Vidcast:  https://youtu.be/MP1WdHpiQoQ   Eighty-five percent of singers caught CoVid from a single infected person during one 2.5 hour rehearsal.  Environmental engineers now analyze this Washington State case report..   During the March 10th rehearsal in question, the precautions taken only included use of hand sanitizer and no physical contacts such as hugging or handshaking.  Face masks were not used.  Attendees rapidly became sick over the 5 days following the rehearsal.  Studying the group placement chart, spread of virus appeared random.  Air was recirculated through a standard commercial filter.   This is a wake up call.  Re-opening cannot be business as usual and be safe.  MDW: mask, distance, wash.   https://www.medrxiv.org/content/10.1101/2020.06.15.20132027v2.full.pdf   #covid #airborne #masks