> These studies typically can't be done for ethics reasons today - it wouldn't meet ethics standards to deliberately infect someone with something harmful. You

> These studies typically can't be done for ethics reasons today - it wouldn't meet ethics standards to deliberately infect someone with something harmful. You don't need to deliberately infect people. Right now hospital air is not being filtered anywhere as far as I Understand. You could start installing air filters in hospitals and have some other hospitals as a control group. You closely monitor how much air is filtered, which filters are in use, and leave some hospitals unfiltered. You might find out that filtering works. Or only certain filters work. Or that filtering spreads disease through air movement. Or a mix of these, maybe disease x goes down while y goes up.