I hesitated on buying a UV flashlight thinking it may be a waste of money. Today I went to Harbor Freight and bought one. It seems that Yes indeed...they do work on viruses. It doesn't kill Covid-19, it makes it unable to reproduce.
https://phys.org/news/2020-06-coronavirus-handheld-ultraviolet-device-feasible.html
Unfortunately, today CNN reported this. So, there will be either a shortage on them or they will be very expensive.