Norwalk virus

Alternative names
Rotavirus infection; Viral gastroenteritis; Gastroenteritis - viral

Viral gastroenteritis is an inflammation of the stomach and intestines caused by a viral infection.

Causes, incidence, and risk factors
Viruses cause 30 to 40% of cases of infectious diarrhea in the U.S. and viral gastroenteritis is the second most common illness, after upper respiratory infections.

Many types of viruses can cause gastroenteritis but the most common are rotavirus and norwalk virus. Rotavirus is the leading cause of gastroenteritis in children and can also occur in adults exposed to children with the virus. Norwalk virus causes group-related or institutional diarrhea with peak frequency during the winter. Norwalk-like viruses are common in school-age children.

These viruses are often found in contaminated food or drinking water. The viruses cause about 40% of group-related diarrheal illnesses. They affect older children and adults and are more frequent during the winter months. Symptoms appear within 4 to 48 hours after exposure to the contaminated food or water. The viruses are usually spread by the fecal-oral route.

Rotavirus causes severe gastroenteritis in infants and young children. Severe dehydration and death can occur in the young age group. It is responsible for up to 50% of the hospitalizations of children with diarrhea. Outbreaks may also occur in geriatric settings such as nursing homes. By the age of 3 most children have acquired antibodies to the virus.

Gastroenteritis affects the young, the elderly, and immunosuppressed people most severely.


  • Abdominal pain  
  • Abdominal cramping  
  • Diarrhea  
  • Nausea  
  • Vomiting

Additional symptoms that may be associated with this disease:

  • Unintentional weight loss  
  • Vomiting blood (very rare)  
  • Excessive sweating  
  • Clammy skin  
  • Muscle pain  
  • Joint stiffness  
  • Incontinence  
  • Fever  
  • Chills  
  • Poor feeding

Signs and tests
Stool assays for the viruses can identify the specific agent. A stool culture may rule out bacterial causes of the illness.


The objective of treatment is to replace fluids and electrolytes (salt and minerals) lost by diarrhea. Antibiotic therapy is not effective in viral illness. Antidiarrheal medications are generally not given, as they may prolong the infectious process. Self-care measures to avoid dehydration include drinking electrolyte solutions (available over-the-counter) to replace fluids lost by diarrhea.

People with diarrhea who are unable to take fluids by mouth because of nausea may need intravenous fluids. This is especially true in small children.

People taking diuretics who develop diarrhea may be advised by their health care provider to stop taking the diuretic during the acute episode.


DO NOT give anti-diarrheal medications to children unless directed to do so by a health care provider. Since the risk of dehydration is greater in infants and young children, parents should closely monitor the number of wet diapers changed per day when the child is sick. Electrolyte and fluid replacement solutions for children are available in food and drug stores. Juice, soda or water do not replace electrolytes lost from vomiting or diarrhea. Children with diarrhea often benefit from dietary modifications until the diarrhea subsides.

Expectations (prognosis)
Most infections will resolve spontaneously. Children may become severely ill from dehydration caused by diarrhea.

Dehydration is the main complication. Rarely, severe reactions may occur.

Calling your health care provider
Call your health care provider if symptoms of dehydration occur, including low urine output, nausea, faintness or dizziness, dry mouth, sunken appearance to the eyes, sunken fontanelle (soft spot on an infant’s head), and confusion.

Also call if diarrhea persists for more than several days or if blood is noted in the stool.

Most infectious organisms are transmitted by unwashed hands. The best way to prevent viral gastroenteritis is to handle food properly and wash hands thoroughly after using the toilet.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.