While a Dr's note may be the preferred action for many from the local sawbones, most rv types likely (and especially the retired folks) are not worried about that. Being forgiven a day away from the office is much less important than being free of the virus.
Maybe I am being overtly wrong, but, avoiding the virus altogether, is more important than attending a minor gathering of forgotten Jimmy Buffet, (or, insert group here) fans, other non necessary group fans or wannabee types here.
I just don't see the Dr's note helping RV'ers. We tend to be a splinter group that the rest of society tends to forget.
Embrace your solitude.