That could explain why such a high % got sick. Would have to assume a few had covid but were asymptomatic. Would be hard to believe just one person could infect that many - Aerosolization or not. But I guess it is possible.
We know in the hospital world NIPPV (CPAP/BiPAP) and even HF nasal cannula is no longer recommended as bridging therapy to help avoid intubation unless there is a specific indication - also due to aerosolization and increased risk to nursing/healthcare poviders.