Quorum sensing is a regulatory mechanism that enables bacteria to make collective decisions with respect to the expression of a specific set of viral instructions which can be related to virulence factors.
This is why outdoor gatherings and outdoor activities in general are safer than indoor gatherings.
We live with countless billions of bacteria on this planet that do the bidding of viral instructions where indoor gatherings like churches, schools, bars, care facilities and theaters make quorum much easier to be achieved.
There is just no good reason to put yourself in a place where quorum could be achieved. And being outside is a good place to avoid that. Or at least keep some windows open and fresh air blowing through.