A new CDC report published today has detailed how 55 of 81 attendees at an exercise facility in Chicago were diagnosed with Covid-19 during a one week period between August and September 2020.
The facility held four to eight daily classes at <25% capacity with 10-15 people per class and mask use, symptom screenings and temperature checks were required on entry. Patrons brought their own mats, weights and were distanced by 6ft or more. However, they were allowed to remove their masks during exercise and ultimately over two-thirds of the patrons ended up with Covid-19. Two of the attendees with Covid-19 visited an emergency department and one person ended up being hospitalized for 8 days.
Fifty eight attendees agreed to be interviewed by public health authorities investigating the outbreak, with 76% of them reporting infrequent mask use during the class. 86% of people who were Covid-19 positive reported not wearing a mask during class, with 60% of people who did not get Covid-19 reporting the same. Attendees went to an average of 5 exercises classes during the outbreak week.
An analysis of the interviews and timing of those who tested Covid-19 positive revealed that 43 people (78%) of them attended at least one exercise class during their estimated infectious periods. Some of them were asymptomatic and likely were not aware that they had Covid-19, but twenty two of the attendees with Covid-19 attended classes either on, or after the day of symptom onset, with three patrons who attended on the same day, or after they received a positive Covid-19 test result. After receiving notification of a Covid-19 case in a patron, the exercise facility closed and informed all other patrons of a possible exposure.
The Chicago Department of Public Health, who led the investigation of the outbreak, concluded that the high proportion of attendees with Covid-19 who participated in classes while symptomatic, or asymptomatic and infectious, was largely responsible for the high number of infections linked to the facility. Infrequent mask use during high-intensity exercise which creates high volumes of respiratory droplets was also cited as contributing to transmission.
Because the outbreak involved people who attended several exercise classes throughout the week, the investigation was unable to conclude whether one, or several people started off this super spreader chain of events. The report re-emphasizes what should really be common sense, that nobody should be socializing with others in any setting if they have symptoms associated with Covid-19 and/or are waiting for a test result.
The report further concludes that the outbreak occurred despite the use of some Covid-19 mitigation methods and recommends that all people in exercise facilities should wear a mask at all times, including during high-intensity activities even if they are >6ft apart. Improvements in ventilation should also be considered, with classes being held outdoors or virtually as the most preferred options.
The Covid-19 risk posed by gyms and other group fitness settings has been a controversial topic with group fitness classes repeatedly being linked to huge outbreaks, such as one in Hamilton, Canada which led to over seventy cases of Covid-19.
It is increasingly obvious that >6ft distancing alone is completely inadequate as a method to reduce transmission when unmasked people are exercising in enclosed environments with no to little ventilation. The rise of new coronavirus variants which are more transmissible, such as the B.1.1.7 “UK variant” may also increase risk of transmission in these environments.
So as gyms and fitness facilities re-open across the U.S., patrons should ask themselves a few questions to help them make their decision as to whether to attend. These include whether they and other patrons must be masked while exercising, if there is adequate ventilation and whether they trust all of the staff and patrons not to come to the facility if they are sick.