Risk assessment of novel coronavirus COVID-19 outbreaks outside China

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

This is an extension of a standard SEIR model assuming gamma-distributed incubation and infectious periods, with the Erlang parameters n = 2, m = 3 (following the SARS-study [37] ). Note that the choice of n = 2 is also consistent with the estimates summarized in Table 1 . Given that disease fatalities do not have significant effect on the total population, we ignored them in the transmission model to ease the calculations (i.e., µ = 0 was used). In this model, the basic reproduction number is R 0 = β/γ, the incubation period is α −1 and the infectious period is γ −1 . The model is used to describe the disease dynamics in China outside Hubei province after 23 January. We assume that at time t after 23 January, an increasing control function u(t) represents the fraction of the transmissions that are prevented, thus the effective reproduction number becomes R(t) = (1 − u(t))R 0 S(t)/N.