Sequential data assimilation of the stochastic SEIR epidemic model for regional COVID-19 dynamics

Ralf Engbert; Maximilian M. Rabe; Reinhold Kliegl; Sebastian Reich

Statistical modeling of trends and weekly oscillations Mean certified cases, computed across regions per day, reveal a strong daily profile with local minima always falling on Sundays. The corresponding mean of log contact parameters reveals the same oscillation. The negative slopes are compatible with the expectation that a decrease in contact rates causes a decrease in daily cases; they are also present when heterogeneity between regions is taken into account with linear mixed models. These illustrative analyses imply two considerations. If evaluated against statistics of daily cases, obviously containment measures must take the weekly cycle into account and avoid confounds in 11 . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. the design. There are many potential sources for this cycle, some of them possibly quite trivial (e.g., the number of tests carried out, a bias against hospital visits on weekends and in favor of a GP visit during the week, etc.). However, if experimental research and statistical modeling can establish that part of these fluctuations are indeed due to reduced contact rates beyond the family context on weekends, then dynamical models may help with the prediction of the timing of tightening and loosening decisions in local contexts. For example, one may consider moving to a three-or fourworkday week for some time, in well-defined contexts, and in targeted regions to facilitate this dynamic.