Epidemiologic Characteristics of a COVID-19 Outbreak Caused by Religious Activities in Daegu, Korea.

Objectives: A coronavirus disease (COVID-19) outbreak triggered by religious activities occurred in Daegu, South Korea in February 2020. This outbreak spread rapidly to the community through high-risk groups. This study describes the characteristics of the COVID-19 cases based on S religious group membership and summarizes Daegu City's processes and responses to control the outbreak.
Methods: Epidemiologic characteristics of confirmed cases were obtained through basic and in-depth epidemiological surveys. General characteristics, asymptomatic proportion, case-fatality rates, and time-to-event within each group were presented after stratifying confirmed cases according to S religious group membership.
Results: Overall, 7,008 COVID-19 cases were confirmed in Daegu from February 18 to June 30, 2020, and 61.5% (n=4,309) were S religious group members. Compared with non-members, members had a higher proportion of women (p<0.001), younger age (p<0.001), and lower disease prevalence. Asymptomatic cases included 38.4% of members and 23.7% of non-members (p<0.001) at the time of the investigation. The case-fatality rate of non-members aged ≥60 years was significantly higher than that of members (p<0.001). Compared with non-members, the durations of symptom onset to diagnosis (p<0.001) and diagnosis to admission (p<0.001) of members were longer, whereas the duration of admission to discharge (p<0.001) was shorter.
Conclusion: The epidemiologic features of S religious group members, including asymptomatic proportion, case-fatality rate, and time-to-event, differed from non-members. Daegu City prevented further spread of COVID-19 through immediate isolation and active screening tests of all S religious group members.