NoroSTAT Data Table
The following table shows data on suspected and confirmed norovirus outbreaks reported to CDC by state health departments participating in the NoroSTAT network. States report through the National Outbreak Reporting System (NORS) and outbreaks are classified by week of illness onset, 2012-2023. The NoroSTAT network includes Alabama, Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, North Carolina, Ohio, Oregon, South Carolina, Tennessee, Virginia, Wisconsin, and Wyoming.* Data from the NoroSTAT network are typically released online on a monthly basis.
Norovirus Outbreaks Reported by State Health Departments by Week of Illness Onset, 2012-2023
| Week | Minimum, 2012-20 | Maximum, 2012-20 | Range, 2012-20 | 2020-21 | 2021-22 | 2022-23 |
|---|---|---|---|---|---|---|
| 1-Aug | 1 | 10 | 9 | 0 | 2 | 6 |
| 8-Aug | 2 | 17 | 15 | 1 | 2 | 3 |
| 15-Aug | 3 | 12 | 9 | 0 | 4 | 6 |
| 22-Aug | 4 | 10 | 6 | 2 | 1 | 5 |
| 29-Aug | 0 | 12 | 12 | 1 | 4 | 2 |
| 5-Sep | 4 | 9 | 5 | 0 | 3 | 7 |
| 12-Sep | 5 | 14 | 9 | 1 | 4 | 7 |
| 19-Sep | 4 | 11 | 7 | 1 | 7 | 9 |
| 26-Sep | 4 | 17 | 13 | 0 | 3 | 6 |
| 3-Oct | 2 | 14 | 12 | 1 | 5 | 6 |
| 10-Oct | 4 | 16 | 12 | 0 | 8 | 10 |
| 17-Oct | 4 | 17 | 13 | 0 | 2 | 8 |
| 24-Oct | 4 | 16 | 12 | 1 | 7 | 9 |
| 31-Oct | 11 | 26 | 15 | 0 | 7 | 11 |
| 7-Nov | 6 | 26 | 20 | 2 | 6 | 11 |
| 14-Nov | 14 | 26 | 12 | 0 | 7 | 10 |
| 21-Nov | 10 | 40 | 30 | 0 | 5 | 11 |
| 28-Nov | 27 | 59 | 32 | 1 | 15 | 9 |
| 5-Dec | 33 | 64 | 31 | 1 | 12 | 19 |
| 12-Dec | 25 | 84 | 59 | 0 | 28 | 13 |
| 19-Dec | 14 | 55 | 41 | 0 | 11 | 12 |
| 26-Dec | 23 | 69 | 46 | 1 | 15 | 19 |
| 2-Jan | 29 | 91 | 62 | 5 | 14 | 36 |
| 9-Jan | 28 | 66 | 38 | 3 | 7 | 26 |
| 16-Jan | 31 | 90 | 59 | 3 | 15 | 25 |
| 23-Jan | 40 | 83 | 43 | 4 | 33 | 29 |
| 30-Jan | 43 | 65 | 22 | 14 | 44 | 38 |
| 6-Feb | 41 | 71 | 30 | 9 | 42 | 50 |
| 13-Feb | 34 | 61 | 27 | 17 | 68 | 47 |
| 20-Feb | 23 | 69 | 46 | 9 | 56 | 47 |
| 27-Feb | 32 | 78 | 46 | 13 | 101 | 56 |
| 6-Mar | 32 | 65 | 33 | 21 | 54 | 43 |
| 13-Mar | 32 | 51 | 19 | 20 | 71 | 57 |
| 20-Mar | 11 | 55 | 44 | 26 | 61 | 27 |
| 27-Mar | 10 | 57 | 47 | 20 | 53 | 41 |
| 3-Apr | 6 | 56 | 50 | 28 | 58 | 32 |
| 10-Apr | 1 | 33 | 32 | 30 | 37 | 22 |
| 17-Apr | 1 | 32 | 31 | 24 | 35 | 15 |
| 24-Apr | 3 | 28 | 25 | 17 | 38 | 25 |
| 1-May | 2 | 27 | 25 | 17 | 30 | 15 |
| 8-May | 0 | 28 | 28 | 19 | 22 | |
| 15-May | 0 | 31 | 31 | 14 | 16 | |
| 22-May | 0 | 18 | 18 | 6 | 9 | |
| 29-May | 0 | 12 | 12 | 11 | 4 | |
| 5-Jun | 0 | 11 | 11 | 8 | 1 | |
| 12-Jun | 2 | 12 | 10 | 5 | 4 | |
| 19-Jun | 1 | 12 | 11 | 8 | 8 | |
| 26-Jun | 1 | 9 | 8 | 6 | 6 | |
| 3-Jul | 2 | 10 | 8 | 5 | 2 | |
| 10-Jul | 1 | 13 | 12 | 11 | 7 | |
| 17-Jul | 0 | 11 | 11 | 4 | 2 | |
| 24-Jul | 2 | 11 | 9 | 3 | 4 |
*Notes:
- Michigan and South Carolina joined the NoroSTAT network at the start of the 2015-16 seasonal year; 2012-15 data from these states have been added for comparison.
- Massachusetts and Virginia joined the NoroSTAT network at the start of the 2016-17 seasonal year; 2012-16 data from these states have been added for comparison.
- New Mexico and Wyoming joined the NoroSTAT network at the start of the 2018-19 seasonal year; 2012-2018 data from these states have been added for comparison.
- Nebraska joined the NoroSTAT network at the start of the 2019-20 seasonal year; 2012-2019 data from this state have been added for comparison.
- Alabama and North Carolina joined the NoroSTAT network at the start of the 2022-23 seasonal year; 2012-2022 data from these states have been added for comparison.