A framework for counterfactual analysis, strategy evaluation, and control of epidemics using reproduction number estimates
Fig 3
A) Daily confirmed cases at UIUC during Fall 2020 and Spring 2021. We mark five shaded areas for five important events across the two semesters, corresponding to the entry screening of Fall 2020 (I), the start of the Big Ten football season (II), Christmas Break (III), the entry screening of Spring 2021 (IV), and Spring Break (V). The simulated spreading process (dotted solid line) accurately captures the spreading trend observed on the UIUC campus during Fall 2020 and Spring 2021, including spikes and weekly confirmed pattern. We simulate the spreading process over Fall 2020 and Spring 2021 separately, since at the beginning of each semester, the entry-screening resets the spreading process. B) Estimated effective reproduction number for UIUC from Fall 2020 to Spring 2021. The estimated effective reproduction number (95% confidence interval) is greater than one during multiple periods, particularly at the beginning of Fall 2020, around the middle of October 2020, and the middle of Spring 2021, corresponding to the three events marked by Shaded Areas I, II, and V in Fig 3A. The effective reproduction number aligns with the confirmed cases at UIUC during Fall 2020 and Spring 2021, as shown in Fig 3A, where several mild spikes were observed. There is no estimated effective reproduction number from 2020-08-18 to 2020-08-24 because we use data from the seven-day window between 2020-08-18 and 2020-08-25 to estimate the effective reproduction number for 2020-08-25. We do not have sufficient data to estimate the effective reproduction number prior to 2020-08-25.