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Table 5 Start and stop weeks of influenza season using various definitions from 1986–87 to 1990–91 influenza seasons by United States regions. Patients in the study were enrolled from a study site within one of the four regions.

From: Comparing estimates of influenza-associated hospitalization and death among adults with congestive heart failure based on how influenza season is defined

Region Year First last isolate 10% moving average 5% moving average 5% all isolates
   Start Stop Start Stop Start Stop Start Stop
Central 86–87 49 17 51 5 50 9 51 7
Northeast   44 11 50 5 49 6 50 4
South   45 16 53 9 51 10 1 6
West   45 8 51 5 48 6 52 5
Central 87–88 46 22 4 18 3 21 4 13
Northeast   1 22 7 14 6 23 8 13
South   50 25 4 14 3 14 4 13
West   52 20 2 3 1 9 2 11
Central 88–89 47 19 2 12 1 15 3 10
Northeast   47 18 2 18 1 18 4 10
South   50 19 51 15 51 20 3 11
West   51 17 8 10 4 13 3 13
Central 89–90 47 17 51 11 50 12 52 9
Northeast   48 21 1 11 52 12 2 10
South   48 12 50 12 50 13 51 8
West   46 11 3 6 52 9 51 8
Central 90–91 48 19 5 14 3 14 4 13
Northeast   45 22 3 10 50 17 3 8
South   40 19 1 16 51 19 3 8
West   52 21    5 9 5 12