NoroSTAT Data

What this graph shows:

  • The total number of suspected and confirmed norovirus outbreaks reported each week by states* participating in NoroSTAT.
  • The gray area: highest and lowest number of norovirus outbreaks reported each week for the 2012 through 2020 seasonal years (August–July).
  • The green dotted line: data from the last seasonal year (2020-2021).
  • The solid red line: latest data for the current seasonal year (2021-2022). 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.

Number of Suspected or Confirmed Norovirus Outbreaks Reported by
NoroSTAT-Participating States Per Week, 2012-2022

The number of norovirus outbreaks reported to NORS is typically higher in winter months, peaking in December, January, and February. However reported outbreaks in 2015-2016 peaked in April and in 2016-2017 peaked in March, with an additional increase in April.

See data table for this chart.

*reported by the state health departments in Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, Ohio, Oregon, South Carolina, Tennessee, Virginia, Wisconsin, and Wyoming to CDC through the National Outbreak Reporting System (NORS) by week of illness onset, 2012-2022.

More information about the current norovirus season:

  • During August 1, 2021 – June 18, 2022, there were 878 norovirus outbreaks reported by NoroSTAT-participating states. During the same period last seasonal year, there were 307 norovirus outbreaks reported by these states.
  • The total number of outbreaks reported during the 2021-22 seasonal year is below the range reported during the same period over the previous 8 years.
  • To see what norovirus genotypes are currently circulating in the United States visit the CaliciNet data page.