Reassessing Google Flu Trends Data for Detection of Seasonal and Pandemic Influenza: A Comparative Epidemiological Study at Three Geographic Scales
Figure 3
Scatter plots of weekly excess influenza-like illness (ILI) visit proportions against updated Google Flu Trends (GFT) model search query estimates, 2003–2013.
Weekly excess percent-ILI is calculated as Serfling estimates subtracted from observed proportions. Plots show updated GFT model estimates compared with weighted CDC ILI-Net data for (A) the United States, and (B) Mid-Atlantic HHS-2 Region States (New Jersey, New York), and local ILI surveillance from emergency department ILI visit data for (C) New York City. Plots are shown for weeks June 1, 2003 to April 25, 2009 (grey circles), April 26 to January 2, 2010 (red diamonds), January 3, 2010 to Oct 6, 2012 (grey squares), and October 7, 2012 to March 30, 2013 (blue triangles). Lines representing equivalent axes for X = Y are shown (grey dashed line). Regression lines are shown for the 2003/2004–2008/2009 seasons (black line), 2009 pandemic (red line), 2010/2011–2010/2012 seasons (grey solid line) and the 2012/2013 season (blue line).