What proportion of COVID-19 cases lead to severe outcomes?

Bottom Line:

The case fatality risk of symptomatic COVID-19 was 1.4% in Wuhan, China. The risk of having symptomatic infection or death increased with age, particularly those above 59 years. This information can help health providers ensure we are prepared and have enough supplies through the peak and duration of this pandemic.


Wu, J.T. et al. Estimating clinical severity of COVID-19 from the transmission dynamics in Wuhan, China. Nature Medicine (2020). https://doi.org/10.1038/s41591-020-0822-7

Date Published:

19 March 2020


Mathematical modelling was used to analyse data on patients with COVID-19 in Wuhan, China and estimate of the clinical severity (the proportion of severe outcomes and the delay between symptoms onset and death) of this illness. The authors found that the overall symptomatic case fatality risk of COVID-19 in Wuhan is about 1.4%, 95% CI [0.9-2.1%], and increases with greater age. Those above 59 years of age were 5.1 (95% CI: 4.2-6.1) times more likely to die after developing symptoms than those aged 30-59 years. COVID-19 had a lower symptomatic case fatality rate (number of deaths compared to number of patients with a positive diagnosis) than SARS and MERS, as well as two past influenza pandemics in 1918 and 2009. However, COVID-19 is likely to infect more individuals because of presymptomatic transmission and evidence of extensive community spread in several countries. Ultimately, an understanding of the clinical severity of COVID-19 is important to guide clinical decision-making (e.g. clinical suspicion for COVID-19 in an undiagnosed patient) and the public health response (e.g. obtaining personal protective equipment supplies). These results may not apply to those outside the original epicentre because their healthcare systems may have added experience gained from managing initial patients and availability of newer and more effective treatment options. However, the authors can still make a call to “flatten out” the epidemic curve so that there may sufficient time for clinical expertise and treatment options to develop.

Summary by: Mike Ge