Types of COVID-19 clusters and their relationship with social distancing in the Seoul metropolitan area, South Korea

Abstract

Background Complete contact tracing of COVID-19 patients in Korea allows a unique opportunity to investigate cluster characteristics. This study aimed to investigate all the reported COVID-19 clusters in Seoul Metropolitan area from January 23 to September 24, 2020. Methods Publicly available COVID-19 data was collected from the Seoul Metropolitan city and Gyeonggi Province. Community clusters with ≥ 5 cases were characterized by size and duration and then categorized using K-means clustering, and the correlation between the types of clusters and the level of social distancing was investigated. Results A total of 134 clusters including 4,033 cases were identified. The clusters were categorized into small (Type I, II), medium (type III), and large (type IV) clusters. With the same number of daily confirmed cases, cases were composed of different types of clusters by different periods of time. Raising social distancing was related with shifting types of clusters from large to small sized clusters. Conclusions Classification of clusters may provide opportunities to better portray the pattern of COVID-19 outbreaks and implement more effective strategies. Social distancing administered by the government may be effective in suppressing large clusters but may not be effective in controlling small and sporadic clusters.

Analysis of Superspreading Potential from Transmission Clusters of COVID-19 in South Korea

“…The size of the majority of clusters in churches, workplaces and schools ranged between 20 and 40. It can be interpreted that clusters may have formed in large numbers and over longer periods of time, but they were effectively managed owing to better control measures, resulting in a reduced number of cases [ 17 ]. Although the government implemented nonpharmaceutical interventions including social distancing in public facilities, transmission is still steadily occurring in the above cluster categories.…”

“…In the present study, a cluster is defined as a group of at least 20 cases of COVID-19, including one or more primary cases. A previous study carried out cluster-induced transmission analysis with clusters with more than five cases for the first and the second waves of COVID-19 in the Seoul metropolitan area [ 17 ]. As the third wave of COVID-19 in South Korea began in November 2020 [ 3 ], our time window of interest spanned from the first wave to the early third wave.…”

Characteristics of transmission routes of COVID-19 cluster infections in Gangwon Province, Korea

“…The in-depth epidemiological investigation verified where the patient stayed and with whom they had contact in the period between 2 days before the symptom onset date and the COVID-19 test date. If the patient did not manifest symptoms of COVID-19, the tracing was conducted from 2 days before the COVID-19 test [15]. Contacts of confirmed patients were instructed to undergo COVID-19 testing and were subject to selfisolation, active surveillance, or simple testing depending on the level of contact.…”

Implementation of Environmental Sanitation and Disinfection in Hospitals to Reduce the Spread of Covid19: A Literature Review

“…This has driven a new cluster classification which now includes a group that has >5 cases (16)(17). In South Korea, where 134 clusters with 4,033 cases were identified, the clusters are categorized into: small clusters (type I and II), medium clusters (type III) and large clusters (type IV) (18). Clusters that are susceptible to Covid19 infection are clusters in hospitals.…”