Figure 1

Temporal trends of ILI incidence from IMS Health claims, CDC ILINet and Google Flu Trends (GFT) during the 2009-2010 pandemic flu show significant similarities. The total incidence of H1N1 pandemic as provided by GFT (blue line) and CDC (red dots) are plotted together with IMS claims data (black line). Note here that we used the strict definition of the flu (ICD9 codes: 486XX and 488XX). The temporal trends for the entire US are plotted in the center, followed by the 10 Human and Health Services (HHS) Regions shown around the US (HHS-I to HHS-X). In all the cases, the agreement between IMS claims data, GFT and CDC ILINet data is quantified by the correlation coefficient, depicted on the side of each panel. The numbers at the right hand side of every panel represent the correlation coefficient between the IMS claims and GFT data (top) and the IMS claims with ILINet data (bottom) respectively. These numbers represent all the data from the 52 weeks collected instead of measuring across the time segments for which CDC ILINet data was available. Note that CDC ILINet data has some missing values, removing these segments from our analysis actually improves the correlations (see Main Text for discussion). For HHS-IX and HHS-X, the CDC ILINet data was not fully available at the time of download and hence we have not shown the correlation values.