key: cord-0804898-wpdzdxoi
authors: nan
title: Early Trend of Imported COVID-19 Cases in South Korea
date: 2020-06-03
journal: Osong Public Health Res Perspect
DOI: 10.24171/j.phrp.2020.11.3.01
sha: 5ea55773a1e4d812f061bef7bbfa3c9e7de6863e
doc_id: 804898
cord_uid: wpdzdxoi

This study aimed to observe the initial trend of imported COVID-19 cases in South Korea since the beginning of the outbreak. All imported cases were classified into 5 regions (China, Asia, Europe, Africa, and America) according to travel history and potential exposure to the COVID-19. The list of countries for which confirmed cases had a travel history (single visit, multiple visits) and presented, were used to estimate the potential “exposure countries” of confirmed cases. For better understanding of the overall imported cases, time differences (day) among 3 major steps (symptom onset, entry to South Korea, laboratory confirmation) were measured based on available data. From the first importation of a COVID-19 case on January 20(th), a total of 171 imported cases have been officially reported in South Korea as of March 23(rd) 2020. The overall trend of importation has significantly changed during this period. Importation of confirmed cases were initially from China, and subsequently from other Asian countries. After that, importation from Europe rapidly increased, with importation from America also increasing. One hundred fifteen (81%) were confirmed within 7 days of symptom onset. One Hundred forty three (84.1%) imported cases were confirmed within a week after entry into South Korea. One hundred seven imported cases (75.9%) developed symptoms within 5 days before or after, entry to South Korea. Streamlined processes of detection, subsequent testing, isolation, and treatment by public health authority, was key in minimizing the risk of secondary transmission.

14 days before the entry to South Korea, were collected for descriptive analysis. To observe the initial trend of imported COVID-19 cases, all imported cases were classified into 5 regions (China, Asia (excluding China), Europe, Africa, and America) according to travel history, and potential exposure to COVID-19.

The list of countries for which confirmed cases had visited were classified into 2 categories (single visit, and multiple visits), and presented to estimate the potential exposure countries of confirmed cases. For better understanding of the overall imported cases, time differences (days) among 3 major steps (symptom onset date, entry date to South Korea, laboratory confirmation date) were measured based on the available data.

From the first importation of a COVID-19 case on January 20 th , a total of 171 imported cases have been officially reported in Korea as of March 23rd. Out of 171 total imported cases, 96 (56.1%) were male, and 75 (43.9%) were female. Reporting locations of imported cases, Incheon airport quarantine station reported the most cases (38.6%), followed by Seoul (26.9%) and Gyeonggi (18.7%). Daegu only reported 2 imported cases despite there being a major cluster of infections in the city (Table 1) . Gimhae airport quarantine station reported 1 imported case. The main age groups of imported cases were people in their 20s (43.9% of total cases) and 30's [24.0% of total cases (Table 2) ].

The overall trend of importation has significantly changed during the study period ( Figure 1 Among 142 imported cases whose symptom onset date was available, a time difference between symptom onset and laboratory confirmation ranged from 0 to 22 days ( Figure 2 ).

There were 115 (81%) imported cases that were confirmed positive within 7 days after symptom onset, and 42 cases (29.6%) were confirmed just 1 day after symptom onset. Only 5 cases (3.5%) were confirmed after 14 days of symptom onset.

One hundred seventy imported cases had clear information on their entry date to South Korea. The time difference between entry and confirmation is presented in Figure 3 . More than half of imported cases (56.5%) were confirmed within 2 days after entry. One hundred forty three (84.1%) of imported cases were confirmed within a week after entry to South Korea. Data for some imported cases of travelers who had traveled to more than 1 country before traveling to South Korea, did not allow for a country to be specified. Symptom onset date of confirmed cases were based on preliminary epidemiological investigations and can be updated after further investigations.

Lastly, this study period only covered the initial stage of the COVID-19 pandemic and the overall pattern of import from various countries will change by the end of the pandemic. 

There are no conflicts of interest to declare.

KCDC Risk Assessments on the Initial Phase of the COVID-19 Outbreak in Korea

Serial interval of novel coronavirus (COVID-19) infections

World Health Organization

COVID-19) Situation Report-63

Press Release: The updates on COVID-19 in Korea as of 24 March