What is Norovirus?

Norovirus — what in the world? The very name strikes fear in the heart of businesses and patients alike. Recently, there have been reports of a “new strain” of norovirus, called “GII.Sydney,” becoming prominent since September 2012. What is going on? Is this some new superbug? Should we be afraid, or is it just a lot of media hype?

This transmission electron micrograph (TEM) reveals norovirus virions, or virus particles.

This transmission electron micrograph (TEM) reveals norovirus virions, or virus particles. (Photo Credit: Charles D. Humphrey, Centers for Disease Control and Prevention.)

In essence, norovirus is the virus that has caused the “stomach flu” for years — nothing more and nothing less. There are new strains that come in waves every few years, similar to mutations in the influenza virus. Despite that, we hear much more about it in media reports. As of January 2013, there is no evidence that this Australian strain, GII.Sydney, is more aggressive or dangerous than prior strains. According to the Centers for Disease Control, there are approximately 21 million cases of norovirus each year. The incubation period is between 12 and 48 hours, and patients may have vomiting, watery non-bloody diarrhea, abdominal cramps and nausea. Low-grade fever also occasionally occurs, and diarrhea is more common than vomiting in children. The majority of cases come from an infected person preparing food, but there can be person-to-person spread or transmission from contaminated surfaces.

One common question is, why are there outbreaks on cruise ships or in larger institutions? In each of these situations, there are a large number of people spending lots of time together, and they usually have a common food source. A single infected person can spread the illness to many people prior to having full-blown symptoms. Unfortunately, people can also pass on the virus for up to two weeks afterward. As a result, the cases tend to bounce around like pingpong balls dropped into a barrel.

Prevention is the name of the game. The best way to do this is by washing your hands frequently with soap and water. Alcohol-based hand sanitizers help but are not quite as good. Nonporous surfaces can be cleaned with bleach solutions. Usually, treatment with social measures, such as decreasing general social contact, quarantine of sick patients and strict hygiene measures, will stop an outbreak.

Treatment of norovirus is by general supportive measures. The most important item is early treatment with anti-vomiting medications and encouraging salty fluids like chicken soup or Gatorade. Stay home if possible and prevent dehydration. Many people say they don’t want to drink anything, because they are afraid it will make them throw up more. This is one of the biggest problems, so please be sure to contact your provider sooner rather than later if you think you have the stomach flu. If patients cannot keep fluids down or if they are lightheaded when standing, they need to go to the emergency department.

Another common question is whether you can get norovirus twice. A specific person contracts only one strain at a time and develops some immunity to that specific strain but is susceptible to any other strains. So effectively, yes, you can get it twice. If you would like to read more about norovirus, please see http://www.cdc.gov/norovirus/about/index.html

Guest blogger Leland Teng, MD, is a physician with the Lewis and John Dare Center. A version of this article originally appeared in the Dare Center Newsletter. For more information about the Dare Center, please visit VirginiaMason.org/dare or call (206) 341-1325.


  1. Reblogged this on Kira Moore's Closet and commented:
    This would be the little bugger…

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