Effective containment explains sub-exponential growth in confirmed cases of recent COVID-19 outbreak in Mainland China

Benjamin F Maier; Dirk Brockmann

We find that for a wide range of model parameters, the case count is well reproduced by the model. The model reproduces the scaling law t µ as observed in the data for a significant period of time before saturating to a finite level. Remarkably, the model is able to reproduce both growth behaviors observed in the data: The model predicts the expected initial growth of case numbers in Hubei Province followed by an algebraic growth episode for ≈ 11 days until the saturation sets in, a consequence of the decay of unidentified infected individuals after a peak time around Feb. 7th (see Fig. 2A) . Furthermore, the model also captures the immediate sub-exponential growth observed in the remaining most affected provinces (Fig. 2B-C) . Again, saturation is induced by a decay of unidentified infecteds after peaks that occur several days before peak time Province N/10 6 Q P I 0 /X 0 R 0,eff in Hubei, ranging from Jan. 31st to Feb. 5th. For all provinces, following their respective peaks the number of unidentified infecteds I(t) decays over a time period that is longer than the reported estimation of maximum incubation period of 14 days [7, 13] . It is important to note that due to the uncertainty in the population size, the numerical value of unidentified infecteds is sensitive to parameter variations-the general shape of I(t), however, is robust for a wide choice of parameters, as discussed in App. A. Parameter choices for best fits were a fixed basic reproduction number of R 0,free = 6.2 (note that this reproduction number corresponds to an unconstrained epidemic) and a fixed mean infection duration of T I = 8 d consistent with previous reports concerning the incubation period of COVID-19 [7, 13] . The remaining fit parameters are shown in Tab. I. For these values, the effective basic reproduction number is found to range between 1.7 ≤ R 0,eff ≤ 3.3 for the discussed provinces, consistent with estimates found in previous early assessment studies [6, 7, 18, 19] .