Role of Asymptomatic COVID-19 Cases in Viral Transmisssion: Findings from a Hierarchical Community Contact Network Model

Abstract

Background: As part of on-going efforts to contain the 2019 novel coronavirus disease (COVID-19) pandemic, population-wide screening is being performed, identifying an increasing number of asymptomatic cases. Understanding the role of asymptomatic patients in the transmission system is essential to infection control. However, optimal approach to risk assessment and management of asymptomatic cases remains unclear. Methods: This study involved a SEINRHD epidemic propagation model, constructed based on epidemiological characteristics of COVID-19 in China, accounting for the heterogeneity of social network in this population. Computational experiments were performed to assess epidemic control measures for asymptomatic cases on three dimensions. Impact of asymptomatic cases on epidemic propagation was examined based on the effective reproduction number, abnormally high transmission events, type of transmission, and transmission tree structure.Findings: Management of asymptomatic cases can help flatten the infection curve. Specifically, asymptomatic case tracking appears to have significant effect on epidemic progression, whereby tracking 75% of asymptomatic cases corresponds to an overall reduction in new cases of 34·3% (compared to tracking no asymptomatic cases). When timely measures are taken for symptomatic cases and the intensity is strong enough, the overall epidemic is not sensitive to the implementation time of the measures for asymptomatic cases. Finally, regardless of population-wide measures, family transmission is higher than other types of transmission, accounting for an estimated 50% of all new cases.Interpretations: These findings can help assess interventions aimed at asymptomatic case management during the COVID-19 pandemic, helping to control disease spread. In addition, these findings might also help identify the type of transmission and abnormally high transmission events that may exist during the epidemic.Funding: This study was funded by National Natural Science Foundation of China (Nos. 72042018, 91546112, 71621002) and Beijing Municipal Natural Science Foundation (No. L192012).Declaration of Interests: All authors declare no competing interests.