The Skagit Valley Chorale in Washington State gathered for their normal practice on March 10th. The area they are located in, Skagit County didn’t have any coronavirus cases yet. The choir director reportedly decided to hold practice, but with some precautions in place. Seats were further apart than usual, hand sanitizer was given out at the door and members were asked not to touch each other. No one reportedly appeared sick, but yet now weeks later we know at least one person in the room had coronavirus and spread it to dozens of other choir members. Two of those members are dead.

The Los Angeles Times interviewed eight people who were at the rehearsal, they all “said that nobody there was coughing or sneezing or appeared ill.” So what is behind the rapid spread? The newspaper adds this:

 Jamie Lloyd-Smith, a UCLA infectious disease researcher, said it’s possible that the forceful breathing action of singing dispersed viral particles in the church room that were widely inhaled.

“One could imagine that really trying to project your voice would also project more droplets and aerosols,” he said.

With three-quarters of the choir members testing positive for the virus or showing symptoms of infection, the outbreak would be considered a “super-spreading event,” he said.

Watch more from the NBC affiliate in Seattle above.