Figure 1.

Real-time estimates (‘nowcasting’) of the unweighted percentages of weekly outpatient visits for influenza-like illness (ILI) in the USA between 3 January 2010 and 21 September 2013. Nowcasting models are forecasting models that estimate current levels of influenza, before the release of official data one week later. (a) Out-of-sample nowcasts using ILI data from the previous week and Google search query data from the current week, for a sliding training window of Δt=16 weeks. (b) In-sample nowcast errors for the baseline model, using ILI data from the previous week only, and the advanced model, using ILI data from the previous week and Google search query data from the current week. (c) Out-of-sample nowcast errors for the baseline model and the advanced model for Δt=16 weeks.