https://astralcodexten.substack.com/p/book-review-from-oversight-to-overkill

I. Risks May Include AIDS, Smallpox, And Death

Dr. Rob Knight studies how skin bacteria jump from person to person. In one 2009 study, meant to simulate human contact, he used a Q-tip to cotton swab first one subject's mouth (or skin), then another's, to see how many bacteria traveled over. On the consent forms, he said risks were near zero - it was the equivalent of kissing another person's hand.