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Risk Assessment of Importation and Local Transmission of COVID-19 in South Korea: Statistical Modeling Approach.
Lee, Hyojung; Kim, Yeahwon; Kim, Eunsu; Lee, Sunmi.
  • Lee H; National Institute for Mathematical Sciences, Daejeon, Republic of Korea.
  • Kim Y; Kyung Hee University, Yongin-si, Republic of Korea.
  • Kim E; Kyung Hee University, Yongin-si, Republic of Korea.
  • Lee S; Kyung Hee University, Yongin-si, Republic of Korea.
JMIR Public Health Surveill ; 7(6): e26784, 2021 06 01.
Article in English | MEDLINE | ID: covidwho-2197902
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.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: Communicable Diseases, Imported / COVID-19 Type of study: Diagnostic study / Observational study / Prognostic study Topics: Vaccines Limits: Humans Country/Region as subject: Asia Language: English Journal: JMIR Public Health Surveill Year: 2021 Document Type: Article

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Communicable Diseases, Imported / COVID-19 Type of study: Diagnostic study / Observational study / Prognostic study Topics: Vaccines Limits: Humans Country/Region as subject: Asia Language: English Journal: JMIR Public Health Surveill Year: 2021 Document Type: Article