kissing, passing joints around, mate gourd... effects?

Factual Questions
1

I remember when I used to be a big pot smoker back in the day, passing joints and pipes from mouth to mouth. I imagine that in terms of transfer/exchange of substances and bacteria, it must be right up there with kissing. Has anyone ever done a study or calculated the results of this mass exchange of bodily fluids in terms of health, immune system… the common cold? The effects could be positive or negative, actually.

I recall when I hung out in Paraguay that more or less the same phenomena was occurring with the passing of the mate gourd and the straw from mouth to mouth.

It’s like a mass bacteria exchange among the population. So, good, bad, or ugly? Is there any straight dope about this? Or will this be relegated to the great debates forum?

2

I don’t have an answer, but it made me think of how kava is traditionally prepared–it’s chewed and then made into a drink (not just for the chewer). I know I just read about another drink whose main ingredient was chewed as part of the preparation. So I’m wondering the same thing about these as bardos is in his OP.

3

It’s just the hippie pot-smokers’ version of the now-discredited Chicken Pox Party.