Key points
- Data on suspected and confirmed norovirus outbreaks reported to CDC by participating state health departments are updated monthly.
- NoroSTAT data is used to assess current and past norovirus activity and impact of future norovirus genotypes.
- NoroSTAT combines a subset of NORS and CaliciNet data.
About the current norovirus season
- During August 1–October 9, 2024, there were 98 norovirus outbreaks reported by NoroSTAT-participating states. During the same period last seasonal year, there were 105 norovirus outbreaks reported by these states.
- The total number of outbreaks reported during the 2024–2025 seasonal year is within the range reported during the same period during the 2012–2020 and 2021-2024 seasonal years.
Circulating norovirus genotypes
For norovirus genotypes currently circulating in the United States, see the data reported to CaliciNet.
Graph
Number of Suspected or Confirmed Norovirus Outbreaks Reported by NoroSTAT-Participating States Per Week, 2012–2025
Keep Reading:
NoroSTAT Data Table
What this graph shows:
The total number of suspected and confirmed norovirus outbreaks reported each week to CDC by the state health departments in Alabama, Colorado, Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, North Carolina, Ohio, Oregon, South Carolina, Tennessee, Virginia, and Wisconsin through the National Outbreak Reporting System (NORS) by week of illness onset, 2012–2025.
- Blue dashed line: Data from the 2020-2021 surveillance year. During the initial months of the COVID-19 pandemic, reported norovirus outbreaks fell to unusually low levels, and therefore have not been added to the pre-pandemic range.
- Gray area: Highest and lowest number of norovirus outbreaks reported each week for the 2012 through 2020 seasonal years (August–July).
- Blue area: Highest and lowest number of norovirus outbreaks reported each week for the 2021 through 2024 seasonal years (August–July). Outbreak data post-2021 are being monitored for changes to outbreak seasonality and trends.
- Solid red line: Latest data for the current seasonal year (2024-2025). State health departments participating in NoroSTAT have 7 business days to report norovirus outbreaks to CDC.
Graph trends
A seasonal year's line that consistently falls above the gray or blue areas, especially during the peak of the season (December to March), might indicate unusually high norovirus activity.