key: cord-1023322-qjwn1h2g
authors: Choe, Young June
title: Coronavirus disease-19: Summary of 2,370 Contact Investigations of the First 30 Cases in the Republic of Korea
date: 2020-03-18
journal: nan
DOI: 10.1101/2020.03.15.20036350
sha: 7f7d59ece5faa33e6c08c50f0c4546f471cd5b0c
doc_id: 1023322
cord_uid: qjwn1h2g

Between January 24 and March 10, of a total of 2,370 individuals who had contacted the first 30 cases of COVID19, 13 were found to have COVID19, resulting secondary attack rate of 0.55% (95% CI 0.31 to 0.96). Of 119 household contacts, 9 had infections resulting secondary attack rate of 7.56 (95% CI 3.73 to 14.26).

Since the importation of coronavirus disease 2019 in the Republic of Korea, the first 30 confirmed cases were reported as of February 17th, 2020. The epidemiological and clinical characteristics of 28 cases of those were analyzed in previous report (1) .

Tracing of contacts of cases is essential for containing COVID-19 within the community. In Korea, an established system exists using public health centers to conduct epidemiological investigation and early quarantine/isolation of suspected case, thus interrupting the line of transmission. This approach has been particularly successful in containing the COVID-19 in early phase of outbreak.

Here, we describe the summary of 2,370 contact investigations of the first 30 cases of coronavirus disease-19 (COVID-19) in Korea. The study includes a secondary attack rates among different age groups and mode of transmission.

Demographic, epidemiological, and early clinical information were retrieved from COVID-19 reporting and surveillance data from Korea Centers for Disease Control and Prevention (KCDC). As in previous report, patient age was provided on the date of diagnosis, and key indicators were identified by an epidemiological investigator who participated in the field investigation and the epidemiological investigation team (1). It must be noted that the data presented in this study may change depending on the results of further epidemiological investigation.

Initial working definition for 'close contact (or high risk exposure)' was defined as being within approximately 2 meters of a COVID-19 case; and definition for 'daily contact (or All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted March 18, 2020. . https://doi.org/10.1101/2020.03.15.20036350 doi: medRxiv preprint low risk exposure)' was defined as having proximity of a person with confirmed COVID-19 case, without having had close contact. The classification was then repealed and was integrated into 'contact (regardless of level of exposure)'. All asymptomatic contacts were mandated to stay self-quarantine for 14 days and were put under active surveillance by public health workers who called twice a day to check presence of fever or respiratory symptoms. Smartphone-based 'self-assessment app' was introduced as an additional tool to track the symptoms.

Between January 24 and March 10, of a total of 2,370 individuals who had contacted the first 30 cases of COVID-19, 12 were found to have COVID-19, resulting secondary attack rate of 0.55% (95% CI 0.31 -0.96) ( (Table 2 ).

Tracing of 2,370 contacts of the first 30 COVID-19 cases in Korea indicate that the risk of symptomatic transmission among contacts was low at 0.55% (95% CI 0.31 -0.96). However, the findings also suggested that the transmission of COVID-19 was significant among household contacts, which is in line with other reports. In the earlier reports, familial clusters had been reported and was there were question on whether household transmission could be a major driver in spread of outbreak in the community (2, 3). Of the first 262 COVID-19 cases All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in in Beijing, China, 133 (50.8%) were family cluster cases (4). In the US, an active symptom monitoring was performed for 445 close contacts of the 12 cases with travel-related COVID-19, resulting a symptomatic secondary attack rate of 0.45% (95% CI, 0.12 -1.6) among all contacts, and 10.5% (95% CI, 2.9 -31.4) among household members (5).

This study suggest that contact tracing was critical for containing the COVID-19 outbreak in the early phase in Korea. Contact tracing rely on other concurrent aspects of the COVID-19 containment strategies such as investigating, classifying, tracking, and managing contacts by identifying the patient's route. A mathematical model suggested highly effective contact tracing and case isolation was enough to control a new outbreak of COVID-19 in most scenarios (6). In Korea, various measures such as tracking the history of clinic visits, GPS of the cell phones, credit card transaction log, and CCTV had been utilized to complete the contact tracing of COVID-19 cases (7).

There are certain limitations that should be considered. First, this is a summary of the first 30 cases of COVID-19 in Korea, when containing of the cases and contacts was the mainstay of control strategy. Following the increase of cases after case number 31, the strategy has shifted from containment to mitigation, which is now applied in many parts of the world. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in 

Early Epidemiological and Clinical Characteristics of 28 Cases of Coronavirus Disease in South Korea