Estimation of the Excess COVID-19 Cases in Seoul, South Korea by the Students Arriving from China

Abstract

Background: In March 2020, overall, 37,000 international students from China, a country at risk of the 2019-novel coronavirus (COVID-19) infection has arrived in Seoul, South Korea. Individuals from the country at risk of COVID-19 infection have been included in the Korean home-quarantine program, but the efficacy of the program is uncertain. Methods: To estimate the possible number of infected individuals within the large influx of international students from China, we used a deterministic compartmental model for epidemic and performed a simulation-based search of different rates of compliance with home-quarantine. Results: Under the home-quarantine program, the number of the infected individuals would reach 40-72 from 12 March-24 March with the arrival of 0.2% of pre-infectious individuals. Furthermore, the number of isolated individuals would peak at 40-64 from 13 March-27 March in Seoul, South Korea. Our findings indicated when incoming international students showed strict compliance with quarantine, epidemics by the international student from China were less likely to occur in Seoul, South Korea. Conclusions: To mitigate possible epidemics, additional efforts to improve the compliance of home-quarantine of the individuals from countries with the virus risk are warranted along with other containment policies.

Keywords: COVID-19; Korea; compliance; coronavirus; quarantine; simulation.

Figure 1

Graphical illustration of deterministic SEIR compartment model with quarantine. The population is divided into five classes: susceptible, exposed (infected with the virus but not infectious yet), infectious (symptomatic only), and recover. Exposed individuals are quarantined on contact tracing with a fraction of the compliance rate.

Figure 2

Estimated daily number of individuals with infection in Seoul, South Korea under different scenarios regarding the proportion of pre-infectious individuals: 0.1% (A), 0.2% (B), and 1% (C), based on different compliance rates with home-quarantine (gray: baseline, black: 70%, blue: 80%, red: 90%, green: 100%). Shaded gray bars represent the period of arrival of the international students from China, the country with the risk of 2019 novel coronavirus on February 2020.

Figure 3

Estimated daily number of isolated individuals in Seoul, South Korea, under different scenarios regarding the proportion of pre-infectious individuals: 0.1% (A), 0.2% (B), or 1% (C) based on different compliance rates with home-quarantine (gray: baseline, black: 70%, blue: 80%, red: 90%, green: 100%). Shaded gray bars represent the period of arrival of the international students from China, the country with the risk of 2019 novel coronavirus on February 2020.