Risk assessment of novel coronavirus COVID-19 outbreaks outside China

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

Based on the previous estimates from the literature (see Table 1 ), we chose an incubation period α −1 = 5.1 days [30] , basic reproduction number R 0 = 2.6 (2.1-3.1) with the corresponding infectious period γ −1 = 3.3 (1.7-5.6) days [19] . To predict the final number of cases outside Hubei, we assume a gradually increasing control u from zero until a saturation point, and define t * the time when the eventual control u max is achieved. The sooner this happens, the more successful the control is. Using the control term u(t) = min{u max t/t * , u max }, disease control is reached at t = t * (1 − 1/R 0 )/u max . For the calculations we choose u max = 0.8, noting that such a drop in transmission has been observed for SARS, where the reproduction number was largely reduced by subsequent interventions [35] . With our baseline R 0 = 2.6, disease control R(t) < 1 is achieved when u(t) > 0.615, meaning that more than 61.5% of potential transmissions are prevented, which occurs at time t = 0.77t * .