It may be a long time before it is safe to sing together.
Here are summary notes from a webinar held yesterday, hosted by a group of choral organizations and medical specialists.
https://docs.google.com/document/d/10zLES6zlmtqwh3hj_n73zYpsFVWgfW3HSYGE7NsR3Mw/
The source webinar is here, but they had technical problems. The description is worth reading for the background of the speakers.
https://youtu.be/DFl3GsVzj6Q