Effect of Non-lockdown Social Distancing and Testing-Contact Tracing During a COVID-19 Outbreak in Daegu, South Korea, February to April 2020: A Modeling Study. (September 2021)

• Record Type: Journal Article
• Authors: Chen, Yi-Hsuan; Fang, Chi-Tai; Huang, Yu-Ling
• Is Part Of: International journal of infectious diseases. Volume 110(2021)
• Page Start: 213
• Page End: 221
• Publication Date: 2021-09
• Subjects: Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2021.07.058
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: In early 2020, the first large COVID-19 outbreak outside China occurred in Daegu The SARS-CoV-2 strain involved in Daegu outbreak has an R0 of 3.6 (range: 2.3 to 5.6) The Daegu outbreak was successfully controlled without restricting movement. A combination of social distancing and testing-contact tracing is highly effective. Both interventions must be enacted for successful control of an COVID-19 outbreak Abstract: Objective: In Spring 2020, South Korea applied non-lockdown social distancing (avoiding mass gathering and non-essential social engagement, without restricting the movement of people who were not patients or contacts), testing-and-isolation (testing), and tracing-and-quarantine the contacts (contact tracing) to successfully control the first large-scale COVID-19 outbreak outside China. However, the relative contributions of these two interventions remain uncertain. Methods: We constructed an SEIR model of SARS-CoV-2 transmission (disproportionately through superspreading events) and fit the model to outbreak data in Daegu, South Korea, from February to April 2020. We assessed the effect of non-lockdown social distancing (population-wide control measures) and/or testing-contact tracing (individual-specific control measures), alone or combined, in terms of the basic reproductive number (R0) and the trajectory of the epidemic. Results: The point estimate for baseline R0 is 3.6 (sensitivity analyses range: 2.3 to 5.6). Combined interventions of non-lockdown social distancing and testing-contact tracing can suppress R0 to less than one and rapidly contain the epidemic, even under the worst scenario with a high baseline R0 of 5.6. In contrast, either intervention alone will fail to suppress R0. Non-lockdown social distancing alone just postpones the peak of the epidemic, while testing-contact tracing alone only flattens the curve but does not contain the outbreak. Conclusions: To successfully control a large-scale COVID-19 outbreak, both non-lockdown social distancing and testing-contact tracing must be implemented. The two interventions are synergistic.