Herpes is about the only thing I would worry about with regulator sharing, and that only if the person had an active outbreak in proximity to the regulator. I looked for information on herpes virus survival; it's very brief on dry surfaces and in chlorinated water, like pools or hot tubs. It's several hours in a moist environment. I could not find anything on the efficacy of simple rinsing (as would occur while a reg was being passed from one diver to the other) as a mechanism for getting rid of the virus. I think it's reasonable to be reluctant to do gas-sharing drills with someone with an active cold sore.
Can we get back to the original topic now, please?
Can we get back to the original topic now, please?