Estimating clinical severity of COVID-19 from the transmission dynamics in Wuhan, China

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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 approximator ¹ 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).

Abstract

An estimation of the clinical severity of COVID-19, based on the data available so far, can help to inform the public health response during the ongoing SARS-CoV-2 pandemic.

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Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travellers from Wuhan, China, 20–28 January 2020

Jantien Backer, Don Klinkenberg, Jacco Wallinga (2020)

A novel coronavirus (2019-nCoV) is causing an outbreak of viral pneumonia that started in Wuhan, China. Using the travel history and symptom onset of 88 confirmed cases that were detected outside Wuhan in the early outbreak phase, we estimate the mean incubation period to be 6.4 days (95% credible interval: 5.6–7.7), ranging from 2.1 to 11.1 days (2.5th to 97.5th percentile). These values should help inform 2019-nCoV case definitions and appropriate quarantine durations.

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Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong

Christl Donnelly, Azra C. Ghani, Gabriel Leung … (2003)

Summary Background Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong. Methods We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients’age and the time from onset to admission. Findings After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% Cl 5.2–7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8–16.8) for patients younger than 60 years and 43.3% (35.2–52.4) for patients aged 60 years or older assuming a parametric γ distribution. A non-parametric method yielded estimates of 6.8% (4.0–9.6) and 55.0% (45.3–64.7), respectively. Case clusters have played an important part in the course of the epidemic. Interpretation Patients’age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine. Published online May 7, 2003 http://image.thelancet.com/extras/03art4453web.pdf

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The epidemiology of severe acute respiratory syndrome in the 2003 Hong Kong epidemic: an analysis of all 1755 patients.

Gabriel Leung, Anthony J. Hedley, Lai-Ming Ho … (2004)

As yet, no one has written a comprehensive epidemiologic account of a severe acute respiratory syndrome (SARS) outbreak from an affected country. To provide a comprehensive epidemiologic account of a SARS outbreak from an affected territory. Epidemiologic analysis. The 2003 Hong Kong SARS outbreak. All 1755 cases and 302 deaths. Sociodemographic characteristics; infection clusters by time, occupation, setting, and workplace; and geospatial relationships were determined. The mean and variance in the time from infection to onset (incubation period) were estimated in a small group of patients with known exposure. The mean and variance in time from onset to admission, from admission to discharge, or from admission to death were calculated. Logistic regression was used to identify important predictors of case fatality. 49.3% of patients were infected in clinics, hospitals, or elderly or nursing homes, and the Amoy Gardens cluster accounted for 18.8% of cases. The ratio of women to men among infected individuals was 5:4. Health care workers accounted for 23.1% of all reported cases. The estimated mean incubation period was 4.6 days (95% CI, 3.8 to 5.8 days). Mean time from symptom onset to hospitalization varied between 2 and 8 days, decreasing over the course of the epidemic. Mean time from onset to death was 23.7 days (CI, 22.0 to 25.3 days), and mean time from onset to discharge was 26.5 days (CI, 25.8 to 27.2 days). Increasing age, male sex, atypical presenting symptoms, presence of comorbid conditions, and high lactate dehydrogenase level on admission were associated with a greater risk for death. Estimates of the incubation period relied on statistical assumptions because few patients had known exposure times. Temporal changes in case management as the epidemic progressed, unavailable treatment information, and several potentially important factors that could not be thoroughly analyzed because of the limited sample size complicate interpretation of factors related to case fatality. This analysis of the complete data on the 2003 SARS epidemic in Hong Kong has revealed key epidemiologic features of the epidemic as it evolved.

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Author and article information

Contributors

Joseph T. Wu:

ORCID: http://orcid.org/0000-0002-3155-5987

joewu@hku.hk

Journal

Journal ID (nlm-ta): Nat Med

Journal ID (iso-abbrev): Nat. Med

Title: Nature Medicine

Publisher: Nature Publishing Group US (New York )

ISSN (Print): 1078-8956

ISSN (Electronic): 1546-170X

Publication date (Electronic): 19 March 2020

Pages: 1-5

Affiliations

[1 ]ISNI 0000000121742757, GRID grid.194645.b, WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, LKS Faculty of Medicine, , The University of Hong Kong, ; Hong Kong SAR, China

[2 ]ISNI 000000041936754X, GRID grid.38142.3c, Center for Communicable Disease Dynamics, Department of Epidemiology, , Harvard T.H. Chan School of Public Health, ; Boston, MA USA

Author information

Joseph T. Wu http://orcid.org/0000-0002-3155-5987

Benjamin J. Cowling http://orcid.org/0000-0002-6297-7154

Article

Publisher ID: 822

DOI: 10.1038/s41591-020-0822-7

PMC ID: 7094929

PubMed ID: 32284616

SO-VID: 4f8e3cfe-9d7a-42d6-9127-bcb3038d64fc

License:

This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

History

Date received : 13 February 2020

Date accepted : 9 March 2020

Funding

Funded by: FundRef https://doi.org/10.13039/501100005847, Food and Health Bureau of the Government of the Hong Kong Special Administrative Region | Health and Medical Research Fund (HMRF);

Funded by: Fellowship Foundation Ramon Areces

Funded by: FundRef https://doi.org/10.13039/100000057, U.S. Department of Health & Human Services | NIH | National Institute of General Medical Sciences (NIGMS);

Award ID: U54GM088558

Award Recipient : Mary Bushman Nishant Kishore Rene Niehus Pablo M. de Salazar Marc Lipsitch

Estimating clinical severity of COVID-19 from the transmission dynamics in Wuhan, China

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Novel Coronavirus Disease COVID-19

Most cited references 14

Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travellers from Wuhan, China, 20–28 January 2020

Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong

The epidemiology of severe acute respiratory syndrome in the 2003 Hong Kong epidemic: an analysis of all 1755 patients.

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