Figure 1. State estimation using the six filters and synthetic ‘truth’.

The model-filter framework includes two model state variables and four model parameters: (A) the number of susceptible persons S, (B) the number of infected persons I, (C) the immunity period L, (D) the infectious period D, (E) the maximum reproductive number R_0max, and (F) the minimum reproductive number R_0min. The synthetic ‘truth’ for I and S was generated with the SIRS model, for a population of 100,000, with fixed parameters: L = 3.86 y, D = 2.27 d, R_0max = 3.79, and R_0min = 0.97; each model-filter framework was run repeatedly 25 times, with the same set of test data (i.e., synthetic ‘truth’ for the I time series plus random noise, shown as ‘x’ points in (B)). The green lines are the synthetic ‘truth’, blue lines are the mean trajectory over the 25 runs, and the grey areas around them delineate the 95% confidence interval.