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NoroSTAT Data

Suspected and Confirmed Norovirus Outbreaks Reported by State Health Departments in Massachusetts, Michigan, Minnesota, Ohio, Oregon, South Carolina, Tennessee, Virginia, and Wisconsin to the National Outbreak Reporting System (NORS) by Week of Illness Onset, 2009-2017*†.

The number of norovirus outbreaks reported to NORS is typically higher in winter months, peaking in December, January, and February. However reported outbreaks in 2013-2014 peaked in April and in 2014-2015 peaked in March, with an additional increase in April.

See data table for this chart.

What this graph shows:

  • This graph tracks the total number of suspected and confirmed norovirus outbreaks reported each week by states participating in NoroSTAT.
  • The gray area represents the highest and lowest number of norovirus outbreaks reported each week for the 2009 through 2015 seasonal years (August–July).
  • The green dotted line is data from the last seasonal year (2015-2016).
  • The solid red line is the latest data for the current seasonal year (2016-2017). State health departments participating in NoroSTAT have 7 business days to report norovirus outbreaks to CDC.
  • A seasonal year’s line that consistently falls above the gray area, especially during the peak of the season (December to March), might indicate unusually high norovirus activity.

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More information about the current norovirus season:

  • Since August 1, 2016, there have been 1201 norovirus outbreaks reported by NoroSTAT-participating states. During the same period last year, there were 1128 norovirus outbreaks reported by these states.
  • The number of outbreaks reported this seasonal year to date is within the range reported during the same period over the previous 7 years.
  • To see what norovirus genotypes are currently circulating in the United States visit the CaliciNet data page.

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