J Korean Med Sci.  2020 Aug;35(31):e288. 10.3346/jkms.2020.35.e288.

Epidemiological Characteristics of COVID-19 Outbreak at Fitness Centers in Cheonan, Korea

  • 1Department of Preventive Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 2Epidemiology & Case Management Team, COVID-19 National Emergency Response Center, Korea Centers for Disease Control and Prevention, Cheongju, Korea
  • 3Chungnam Center for Infectious Diseases Control and Prevention, Hongseong, Korea
  • 4Seosan Public Health Center, Seosan, Korea
  • 5Department of Preventive Medicine, College of Medicine, Dankook University, Cheonan, Korea


In February 2020, a coronavirus disease 2019 (COVID-19) outbreak was reported in fitness centers in Cheonan, Korea.
From February 24 to March 13, an epidemiological investigation was conducted on the fitness center outbreak. All those who were screened were tested for severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) using real-time reverse transcriptase polymerase chain reaction. Contacts were traced and self-isolated for 14 days. We determined the epidemiological characteristics of confirmed cases of SARS-CoV-2 infection, and estimated the time-dependent reproduction number to assess the transmission dynamics of the infection.
A total of 116 cases were confirmed, and 1,687 contacts were traced. The source cases were 8 Zumba instructors who led aerobics classes in 10 fitness centers, and had the largest average number of contacts. A total of 57 Zumba class participants, 37 of their family members, and 14 other contacts were confirmed as cases. The attack rate was 7.3%. The contacts at Zumba classes and homes had a higher attack rate than other contacts. The mean serial interval (± standard deviation) were estimated to be 5.2 (± 3.8) days. The time-dependent reproduction number was estimated to be 6.1 at the beginning of the outbreak, but it dropped to less than 1, 2 days after the epidemiological investigation was launched.
The results suggest that the COVID-19 outbreak was effectively contained with rigorous contact tracing, isolating, and testing in combination with social distancing without a lock-down.


Coronavirus; Disease Outbreak; Epidemiology; Basic Reproduction Number; Fitness Centers
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