Evaluation of COVID-19 epidemic outbreak caused by temporal contact-increase in South Korea

Abstract

Objectives: On March 15, 2020, 61.3% of the confirmed cases of COVID-19 infection in South Korea are associated with the worship service that was organized on February 9 in the Shincheonji Church of Jesus in Daegu. We aim to evaluate the effects of mass infection in South Korea and assess the preventive control intervention.

Method: Using openly available data of daily cumulative confirmed cases and deaths, the basic and effective reproduction numbers was estimated using a modified susceptible-exposed-infected-recovered-type epidemic model.

Results: The basic reproduction number was estimated to be R₀=1.77. The effective reproduction number increased approximately 20 times after the mass infections from the 31 st patient, which was confirmed on February 9 in the Shincheonji Church of Jesus, Daegu. However, the effective reproduction number decreased to less than unity after February 28 owing to the implementation of high-level preventive control interventions in South Korea, coupled with voluntary prevention actions by citizens.

Conclusion: Preventive action and control intervention were successfully established in South Korea.

Keywords: 2019 novel coronavirus disease; Effective reproduction number; Epidemic model; SARS-CoV-2.

Figure 1

COVID-19 outbreak size in South Korea from January 20 to March 15 versus time. The blue bar graph represents the cumulated confirmed cases and dotted line the daily confirmed cases.

Figure 2

Fitting the 100-chain model to confirmed cases and deaths data. The black squared dots in both panels represent the data of the cumulative numbers of confirmed cases and deaths, respectively. The best-fit curves are shown as red solid line in both the panels. The estimated values of the parameters are β₀=0.59, β₁=11.73, κ=0.353, and δ=0.018.