... is, or is not, Covid still a public health issue?
If it is then people have the right to know what risk they are being exposed to. Especially the elderly or those with health conditions that compromise them.
If I belonged to that choir and was told I didn't have the right to know who was infected, I simply would not turn up for rehearsals, of for any events.
What is the point of being told that some are affected if you don't know whether or not you will be sitting close to them. Distancing and masks only offer a certain amount of protection, and you can't sing with a mask on. In fact, singing has been categorised as one of the higher risk activities.
I'm not sure why people are being so precious about hiding the fact they have the disease - no-one is going to lay any blame on them for having contracted it.
If you had a stinking cold, you would probably think twice about passing it on to others... well, I certainly would, and would just stay away for a few days... why is this so different?