To ensure this assessment of surveillance data was comparable to the study that validated Google Flu Trends [2] , we performed a secondary analysis replicating methods from that study with our dataset. The mean coefficient of correlation between Google Flu Trends and CDC ILI Surveillance was calculated over nine US Census Regions for the 2007-08 influenza season. The mean coefficient of correlation between Google Flu Trends and CDC Virus Surveillance was calculated similarly for comparison.