Novel coronavirus 2019-nCoV: early estimation of epidemiological parameters and epidemic predictions

Jonathan M Read; Jessica RE Bridgen; Derek AT Cummings; Antonia Ho; Chris P Jewell

We estimated that the average ascertainment rate in Wuhan between 1 and 22 January was 5.0% (95%CI, 3.6-7.4), reflecting the difficulty in identifying cases of a novel pathogen. Given the generally good accessibility to healthcare in China, this suggests that the majority of infections may be of mild illness and insufficiently serious for individuals to seek treatment. However, it is worth noting that a number of identified cases have died (Centre for Disease Control and Prevention 2020) and that the true case fatality rate has yet to be estimated accurately. Also, asymptomatic infection has been reported for 2019-nCoV (Chan et al., 2020) . We also estimated the size of the epidemic in Wuhan at the time of the market closure (1 January) to be 15 individuals (95%CI, 5-37). Our estimates of epidemiological parameters are sensitive to our assumption regarding the length of the latent period; see Figure 2 . Early epidemiological investigations suggest a duration between 3 to 6 days (Chan et al., 2020) , Should the latent period be longer than the 4 days we assume, our 0 estimates would be higher and the estimated ascertainment rate slightly lower; see Figure 2 .