Merck Manual

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Norovirus Gastroenteritis


Jonathan Gotfried

, MD, Lewis Katz School of Medicine at Temple University

Reviewed/Revised Jun 2023
Topic Resources

Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. It can be caused by the norovirus.

  • Norovirus is very contagious and spreads from person to person.

  • Typically, people have diarrhea, vomiting, and abdominal cramps.

  • The diagnosis is based on a person’s history of recent contact with contaminated food, water, or people infected with the virus; recent travel; and sometimes laboratory tests.

  • Thoroughly washing the hands after a bowel movement or contact with fecal matter and avoidance of undercooked foods and contaminated water are the best ways to prevent infection.

  • Fluids are usually the only treatment needed, but some people may be given medications to help stop diarrhea.

Norovirus infects people of all ages. It is now the most common cause of gastroenteritis in the United States in all age groups, including children (peak age is between 6 months and 18 months).

Infections occur year-round in the United States, but most occur from November to April. Most people are infected after swallowing contaminated food or water.

Because norovirus is highly contagious, infection can easily be spread from person to person. This virus causes most cases of gastroenteritis epidemics on cruise ships and in nursing homes.

Symptoms of Norovirus Gastroenteritis

Norovirus typically causes vomiting, abdominal cramps, and diarrhea. Children have more vomiting than diarrhea, whereas adults have more diarrhea. Symptoms start 1 to 2 days after infection and last 1 to 3 days.

People may also have fever, headache, and body aches.

Diagnosis of Norovirus Gastroenteritis

  • A doctor's evaluation

  • Sometimes stool tests

The diagnosis of norovirus is usually based on typical symptoms, especially if an outbreak is currently ongoing. Sometimes other family members or coworkers have recently been ill with similar symptoms. Other times, norovirus can be traced to contaminated water or inadequately cooked, spoiled, or contaminated food. Recent travel, especially on a cruise ship, may give clues as well.

To confirm the diagnosis of norovirus, doctors sometimes test stool specimens.

Treatment of Norovirus Gastroenteritis

  • Fluids and rehydration solutions

  • Sometimes medications


Usually the only treatment needed for norovirus gastroenteritis is getting bed rest and drinking an adequate amount of fluids. Even a person who is vomiting should drink as much as can be tolerated, taking small frequent sips.

If vomiting or diarrhea is prolonged or the person becomes severely dehydrated, fluids and electrolytes given by vein (intravenously) may be needed. Because children can become dehydrated more quickly, they should be given fluids with the appropriate mix of salts and sugars. Any of the commercially available solutions designed to replace lost fluids and electrolytes (called oral rehydration solutions Treatment Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more ) are satisfactory. Carbonated beverages, teas, sports drinks, beverages containing caffeine, and fruit juices are not appropriate. If the child is breastfed, breastfeeding Breastfeeding Breast milk is the ideal food for newborns and infants. Although babies may be fed breast milk or formula, the World Health Organization (WHO) and American Academy of Pediatrics (AAP) recommend... read more Breastfeeding should continue.

As the symptoms subside, the person may gradually add foods to the diet. Although often recommended, there is no need to limit the diet to bland foods such as cereal, gelatin, bananas, rice, applesauce, and toast. However, some people are unable to tolerate milk products for a few days after having diarrhea.


If the diarrhea continues for 24 to 48 hours and there is no blood in the stool to indicate a more serious bacterial infection, the doctor may prescribe a medication to control the diarrhea, such as diphenoxylate, or instruct the person to use an over-the-counter medication, such as loperamide. These medications (called antidiarrheal medications) are not given to children under 18 years of age with acute diarrhea. Antidiarrheal medications are also not given to people who have recently used antibiotics, who have bloody diarrhea, who have small amounts of blood in the stool that are too small to be seen, or who have diarrhea and fever.

Antibiotics and antiviral medications are not given.

Prevention of Norovirus Gastroenteritis

  • Handwashing

  • Avoiding high-risk food and beverages

Good hygiene practices are important at all times, not just when there is an outbreak of gastroenteritis.

Because most norovirus infections are transmitted by person-to-person contact, particularly through direct or indirect contact with infected stool, good handwashing with soap and water after a bowel movement is the most effective means of prevention. If soap and clean water are unavailable, an antibacterial hand sanitizer should be used.

To prevent foodborne infections, hands should be washed before touching food, knives and cutting boards used to cut raw meat should be washed before use with any other food, meat and eggs should be cooked thoroughly, and leftovers should be refrigerated promptly after cooking. Only pasteurized dairy products and pasteurized apple juice should be used.

Travelers should try to avoid high-risk foods and beverages, such as those sold by street vendors.

To prevent recreational water illness, people should not swim if they have diarrhea. Infants and toddlers should have frequent diaper checks and should be changed in a bathroom and not near the water. Swimmers should avoid swallowing water while swimming.

For prevention in children, caregivers should wash their hands thoroughly with soap and water before preparing bottles for formula-fed infants. They should also wash their hands after changing diapers. Diaper-changing areas should be disinfected with a freshly prepared solution of household bleach (¼ cup bleach diluted in 1 gallon of water).

Children with diarrhea should not go to a day care center until their symptoms are gone.

Did You Know...

  • It takes 20 seconds to receive the full benefit of handwashing with regular soap and water.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Cafcit, NoDoz, Stay Awake, Vivarin
Anti-Diarrheal, Imodium A-D, Imodium A-D EZ Chews , K-Pek II
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