Estimating the Prevalence of Asymptomatic COVID-19 Cases and Their Contribution in Transmission - Using Henan Province, China, as an Example

Chunyu Li; Yuchen Zhu; Chang Qi; Lili Liu; Dandan Zhang; Xu Wang; Kaili She; Yan Jia; Tingxuan Liu; Daihai He; Momiao Xiong; Xiujun Li

doi:10.3389/fmed.2021.591372

Estimating the Prevalence of Asymptomatic COVID-19 Cases and Their Contribution in Transmission - Using Henan Province, China, as an Example

Front Med (Lausanne). 2021 Jun 23:8:591372. doi: 10.3389/fmed.2021.591372. eCollection 2021.

Authors

Chunyu Li¹, Yuchen Zhu¹, Chang Qi¹, Lili Liu¹, Dandan Zhang¹, Xu Wang¹, Kaili She¹, Yan Jia¹, Tingxuan Liu¹, Daihai He², Momiao Xiong³, Xiujun Li¹

Affiliations

¹ Department of Biostatistics, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China.
² Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China.
³ Department of Biostatistics and Data Science, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX, United States.

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, R _t . 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 R ₀ = 2.73, and R _t 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: COVID-19; asymptomatic cases; infectious dynamic model; prevention and control measures; the effective reproductive number.