The study estimates the clinical severity of COVID-19 in Wuhan, China, by analyzing transmission dynamics and case ascertainment rates. As of February 29, 2020, there were 79,394 confirmed cases and 2,838 deaths in mainland China, with 48,557 cases and 2,169 deaths in Wuhan. The overall symptomatic case fatality risk (sCFR) in Wuhan was estimated to be 1.4% (0.9–2.1%), significantly lower than the crude CFR of 4.5% and the approximator of 11%. The risk of symptomatic infection increased with age, with those aged below 30 and above 59 years being 0.6 and 5.1 times more likely to die after developing symptoms, respectively. The study used a range of data sources, including confirmed case numbers, travel data, and death reports, to infer the epidemiologic parameters of COVID-19 in Wuhan. The basic reproductive number was estimated to be 1.94, and the mean serial interval was 7.0 days. The study highlights the importance of understanding the clinical iceberg and the impact of under-ascertainment on severity estimates. The findings suggest that COVID-19 transmission is difficult to control, and public health interventions are crucial to reducing the peak demand on healthcare services.The study estimates the clinical severity of COVID-19 in Wuhan, China, by analyzing transmission dynamics and case ascertainment rates. As of February 29, 2020, there were 79,394 confirmed cases and 2,838 deaths in mainland China, with 48,557 cases and 2,169 deaths in Wuhan. The overall symptomatic case fatality risk (sCFR) in Wuhan was estimated to be 1.4% (0.9–2.1%), significantly lower than the crude CFR of 4.5% and the approximator of 11%. The risk of symptomatic infection increased with age, with those aged below 30 and above 59 years being 0.6 and 5.1 times more likely to die after developing symptoms, respectively. The study used a range of data sources, including confirmed case numbers, travel data, and death reports, to infer the epidemiologic parameters of COVID-19 in Wuhan. The basic reproductive number was estimated to be 1.94, and the mean serial interval was 7.0 days. The study highlights the importance of understanding the clinical iceberg and the impact of under-ascertainment on severity estimates. The findings suggest that COVID-19 transmission is difficult to control, and public health interventions are crucial to reducing the peak demand on healthcare services.