why would you want to go and infect all the audience who may have paid good money to see you?

As an organiser I would rather have the artist get in touch with me, if they have an illness that can be passed on to the audience. I would rather they cancel and re book at another time. I would then find somebody to do that night, even at the last minute.

Yes the audience might be disapointed, but at least your bug wouldn't be passed on to them.