Table 3. Duration of each intensity category* in weeks for influenza seasons from 2009 to 2015 for the three parameters: proportion ILI, proportion positive and composite.
| Season** | Out of season (weeks) | Low (weeks) |
Moderate (weeks) | High (weeks) | Extraordinary (weeks) |
|---|---|---|---|---|---|
| Proportion ILI | |||||
| 2009/2010 | 21 | 9 | 15 | 4 | 3 |
| 2010/2011 | 25 | 15 | 12 | 0 | 0 |
| 2011/2012 | 21 | 17 | 14 | 0 | 0 |
| 2012/2013 | 36 | 8 | 7 | 1 | 0 |
| 2013/2014 | 29 | 16 | 7 | 0 | 0 |
| 2014/2015 | 27 | 16 | 9 | 0 | 0 |
| Proportion positive | |||||
| 2009/2010 | 26 | 18 | 8 | 0 | 0 |
| 2010/2011 | 26 | 14 | 12 | 0 | 0 |
| 2011/2012 | 28 | 11 | 9 | 4 | 0 |
| 2012/2013 | 29 | 13 | 10 | 0 | 0 |
| 2013/2014 | 27 | 15 | 7 | 3 | 0 |
| 2014/2015 | 38 | 7 | 6 | 1 | 0 |
| Composite | |||||
| 2009/2010 | 25 | 14 | 13 | 0 | 0 |
| 2010/2011 | 25 | 16 | 11 | 0 | 0 |
| 2011/2012 | 25 | 15 | 10 | 2 | 0 |
| 2012/2013 | 33 | 10 | 9 | 0 | 0 |
| 2013/2014 | 28 | 14 | 8 | 2 | 0 |
| 2014/2015 | 38 | 9 | 5 | 0 | 0 |
* Intensity category is raised/lowered on the first week each threshold is crossed except for the seasonal threshold in which intensity is raised/lowered when the threshold is crossed for two consecutive weeks.
** Starts on week 18 and ends on week 17 of the following year.