Assessment of influenza forecasts. The observed weekly incidence of influenza cases (circles) are compared against the predicted number of cases (lines). Filled circles represent the observed data that were used for prediction, and unfilled circles represent the observed data that was predicted using the proposed method. The unbroken line represents the expected prediction made using maximum likelihood estimates of the model parameters, and the dashed lines show the lower and upper 95% prediction intervals from the proposed uncertainty analysis. Panels A, B, C and D show the impact the different weeks (at weeks 15, 18, 21 and 24, respectively) on predictions of the future course of the epidemic. During the period of observation the unbroken line represents the conditionally expected values, while during the period of forecasting the line represents the conditionally predicted values. Week 0 on the horizontal axis corresponds to week 27 (week ending on 5 July 2009).