How are the percent changes (blue, red, gray color gradients) on the map calculated?
The Distribute project displays a color gradient map that shows whether ILI emergency visit activity for the current week in each region is increasing or decreasing. The map shows the percent change (up or down) of the current week of ILI activity compared to the annual weekly average during the 2009-2010 influenza season (2009-2010 baseline). Due to the early emergence of the A/H1N1 pandemic, the 2009-2010 baseline period is measured from August 1, 2009 through July 31, 2010.
