Well, beyond taking their temperatures as they check in, or spraying them with disinfectant, there’s not a lot you can do. I’m joking of course. What I should have said is that there’s not a lot you can do as long as you allow short-term lets.
I wonder what the DA of your block says regarding holiday lets. If it says your block is residential only, the best thing you can do is change your by-laws to enforce the terms of your DA, and put the holiday flats back into the residential pool.