Real-time tentative assessment of the epidemiological characteristics of novel coronavirus infections in Wuhan, China, as at 22 January 2020

Wu, Peng; Hao, Xinxin; Lau, Eric H Y; Wong, Jessica Y; Leung, Kathy S M; Wu, Joseph T; Cowling, Benjamin J; Leung, Gabriel M

It is challenging to judge severity from the information available to date. We estimated the risk of death among hospitalised cases of around 14% (Figure 2 ). For both SARS-CoV and MERS-CoV infections, the risk of severe disease increases substantially with age and with the presence of underlying conditions [23] [24] [25] . One other caveat with estimating severity is that there can be long delays between hospitalisation and death for infections that are ultimately fatal. For SARS in Hong Kong, the average time from illness to death for fatal cases was 24 days [26] . This means that early estimates of the case fatality risk that ignore the potential outcomes of cases still in hospital are typically underestimates of the final severity profile [27] . We accounted for that by only including cases that either died or recovered in our estimate of the hospital fatality risk. Given that the cases reported outside Wuhan have mostly not been severe, it would be reasonable to infer that there might be a large number of undetected relatively mild infections in Wuhan and that the infection fatality risk is below 1% or even below 0.1%.