Minnesota Department of Health has been producing some really great coronavirus epidemiology work. This case study looked at gym transmission at two gyms in the state that had large outbreaks.
Gyms in this study were high transmission environments as many of the exposed persons, including employees, did not isolate and quarantine as they should. Rather alarmingly most days of the week had at least one employee and a large number of gym attendees that were infectious.
They found that a lot of gym visitors and gym employees didn't tell the truth about being at the gym when interviewed. They cross-referenced state test data with the gym visitor sheet data to see what the actual behavior of the members was like. Many of those that were infected attended the gym after symptom onset and after testing. Those that were supposed to be quarantining due to home positive cases were still attending gyms.
Those of you who attend gyms that are not yet vaccinated may want to avoid them and wear masks while at them.
One of the downsides of US contact tracing this pandemic has been a lot of non-compliance. Other countries like South Korea and Vietnam have augmented their tracing with tracking data and other passive information such that they aren't so reliant on case interviews to track spread.
Regardless of how folks felt about the lockdowns, I would have thought “quarantine if you actually have the disease” would have been less debatable...