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Trends and Outbreaks


Each year on average in the United States, norovirus—

  • causes 19–21 million cases of acute gastroenteritis (inflammation of the stomach or intestines or both)
  • leads to 1.7–1.9 million outpatient visits and 400,000 emergency department visits, primarily in young children
  • contributes to about 56,000–71,000 hospitalizations and 570-800 deaths, mostly among young children and the elderly

You can get norovirus illness at any time during the year. But, it is most common in the winter. Also, there can be 50% more norovirus illness in years when there is a new strain of the virus going around.


Norovirus-associated Deaths

link to larger image for Figure 1A. Data from 1999–2007 show the number of U.S. deaths for norovirus-related illness is consistently higher during winter months. Deaths from norovirus were highest in winter of 2002–2003 and 2006–2007 when a new norovirus strain emerged..

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Outbreaks in health care facilities accounted for almost 63% of the norovirus outbreaks reported through the National Outbreak Reporting System from 2009 through 2012. 22% of outbreaks occurred in restaurants or banquet facilities. The remaining 15% of the reported outbreaks occurred in schools or day-care facilities, a private residence, or other settings.Most outbreaks of norovirus illness happen when infected people spread the virus to others. But, norovirus can also spread by consuming contaminated food or water and touching things that have the virus on them.

Healthcare facilities, including nursing homes and hospitals, are the most commonly reported places for norovirus outbreaks in the United States and other industrialized countries. Over half of all norovirus outbreaks reported in the United States occur in long-term care facilities.

Outbreaks of norovirus illness have also occurred in restaurants, schools, banquet halls, summer camps, cruise ships, and even at family dinners. These are all places where people often eat food handled or prepared by others.

In fact, norovirus is the leading cause of illness and outbreaks from contaminated food in the United States. About 50% of all outbreaks of food-related illness are caused by norovirus.

The total number of norovirus outbreaks by primary transmission mode from 2009 through 2012. The number of foodborne norovirus outbreaks were low in the summer months, the greatest number occurring in January. During the same time, the number of nonfoodborne always exceeded foodborne outbreaks and was low in the summer months and dramatically higher in the winter months.Foods that are commonly involved in outbreaks of norovirus illness are—

  • leafy greens (such as lettuce),
  • fresh fruits, and
  • shellfish (such as oysters).

But, any food that is served raw or handled after being cooked can get contaminated.

To search for foodborne outbreaks caused by norovirus, go to the Foodborne Outbreak Online Database (FOOD).

Norovirus outbreaks have also been caused by contaminated water from sewage in wells and recreational settings, such as pools.

Learn more about norovirus

Resources for Public Health Practitioners

For more information, see the “For Public Health Professionals” section of this Web site.

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