Norovirus Infection

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Norovirus infection facts

  • Norovirus is a small virus that is highly contagious between humans.
  • People acquire the virus by ingesting material contaminated with small amounts of infected feces or fluids. Food and water may be contaminated during processing or handling.
  • Noroviruses are the most common cause of gastroenteritis in the United States.
  • Infected people usually experience vomiting or watery diarrhea or both.
  • The illness usually lasts two to three days and resolves by itself.
  • There is no specific treatment for norovirus, but it is important that infected people stay well hydrated. Fluids containing sugar and electrolytes should be encouraged. Intravenous fluids may be needed if the person cannot maintain an adequate oral intake of fluids.
  • Complications are usually related to the degree of dehydration. Young children and the elderly are at special risk for dehydration.
  • Because the disease is highly contagious, it is important for caretakers to clean their hands whenever they come into contact with the ill person or their environment.
  • The risk of food-borne outbreaks or outbreaks within hospitals or nursing homes may be minimized by following established standards that include hand hygiene.

What is a norovirus?

A norovirus is a small virus that contains RNA and is surrounded by a protein coating. By sequencing the RNA, scientists have discovered that there are many different types of norovirus. Originally, strains were named based on the city in which they were first identified. Thus, one common strain used to be called Norwalk virus. Based on genetic typing, we now know that there are at least 25 different strains of norovirus that affect humans. The RNA genome in noroviruses apparently is easily mutated to produce new norovirus types.

Norovirus infection is the most common cause of gastroenteritis outbreaks in the U.S. Although some people call this the "stomach flu," norovirus is not related to the influenza virus. According to statistics from the CDC, there are 21 million cases of norovirus infection annually in the U.S., of which one-quarter are related to food-borne outbreaks. Outbreaks occur throughout the year but are more common in the winter months. There is no specific treatment for norovirus. Fortunately, the disease is self-limited and simple supportive measures are sufficient to care for most people unless they become dehydrated. Outbreaks can occur almost anywhere in the world. In 2012, a new strain named GII.4 Sydney was identified. Since the first outbreak, the virus was quickly detected in New Zealand, France, and the U.S. It has caused about half of the norovirus infections detected in 2012-2013 in the U.S. A new outbreak of norovirus occurred at Yellowstone National Park, causing illness in about 200 visitors and camp employees in June 2013.

Medically Reviewed by a Doctor on 9/27/2013

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Norovirus Infection - Symptoms Question: What were the symptoms associated with a norovirus infection in you or someone you know?
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Learn why outbreaks of norovirus infection (stomach flu) seem to happen so frequently on cruise ships.

Norovirus Infection: A Cause for Travelers' Concern?

Many people may not be familiar with the term norovirus, but it's actually a relatively new term for an old disease. The many strains of noroviruses cause a self-limited gastrointestinal illness that many refer to as the "stomach flu." Outbreaks of norovirus infection have also been documented as coming from restaurants, schools, and nursing homes.


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