Risk Assessment of Importation and Local Transmission of COVID-19 in South Korea: Statistical Modeling Approach

Abstract

Background Despite recent achievements in vaccines, antiviral drugs, and medical infrastructure, the emergence of COVID-19 has posed a serious threat to humans worldwide. Most countries are well connected on a global scale, making it nearly impossible to implement perfect and prompt mitigation strategies for infectious disease outbreaks. In particular, due to the explosive growth of international travel, the complex network of human mobility enabled the rapid spread of COVID-19 globally. Objective South Korea was one of the earliest countries to be affected by COVID-19. In the absence of vaccines and treatments, South Korea has implemented and maintained stringent interventions, such as large-scale epidemiological investigations, rapid diagnosis, social distancing, and prompt clinical classification of severely ill patients with appropriate medical measures. In particular, South Korea has implemented effective airport screenings and quarantine measures. In this study, we aimed to assess the country-specific importation risk of COVID-19 and investigate its impact on the local transmission of COVID-19. Methods The country-specific importation risk of COVID-19 in South Korea was assessed. We investigated the relationships between country-specific imported cases, passenger numbers, and the severity of country-specific COVID-19 prevalence from January to October 2020. We assessed the country-specific risk by incorporating country-specific information. A renewal mathematical model was employed, considering both imported and local cases of COVID-19 in South Korea. Furthermore, we estimated the basic and effective reproduction numbers. Results The risk of importation from China was highest between January and February 2020, while that from North America (the United States and Canada) was high from April to October 2020. The R0 was estimated at 1.87 (95% CI 1.47-2.34), using the rate of α=0.07 for secondary transmission caused by imported cases. The Rt was estimated in South Korea and in both Seoul and Gyeonggi. Conclusions A statistical model accounting for imported and locally transmitted cases was employed to estimate R0 and Rt. Our results indicated that the prompt implementation of airport screening measures (contact tracing with case isolation and quarantine) successfully reduced local transmission caused by imported cases despite passengers arriving from high-risk countries throughout the year. Moreover, various mitigation interventions, including social distancing and travel restrictions within South Korea, have been effectively implemented to reduce the spread of local cases in South Korea.

Factors Associated with Mental Health among International Students during the COVID-19 Pandemic in South Korea

“…In this study, data were collected in December 2020 and, in the studies cited above, data were collected between April and June. The first half of 2020 was a period in which the fatality rate of COVID-19 had greatly increased [25], and the second half of 2020 was a period in South Korea in which the spread of infection was being mitigated with solid infection control strategies [26]. This could explain the lower prevalence rates of anxiety and depression among international students compared to those of previous studies.…”

Epidemiological Characteristics and Core Containment Measures of Imported COVID-19 Cases from Abroad in Early Phase in Guangdong, China

“…Moreover, the experiences of Singapore, South Korea, and Taiwan and Hong Kong, China in early imported cases from abroad have shown that timely inbound temperature and symptom screening, isolation, close contact tracing, under strict enforcement of these measures and aggressive border control measures are effective in preventing COVID-19 community transmission. 5 , 15 , 16 …”

“…Moreover, the experiences of Singapore, South Korea, and Taiwan and Hong Kong, China in early imported cases from abroad have shown that timely inbound temperature and symptom screening, isolation, close contact tracing, under strict enforcement of these measures and aggressive border control measures are effective in preventing COVID-19 community transmission. 5,15,16 The SARS-CoV-2 positive nucleic acid test is a crucial standard for the detection and confirmation of COVID-19 cases. 10 Furthermore, a study showed that rapid and accurate testing of clinical samples dictates the effective response.…”

Discovering spatiotemporal patterns of COVID-19 pandemic in South Korea

“…These include recent emerging infectious diseases; novel H1N1 influenza, SARS-CoV-1, Zika, MERS-CoV, and SARS-CoV-2 13 . Recent emerging infectious diseases tend to spread all over the world within a shorter time scale due to dramatic increases in international flights and human mobility 13 , 14 . There has been much research on spatial–temporal patterns of COVID-19 using various modeling approaches 9 , 10 , 15 , 16 .…”