Table 2. Linear regression analysis for influenza activities of previous season in the U.S. and input variables from the 40th week in 2010 to the 40th week in 2018.
| ILI for the U.S. after 26 week | |||||
|---|---|---|---|---|---|
| LR 1 Beta [P-value] |
LR 2 Beta [P-value] |
LR 3 Beta [P-value] |
LR 4 Beta [P-value] |
LR 5 Beta [P-value] |
|
| ILI—U.S. (before 26 week) | 0.857 [<0.001] | - | - | - | - |
| Total INF—Australia (present) | - | 0.005 [<0.001] | - | - | 0.001 [0.485] |
| Total INF—Chile (present) | - | 0.009 [<0.001] | - | - | 0.007 [<0.001] |
| GT INF A—Australia (present) | - | - | 0.059 [<0.001] | - | 0.043 [<0.001] |
| GT INF A—Chile (present) | - | - | 0.023 [<0.001] | - | -0.009 [<0.001] |
| Temp—U.S. (present) | - | - | - | 0.111 [<0.001] | 0.054 [<0.001] |
| Adj. R-squared | 0.537 | 0.761 | 0.720 | 0.557 | 0.865 |
| Total INF for the U.S. after 26 week | |||||
| ILI—U.S. (before 26 week) | 1.076 [<0.001] | - | - | - | - |
| Total INF—Australia (present) | - | 18.4 [<0.001] | - | - | -2.610 [0.012] |
| Total INF—Chile (present) | - | 23.6 [<0.001] | - | - | 26.8 [<0.001] |
| GT INF A—Australia (present) | - | - | 246.7 [<0.001] | - | 250.0 [<0.001] |
| GT INF A—Chile (present) | - | - | 49.8 [<0.001] | - | -24.9 [0.001] |
| Temp—U.S. (present) | - | - | - | 277.9 [<0.001] | - |
| Adj. R-squared | 0.475 | 0.729 | 0.839 | 0.286 | 0.887 |
| INF A for the U.S. after 26 week | |||||
| ILI—U.S. (before 26 week) | 0.900 [<0.001] | - | - | - | - |
| Total INF—Australia (present) | - | 16.3 [<0.001] | - | - | -3.415 [0.006] |
| Total INF—Chile (present) | - | 25.3 [<0.001] | - | - | 24.8 [<0.001] |
| GT INF A—Australia (present) | - | - | 169.6 [<0.001] | - | 182.7 [<0.001] |
| GT INF A—Chile (present) | - | - | 56.2 [<0.001] | - | -7.491 [0.261] |
| Temp—U.S. (present) | - | - | - | 219.9 [<0.001] | - |
| Adj. R-squared | 0.387 | 0.690 | 0.769 | 0.300 | 0.832 |
| INF B for the U.S. after 26 week | |||||
| ILI—U.S. (before 26 week) | 1.344 [<0.001] | - | - | - | - |
| Total INF—Australia (present) | - | 24.8 [<0.001] | - | - | 9.636 [<0.001] |
| GT INF A—Australia (present) | - | - | 74.9 [<0.001] | - | 54.4 [<0.001] |
| Temp—U.S. (present) | - | - | - | 58.0 [<0.001] | - |
| Adj. R-squared | 0.552 | 0.627 | 0.749 | 0.143 | 0.787 |
Beta, Beta coefficient; CI, Confidence Interval; GT, Google Trends; INF, Influenza; ILI, Influenza-like illness; LR, Linear regression; Temp, temperature; U.S., United States of America.
GT INF A—Australia is GT with the keyword of “influenza A virus” in Australia.