CHICAGO (WLS) -- The Centers for Disease Control and Prevention released a case report Wednesday involving a high "attack rate" at a Chicago gym, where infrequent mask wearing was reported.
In August of last year, during one week of a high-intensity fitness class, 55 out of 81 attendees developed COVID. Some took classes on the same day or after receiving a positive test result.
Twenty-two (40%) of people with COVID-19 attended on or after the day symptoms began, health officials said. Most attendees (76%) wore masks infrequently, including people with (84%) and without (60%) COVID-19, the CDC said.
The report reinforces public health guidance that mask wearing and staying home when ill are critical for reducing the spread of the virus.
The CDC said gyms should require masks during exercise, decrease class sizes, require physical distancing and improve ventilation to avoid incidents like this. Gyms should also encourage attendees to isolate after symptoms appear or after receiving a positive COVID-19 test and to quarantine after a potential exposure and while awaiting test results.
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CrossTown Fitness has three locations in Chicago. At their West Loop gym they have safety measures in place including frequent deep cleanings, temperature checks and reduced class sizes.
"Classes are at 15 people max," said Christopher Burt with CrossTown Fitness. "Before COVID, you would have seen 30 people in that studio."
Health experts are aware that increased heavy breathing enables coronavirus spread and outbreaks linked to indoor activities have been reported.
Clients of the gym who take their high intensity classes said wearing a mask makes it harder to breathe, but they will adhere to rules to stay healthy.
"I still want to stay in shape, so you have to adapt to the times and wear a mask, and I think it's gonna be the norm for the near future," said David Litvinov, gym goer.
"For people who are really into fitness, we are willing to do whatever it takes to be safe and still get our workouts in," said Trinidad Perez, fitness buff.
Exercising outdoors or virtually could further reduce the risk of the virus being spread.
The CDC did not specify what gym was studied.
The video in the player above is from an earlier report.
CDC report shows 55 of 81 Chicago gym-goers, infrequent mask-wearers contracted COVID-19
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