The study, coming as states begin to reopen, highlights how a single workshop among 27 dance fitness instructors in South Korea was responsible for more than 100 coronavirus cases spread across 12 fitness facilities in the city of Cheonan.
Eight instructors at the Feb. 15 meeting had the coronavirus but they hadn’t known yet — they were asymptomatic.
Over the course of the next 24 days, by March 9, the virus spread to across fitness classes to 112 participants, according to the research team at Dankook University Hospital.
High-octane workouts in confined spaces can be ripe environments for the spread of the virus, the researchers said.
“Characteristics that might have led to transmission from the instructors in Cheonan include large class sizes, small spaces, and intensity of the workouts,” wrote the scientists in their research letter published by the CDC late last week. “The moist, warm atmosphere in a sports facility coupled with turbulent air flow generated by intense physical exercise can cause more dense transmission of isolated droplets.”
Each dance class linked to transmission had between five and 22 students. About half of the 112 cases were transmitted from instructors to students, the contact tracers found.
In all, 54 students out of the 217 attending the classes who were exposed to the virus came ended up tested positive, an infection rate of 26 percent.
The rest of the cases stemmed from the sick students who then passed the virus to family, friends and coworkers.The infected students didn’t start displaying symptoms until about 3.5 days after attending the class on average, the researchers found.
The study found that several lower-intensity workouts weren’t as effective in transferring the virus.
One of the instructors from the initial workshop also taught yoga and pilates classes for groups of seven to eight people. But researchers found that none of the students in those classes ended up catching the bug.
“We hypothesize that the lower intensity of Pilates and yoga did not cause the same transmission effects as those of the more intense fitness dance classes,” the researchers wrote.