especially in the winter, though they can occur at any time of the year. In 2017, norovirus outbreaks were reported to the Centers for Disease Control and Prevention (CDC) in nine states: Ohio, Oregon, Massachusetts, Michigan, Minnesota, South Carolina, Tennessee, Virginia and Wisconsin. Here are a few things to know about norovirus, including norovirus symptoms, incubation period and treatment. 1. Norovirus is the most common cause of the “stomach flu.” Norovirus is the most common cause for acute gastroenteritis, aka the “stomach flu,” causing more than 19 to 21 million cases in the U.S. every year. 2. Norovirus symptoms last for one to three days. Common norovirus symptoms include watery diarrhea, nausea, vomiting and abdominal cramps, which most people develop within 12 to 48 hours after exposure to the virus. 3. The virus spreads quickly. It takes fewer than 100 norovirus particles to make you sick. And those who are sick with norovirus illness shed billions of particles in their stool and vomit, making it easy to infect many other people in a very short period of time. That’s why staying in close quarters (a hotel, nursing home or cruise ship) or attending daycare or preschool puts your family at greater risk. The virus spreads if you have direct contact with an infected person, eat contaminated foods, drink contaminated liquids, or touch a contaminated object and then put your hands in or around your mouth. 4. Norovirus has a long incubation period. As soon as you begin feeling sick with norovirus, you’re contagious—and you can continue spreading the virus for several days after you recover. What’s more, the virus can remain on infected surfaces for weeks, and some disinfectants may not kill it. 5. You can get norovirus more than once. There are lots of different strains of norovirus, which means just because you’ve had it before doesn’t mean you won’t get sick with it again. 6. Infection can cause serious complications, usually from dehydration. While most people recover from norovirus without treatment, every year 56,000 to 71,000 people—mostly young kids and the elderly—are hospitalized in the U.S., and 570 to 800 die as a result of infection. The most common complication of norovirus-related diarrhea and vomiting is moderate to severe dehydration. So if you’re suffering from norovirus and experiencing symptoms of dehydration—including dry mouth, fatigue, less frequent urination, urine that’s dark yellow, headache, and muscle cramps—check in with your doctor. Watch out for unusual fussiness and crying without tears in babies and young children. 7. There is no norovirus treatment. Since norovirus is a virus, not bacteria, antibiotics don’t work on it. And there is no vaccine that protects against norovirus infection. 8. Wash your hands frequently and thoroughly to protect yourself. Since norovirus spreads easily when you touch contaminated surfaces, it’s important to always wash your hands thoroughly after using the restroom and before eating or handling food. Apply soap and scrub the front and back of your hands and between your fingers for at least 20 seconds (the time it takes to sing “Happy Birthday” in your head). Rinse and dry completely. Although alcohol-based hand sanitizers can do the job in a pinch, it’s best to rely on soap and water when both are available. 9. About 50% of all food-related illness is related to norovirus contamination. Be sure to wash all vegetables (especially leafy greens) and fruits before eating, as these are most commonly involved in norovirus outbreaks. That said, any food that’s not properly washed or cooked can get contaminated. So check the health inspection ratings of the restaurants you frequent, particularly during norovirus outbreaks. 10. Rest and hydration is the best norovirus treatment. Unfortunately there is currently no norovirus treatment. Your best bet: rest and drink plenty of fluids to prevent dehydration. If you’ve got younger kids who are sick, oral rehydration liquids (like Pedialyte) can help. Avoid sugary beverages, such as fruit juice and soda, which can make diarrhea worse. Your doctor may also recommend taking an anti-diarrheal medication. A bland diet (bananas, rice, potatoes, crackers, yogurt and soup) can help reduce nausea and vomiting. 11. If you or a family member is sick, take extra precautions to contain the virus. Anyone who’s ill with norovirus should try to stay at home and avoid cooking. Handle with care any sheets or towels that have come into contact with vomit or diarrhea, machine washing them at maximum length and heat, and drying in the dryer (not air drying). Immediately clean any other infected surfaces with a blend of 15 tablespoons household chlorine bleach per one gallon of water.