Abstract
As of 29 February 2020 there were 79,394 confirmed cases and 2,838 deaths from COVID-19 in mainland China. Of these, 48,557 cases and 2,169 deaths occurred in the epicenter, Wuhan. A key public health priority during the emergence of a novel pathogen is estimating clinical severity, which requires properly adjusting for the case ascertainment rate and the delay between symptoms onset and death. Using public and published information, we estimate that the overall symptomatic case fatality risk (the probability of dying after developing symptoms) of COVID-19 in Wuhan was 1.4% (0.9–2.1%), which is substantially lower than both the corresponding crude or naïve confirmed case fatality risk (2,169/48,557 = 4.5%) and the approximator1 of deaths/deaths + recoveries (2,169/2,169 + 17,572 = 11%) as of 29 February 2020. Compared to those aged 30–59 years, those aged below 30 and above 59 years were 0.6 (0.3–1.1) and 5.1 (4.2–6.1) times more likely to die after developing symptoms. The risk of symptomatic infection increased with age (for example, at ~4% per year among adults aged 30–60 years).
Highlights
On 9 January 2020, the novel coronavirus SARS-CoV-2 was officially identified as the cause of the COVID-19 outbreak in Wuhan, China
At the population level, determining the shape and size of the ‘clinical iceberg’[2,3], both above and below the observed threshold, is key to understanding the transmission dynamics and interpreting epidemic trajectories
For a completely novel pathogen, especially one with a high basic reproductive number relative to other recently emergent and seasonal directly transmissible respiratory pathogens[4], assuming homogeneous mixing and mass action dynamics, the majority of the population will be infected eventually unless drastic public health interventions are applied over prolonged periods and/or vaccines become available sufficiently quickly
Summary
Market (which was postulated to be the index zoonotic source of the COVID-19 epidemic) between 10 December 2019 and 3 January 2020 (Fig. 1 and Supplementary Table 1)7. 2. 6. The cumulative number of deaths among confirmed cases of COVID-19 infection in Wuhan as of 25 February 20209 (Supplementary Table 6). Because (1) the majority of COVID-19 infections do not cause severe disease[8] and (2) hospitals in Wuhan have been overwhelmed, presumably having led to prioritized admission of more serious cases, the sCFR will be substantially lower than the HFR. These do not enter our estimates of sCFR, but if such asymptomatic or clinically very mild cases existed and were not detected, the infection fatality risk would be lower than sCFR Further clarifying this requires new data sources that are not yet available, including agestratified serologic studies. Received: 13 February 2020; Accepted: 9 March 2020; Published online: 19 March 2020
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