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Title: Estimating the prevalence of asymptomatic COVID-19 cases and their contribution in transmission - using Henan Province, China, as an example
Authors: Li, C
Zhu, Y
Qi, C
Liu, L
Zhang, D
Wang, X
She, K
Jia, Y
Liu, T
He, D 
Xiong, M
Li, X
Issue Date: Jun-2021
Source: Frontiers in medicine, June 2021, v. 8, 591372
Abstract: Background: Novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), is now sweeping across the world. A substantial proportion of infections only lead to mild symptoms or are asymptomatic, but the proportion and infectivity of asymptomatic infections remains unknown. In this paper, we proposed a model to estimate the proportion and infectivity of asymptomatic cases, using COVID-19 in Henan Province, China, as an example.
Methods: We extended the conventional susceptible-exposed-infectious-recovered model by including asymptomatic, unconfirmed symptomatic, and quarantined cases. Based on this model, we used daily reported COVID-19 cases from January 21 to February 26, 2020, in Henan Province to estimate the proportion and infectivity of asymptomatic cases, as well as the change of effective reproductive number, Rt.
Results: The proportion of asymptomatic cases among COVID-19 infected individuals was 42% and the infectivity was 10% that of symptomatic ones. The basic reproductive number R0 = 2.73, and Rt dropped below 1 on January 31 under a series of measures.
Conclusion: The spread of the COVID-19 epidemic was rapid in the early stage, with a large number of asymptomatic infected individuals having relatively low infectivity. However, it was quickly brought under control with national measures.
Keywords: Asymptomatic cases
Infectious dynamic model
Prevention and control measures
The effective reproductive number
Publisher: Frontiers Research Foundation
Journal: Frontiers in medicine 
EISSN: 2296-858X
DOI: 10.3389/fmed.2021.591372
Rights: © 2021 Li, Zhu, Qi, Liu, Zhang, Wang, She, Jia, Liu, He, Xiong and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) ( The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
The following publication Li C, Zhu Y, Qi C, Liu L, Zhang D, Wang X, She K, Jia Y, Liu T, He D, Xiong M and Li X (2021) Estimating the Prevalence of Asymptomatic COVID-19 Cases and Their Contribution in Transmission - Using Henan Province, China, as an Example. Front. Med. 8:591372 is available at
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