What is norovirus?
- 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.
- Take care in the kitchen.
- Carefully wash fruits and vegetables.
- Cook oysters and other shellfish thoroughly before eating them.
- 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.