Risk assessment of novel coronavirus COVID-19 outbreaks outside China

Peter Boldog; Tamas Tekeli; Zsolt Vizi; Attila Denes; Ferenc Bartha; Gergely Rost

Since the first case outside Hubei was reported on 19 January [5] , for the initialization of the model we could assume that number of infected individuals on 23 January outside Hubei was equal to the number of cumulative cases outside Hubei up to that day. To calibrate the model, we estimated the number of cases from 24 January till 31 January outside Hubei based on case exportations, using the methodology of [15] , assuming that exportations after 24 January were only from outside Hubei. Based on the maximal likelihood of case numbers that produce the observed number of exportations using EpiRisk [32] , we estimate that the reported confirmed cases represent only 6.3% of the total cases for the regions outside Hubei (other estimates for ascertainment rate were: 5.1% [22] , 10% in [38] , and 9.2% (95% confidence interval: 5.0, 20.0) [39] ), see the inset in Figure 1 . The initial values for the exposed compartments in the SEIR model were selected such that the model output was consistent with the estimated case numbers outside Hubei between 24 January and 31 January. Solving the compartmental model, we obtained final epidemic sizes for various reproduction numbers and control efforts (see Figure 1 ), providing upper bounds for the cumulative number of cases C outside Hubei.