Early Trend of Imported COVID-19 Cases in South Korea

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 20th, a total of 171 imported cases have been officially reported in South Korea as of March 23rd 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.