Norovirus is a virus that causes illness of the same name. Norovirus illness is commonly called other names such as viral gastroenteritis, stomach flu, and food poisoning.
Norovirus infection causes acute gastroenteritis (inflammation of the stomach and intestines).
The most common symptoms are watery diarrhea, explosive projectile vomiting (that shoots out), and stomach pain.
Anyone can get norovirus, and can have the illness multiple times in their lifetime.
The sources of norovirus are people (specifically, the feces and vomit of infected individuals), as well as raw or undercooked shellfish.
How serious is a norovirus illness?
People with norovirus can feel extremely ill and experience vomiting or diarrhea many times a day.
Most people get better within 1 to 2 days.
Dehydration can be a problem among some people, especially the very young, the elderly, and people with other illnesses.
How contagious is norovirus?
Norovirus illness is highly contagious. As few as 10 viral particles can cause infection; the average stool or vomit volume can contain over 100 million particles.
People with norovirus are contagious from the moment they begin feeling ill to anywhere from 3 days to 2 weeks after they have recovered.
Norovirus can survive in the environment for long periods of time. It can survive freezing conditions and heat exposure up to 140°F.
Norovirus can spread rapidly in closed environments like dormitories, daycare centers, prisons, cruise ships, and nursing homes.
How is norovirus spread?
The virus is spread by contaminated individuals touching items or handling food, or through vomit or feces of infected individuals.
The illness is spread when people:
Eat food or drink liquids that are contaminated with norovirus.
Touch surfaces or objects that are contaminated with norovirus, and then place their hand in their mouth.
Have direct contact with an infected person — such as caring for or sharing food, drinks, or eating utensils with an infected person.
How can I prevent the spread of norovirus?
Practice proper hand hygiene:
Wash your hands carefully with soap and water, especially after using the toilet and changing diapers, and always before eating or preparing food.
Alcohol-based hand sanitizers (containing at least 62% ethanol) may be a helpful addition to hand washing, but they are not a substitute for washing with soap and water. See CDC's Handwashing: Clean Hands Save Lives.
Don't prepare food while infected. People who are infected with norovirus should not prepare food for others while they have symptoms and for 3 days after they recover from their illness.
Wash laundry thoroughly.
Immediately remove and wash clothing or linens that may be contaminated with vomit or fecal matter.
Handle soiled items carefully, without agitating them, to avoid spreading virus.
Wash items with detergent at the maximum available cycle length and then machine dry.
Clean and disinfect contaminated surfaces, especially after an episode of vomiting or diarrhea, with a solution of bleach and water. Some recommended strengths are:
1 tablespoon of bleach per gallon of water for stainless steel, food/mouth contact items, and toys.
1/3 cup of bleach per gallon of water for non-porous surfaces such as tile floors, counter-tops, sinks, and toilets.
1½ cups of bleach per gallon of water for pourous surfaces such as wooden floors.
Is there specific treatment or vaccine for norovirus?
There is no vaccine to prevent norovirus infection, although this is an area of active research.
There is no specific drug to treat people with norovirus illness.
Rehydration is important for infected people — they must drink plenty of liquids to replace fluid lost through vomiting and diarrhea. In some cases, fluids may need to be given intravenously.
