Someone should look at Sterilray and Ushio 222nm KrCl excimer lamps. Light at that frequency is extremely effective at destroying viruses but probably does not cause much skin cancer or eye damage like other UV because it is absorbed so fast it doesn't make it through the dead layer of skin etc. There are at least some studies but no FDA approval or mass production. If they work these might make a big difference in transmission in public spaces, especially via surfaces.