Evolving Transmission Network Dynamics of COVID-19 Cluster Infections in South Korea: a descriptive study.

Abstract Background Extensive contact tracing and testing in South Korea allows us to investigate the transmission dynamics of the COVID-19 into diverse local communities. Objective Understand the critical aspects of transmission dynamics in a different age, sex, and clusters with various activities. Methods We conducted a retrospective observational study with 3,127 confirmed cases’ contact tracing data from the Center for Disease and Prevention (CDC) of South Korea. We investigated network property concerning infected persons’ demographics and different infection clusters. Findings Overall, women had higher centrality scores than men after week four, when the confirmed cases rapidly increased. Older adults have higher centrality than young/middle-aged adults after week 9. In the infection clusters, young/middle-aged adults’ infection clusters (such as religious gatherings and gym facilities) have higher average path lengths and diameter than older adult’s nursing home infection clusters. Interpretation Some women had higher reproduction numbers and bridged successive transmission than men when the confirmed cases rapidly increased. Similarly, some older adults (who were not residents of nursing homes) had higher reproduction numbers and bridged successive transmission than young/middle-aged adults after the peak has passed. The young/middle-aged adults’ religious gatherings and group workout have caused long successive transmissions. In contrast, the older adults’ nursing homes were a small world where the transmissions within a few steps can reach out to many persons. Funding UT Startup award, UT STARs award, and Cancer Prevention Research in Texas, and National Institute of General Medical Sciences Research in context Evidence before this study: On May 1, 2020, PubMed query (“COVID-19” OR “SARS-nCoV-2” OR “novel coronavirus” OR “nCoV”) AND (“transmission network” OR “transmission dynamics” OR “transmission pattern” OR “centrality”) AND (“cluster” OR “community”) yield eight peer-reviewed papers. These papers have provided an evolving epidemiology and transmission dynamics via estimated reproduction number. However, most of them have focused on the entire system in one location and there was no comparison between transmission dynamics of different clusters. Added value of this study: This study, to the best of our knowledge, is the first to compare the transmission dynamics of different cluster infections. We present the transmission dynamic with varying levels of granularity: entire country vs cluster infections as a longitudinal view. From the whole country-level analysis, we found that females have higher centrality (degree or betweenness) than males. From the cluster infection view, we found that young/middle-aged adults’ infection clusters (such as religious gatherings and gym facilities) have higher average path lengths and diameter than older adult’s nursing home infection clusters. Implications of all the available evidence: This study sheds light on different transmission dynamics concerning demographics (age and sex) and diverse behavior in cluster infections. These findings are essential for planning tailored policies to diverse communities. Our analysis code is publicly available to adapt to newly reported cases.