A tiny, tiny fraction. And this would benefit us for way more than just Covid.
UV bulbs are expensive (and invisible unless you get to poke around a buildings mechanical room.), they need to be replaced typically ~annually (they won't be). If they get dust on them, they don't work as well. Etc. etc.
And here's the issue: To actually deal with high concentration infectious aerosols you need to get that air out of the room ASAP. (i.e. negative pressure rooms) If you can sterilize the return air that's great, but frankly I suspect dilution and air movement is going to be the dominant effect in reducing infection chains.
I was in a gym that required everyone to wear a mask (yes, while working out / on a treadmill / etc), but all the large windows were shut, and nobody seemed to care or notice. No staff, no patrons, nobody. So I walked around and opened all the windows. And this wasn't March 2020. This was like end of 2021.
I'm not claiming to be some pandemic savant, nor getting into a mask debate, but what shocked me was the "group psychosis" on masking at the expense of proven and incredibly easy mitigation efforts like opening windows!
What is needed is effective prophylactics (beyond mRNA vaccines) and effective treatment. But the effort spent on that is, sadly, minimal.