Table 2.
Correlation of weekly ILI visit percentage between the Indian Health Service Influenza Awareness System and ILINet at seven Indian Health Service facilities that reported to both systems between April 4, 2009 and January 2, 2010
| Facility State | Mean weekly visits (IHS) | ILINet peak (%) | Week | IHS peak (%) | Week | Peak offset (weeks)* | Spearman correlation (r)† | p Value |
|---|---|---|---|---|---|---|---|---|
| AL | 31 | 3.6 | Jan 2 | 18.2 | Nov 21 | 6 | 0.13 | 0.52 |
| AZ | 1352 | 10.6 | Sep 12 | 12.8 | Sep 12 | 0 | 0.77 | <0.001 |
| NM1 | 235 | 16.6 | Oct 17 | 6.2 | Oct 10 | 1 | 0.52 | 0.001 |
| NM2 | 305 | 19.4 | Oct 10 | 25.6 | Oct 3 | 1 | 0.86 | <0.001 |
| OK1 | 116 | 8.8 | Oct 17 | 9.1 | Oct 10 | 1 | 0.42 | 0.02 |
| OK2 | 98 | 33.3 | Oct 10 | 6.7 | Sep 12 | 4 | 0.37 | 0.03 |
| WY | 248 | 12.3 | Oct 24 | 13.2 | Oct 17 | 1 | 0.38 | 0.08 |
| All | 2723 | 9.1 | Oct 17 | 8.8 | Oct 10 | 1 | 0.66 | <0.001 |
*Difference, in weeks, of peak ILI percentage visit between the two reporting systems.
†The higher the correlation coefficient, the more similar the two systems in reporting.
HIS, Indian Health Service; ILI, influenza-like illness; ILINet, Influenza-like Illness Surveillance Network.