During a March 10 choir practice in Skagit County, WA, a single person—possibly a "superemitter"—likely infected 52 / 60 people in attendance (87%).

No reported physical contact & few opportunities for fomites. Most likely cause: droplets & aerosols https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm

Contrary to some earlier reports, the singers were not several feet apart. They sat within 6 to 10 inches of each other. There were also snacks available, though many reported not eating them. Each returned their own chair to the racks, but they gathered in a group to do so.

Given the lack of direct physical contact and shared objects, this was most likely transmission via respiratory droplets. Earlier research has shown that the act of singing increases production of aerosols. Even talking and breathing produce droplets.

Several lines of evidence indicate that for many people prolonged activities in crowded indoor spaces pose the greatest risk of infection with SARS-CoV-2. This should be foremost in our minds as we learn to adapt.