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

Abstract

Background: In February 2020, a coronavirus disease 2019 (COVID-19) outbreak was reported in fitness centers in Cheonan, Korea. Methods: 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. Results: 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 timedependent 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. Conclusion: 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.

Household Transmission of SARS-CoV-2

“…We identified 54 relevant published studies that reported household secondary transmission, with 77 758 participants (eTable 1 in the Supplement ). 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 A total of 16 of 54 studies (29.6%) were at high risk of bias, 27 (50.0%) were moderate, and 11 (20.4%) were low (eTable 2 in the Supplement ). Lower quality was attributed to studies with 1 or fewer test per contact (35 studies [64.8%]), small sample sizes (31 [57.4%]), a...…”

“…Figure 1 summarizes secondary attack rates for 44 studies 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 28 , 29 , 30 , 32 , 33 , 34 , 35 , 36 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 59 , 61 , 62 , 63 , 65 , 66 , 67 , 69 , 70 of household contacts and 10 of family contacts. 26 , 31 , 37 , 45 , 58 , 60 , 65 , 68 , 71 , 72 Estimated mean secondary attack rate for household contacts was 16.4% (95% CI, 13.4%-19.6%) and family contacts was 17.4% (95% CI, 12.7%-22.5%).…”

“…To study the transmissibility of asymptomatic SARS-CoV-2 index cases, eFigure 8 in the Supplement summarizes 27 studies 19 , 20 , 21 , 23 , 24 , 25 , 26 , 30 , 32 , 33 , 34 , 44 , 45 , 47 , 50 , 52 , 53 , 54 , 56 , 59 , 60 , 61 , 63 , 64 , 68 , 69 , 72 reporting household secondary attack rates from symptomatic index cases and 4 studies 26 , 43 , 44 , 52 from asymptomatic or presymptomatic index cases. Estimated mean household secondary attack rate from symptomatic index cases (18.0%; 95% CI, 14.2%-22.1%) was significantly higher than from asymptomatic or presymptomatic index cases (0.7%; 95% CI, 0%-4.9%; P < .001), although there were few studies in the latter group.…”

Effects of chronic exposure to ambient air pollutants on COVID-19 morbidity and mortality - A lesson from OECD countries

“…In addition to the well-known negative health outcomes of chronic PM 2.5 exposure [ 1 , 4 , 5 ], several recent studies postulated that PM aerosols can also serve as a vector transporting bacteria and viruses through airborne diffusion, allowing them to penetrate deeply into the lungs and surpass the multilayer barriers of the respiratory system, thus enhancing SARS-CoV-2 virus transmission mechanism [ 13 , 14 ]. Such airborne transmission route for COVID-19 was suggested as a possible reason for mass indoor infections in restaurants, buses and fitness centers and in some cases via ventilation systems [ [26] , [27] , [28] ]. Such a route was also recognized by the CDC in 2020 under special circumstances such as: 1.…”

Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant

“…[ 14 ]; who also concluded that “nearly all SSEs [super spreading events] in the database took place indoors.” [ 15 ] identified 318 outbreaks each with a minimum of 3 cases, comprising a total of 1245 confirmed cases in 120 prefectural cities in non-Hubei provinces, China, and found that none occurred in outdoor settings. High attack rates of COVID-19 have also been found in choir rehearsal [ 7 , 16 ], homeless shelters [ [17] , [18] , [19] ]; nightclubs [ 20 ]; Fitness centers [ 21 , 22 ] and meat processing plants [ 23 ]. Although airborne transmission has been suspected in many of these outbreaks, ventilation rates were not measured in the infection venues.…”