New Strain of Norovirus
In 2012, a new strain of norovirus was detected in Australia. It is called GII.4 Sydney. People in the United States and other countries also have been infected with the new strain. It is currently the leading cause of norovirus outbreaks in the United States. However, we do not yet know if the new strain will cause more norovorus illness than in other years. It is still too early in the season to tell.
CDC will keep watching this new strain closely and provide more information when it is available.
Noroviruses are a group of related viruses. Infection with these viruses affects the stomach and intestines and causes an illness called gastroenteritis (GAS-tro-en-ter-I-tis; inflammation of the stomach and intestines).
Anyone Can Get Norovirus
Anyone can be infected with noroviruses and get sick. Also, you can get norovirus illness more than once during your life. The illness often begins suddenly. You may feel very sick, with stomach cramping, throwing up, or diarrhea.
Noroviruses are the most common cause of gastroenteritis in the United States. CDC estimates that each year more than 20 million cases of acute gastroenteritis are caused by noroviruses. That means about 1 in every 15 Americans will get norovirus illness each year. Norovirus is also estimated to cause over 70,000 hospitalizations and 800 deaths each year in the United States.
Many Names, Same Symptoms
You may hear norovirus illness called “food poisoning” or “stomach flu.” It is true that food poisoning can be caused by noroviruses. But, other germs and chemicals can also cause food poisoning. Norovirus illness is not related to the flu (influenza), which is a respiratory illness caused by influenza virus.
Symptoms of norovirus infection usually include diarrhea, throwing up, nausea, and stomach cramping.
Other, less common symptoms may include low-grade fever, chills, headache, muscle aches, and general sense of fatigue.
Norovirus illness is usually not serious. Most people get better in 1 to 2 days. But, norovirus illness can be serious in young children, the elderly, and people with other health conditions; it can lead to severe dehydration, hospitalization and even death.
You may get dehydrated if you are not able to drink enough liquids to replace the fluids lost from throwing up or having diarrhea many times a day. Symptoms of dehydration include a decrease in urination, a dry mouth and throat, and feeling dizzy when standing up. Children who are dehydrated may also cry with few or no tears and be unusually sleepy or fussy.
The best way to prevent dehydration is to drink plenty of liquids. Oral rehydration fluids are the most helpful for severe dehydration. But other drinks without caffeine or alcohol can help with mild dehydration. However, these drinks may not replace important nutrients and minerals that are lost due to vomiting and diarrhea.
If you think you or someone you are caring for is severely dehydrated, contact your doctor. For more information on norovirus and dehydration, see norovirus treatment.
Norovirus Spreads Quickly
Norovirus and Food
Norovirus is a leading cause of disease from contaminated foods in the United States. Foods that are most commonly involved in foodborne norovirus outbreaks include leafy greens (such as lettuce), fresh fruits, and shellfish (such as oysters). However, any food item that is served raw or handled after being cooked can become contaminated with noroviruses.
Norovirus can spread quickly from person to person in crowded, closed places like long-term care facilities, daycare centers, schools, hotels, and cruise ships. Noroviruses can also be a major cause of gastroenteritis in restaurants and catered-meal settings if contaminated food is served.
The viruses are found in the vomit and stool of infected people. You can get it by
- Eating food or drinking liquids that are contaminated with norovirus (someone gets stool or vomit on their hands, then touches food or drink).
- Touching surfaces or objects contaminated with norovirus and then putting your hand or fingers in your mouth.
- Having direct contact with a person who is infected with norovirus (for example, when caring for someone with norovirus or sharing foods or eating utensils with them).
People with norovirus illness are contagious from the moment they begin feeling sick until at least 3 days after they recover. But, some people may be contagious for even longer.
Norovirus: No Vaccine and No Treatment
There is no vaccine to prevent norovirus infection. Also, there is no drug to treat people who get sick from the virus. Antibiotics will not help if you have norovirus illness. This is because antibiotics fight against bacteria, not viruses. The best way to reduce your chance of getting norovirus is by following some simple tips.
Stop 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. If soap and water aren’t available, use an alcohol-based hand sanitizer. These alcohol-based products can quickly reduce the number of germs on hands in some situations, but they are not a substitute for washing with soap and water.
Take care in the kitchen
Carefully wash fruits and vegetables, and cook oysters and other shellfish thoroughly before eating them.
Do not prepare food while infected
People with norovirus illness should not prepare food for others while they have symptoms and for 3 days after they recover from their illness. (see For Food Handlers: Norovirus and Working with Food)
Clean and disinfect contaminated surfaces
After throwing up or having diarrhea, immediately clean and disinfect contaminated surfaces by using a bleach-based household cleaner as directed on the product label. If no such cleaning product is available, you can use a solution made with 5 tablespoons to 1.5 cups of household bleach per 1 gallon of water.
Wash laundry thoroughly
Immediately remove and wash clothing or linens that may be contaminated with vomit or stool. Handle soiled items carefully—without agitating them—to avoid spreading virus. If available, wear rubber or disposable gloves while handling soiled clothing or linens and wash your hands after handling. The items should be washed with detergent at the maximum available cycle length and then machine dried.
- CDC Norovirus web site
- Norovirus Treatment
- Norovirus Trends and Outbreaks
- For Food Handlers: Norovirus and Working with Food
- Norovirus in Healthcare Settings, general information on norovirus and prevention in healthcare facilities
- Handwashing: Clean Hands Save Lives, hand- and water-related hygiene tips
- Put Your Hands Together [PODCAST – 3:48 minutes], information on how to help stop the spread of infection and stay healthy
- Foodborne Burden
- Tips for Healthy Cruising
- CDC’s Vessel Sanitation Program
- Epidemiology of Foodborne Norovirus Outbreaks, United States, 2001–2008. Emerg Infect Dis[Internet]. 2012 Oct
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