This study estimates the clinical severity of COVID-19 in Wuhan, China, using public and published data. As of 29 February 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) was estimated at 1.4% (0.9–2.1%), which is lower than the crude case fatality risk (4.5%) and the approximator of deaths/deaths + recoveries (11%). The risk of symptomatic infection increased with age, with those aged below 30 and above 59 years being more likely to die after developing symptoms. The study used an age-structured transmission model to infer clinical severity estimates, incorporating data on confirmed cases, deaths, and travel-related infections. The model estimated the basic reproductive number (R0) as 1.94 (1.83–2.06), with a mean serial interval of 7.0 days and a mean time from onset to death of 20 days. The epidemic doubling time was 5.2 days before public health interventions reduced transmissibility by 48%. The study found that the sCFR was highest in the oldest age group, with the risk of symptomatic infection increasing with age. The estimated sCFR was 1.4% (0.9–2.1%), with those aged <30 years and >59 years being 0.16 and 2.0 times more susceptible to symptomatic infection, respectively. The study also noted that the true case fatality risk may be lower than the crude case fatality risk due to under-ascertainment of cases in Wuhan. The study compared the clinical severity of COVID-19 with other pathogens, finding that it is less severe than SARS and MERS, but more severe than the 1918 influenza pandemic. The study highlights the importance of estimating clinical severity for public health decision-making, particularly in the context of a novel pathogen with a high basic reproductive number. The study also discusses the challenges of estimating clinical severity in an overwhelmed healthcare system and the need for accurate case fatality risk estimates to guide public health interventions. The study concludes that the clinical severity of COVID-19 is lower than previously estimated, and that public health interventions are necessary to control its spread.This study estimates the clinical severity of COVID-19 in Wuhan, China, using public and published data. As of 29 February 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) was estimated at 1.4% (0.9–2.1%), which is lower than the crude case fatality risk (4.5%) and the approximator of deaths/deaths + recoveries (11%). The risk of symptomatic infection increased with age, with those aged below 30 and above 59 years being more likely to die after developing symptoms. The study used an age-structured transmission model to infer clinical severity estimates, incorporating data on confirmed cases, deaths, and travel-related infections. The model estimated the basic reproductive number (R0) as 1.94 (1.83–2.06), with a mean serial interval of 7.0 days and a mean time from onset to death of 20 days. The epidemic doubling time was 5.2 days before public health interventions reduced transmissibility by 48%. The study found that the sCFR was highest in the oldest age group, with the risk of symptomatic infection increasing with age. The estimated sCFR was 1.4% (0.9–2.1%), with those aged <30 years and >59 years being 0.16 and 2.0 times more susceptible to symptomatic infection, respectively. The study also noted that the true case fatality risk may be lower than the crude case fatality risk due to under-ascertainment of cases in Wuhan. The study compared the clinical severity of COVID-19 with other pathogens, finding that it is less severe than SARS and MERS, but more severe than the 1918 influenza pandemic. The study highlights the importance of estimating clinical severity for public health decision-making, particularly in the context of a novel pathogen with a high basic reproductive number. The study also discusses the challenges of estimating clinical severity in an overwhelmed healthcare system and the need for accurate case fatality risk estimates to guide public health interventions. The study concludes that the clinical severity of COVID-19 is lower than previously estimated, and that public health interventions are necessary to control its spread.