At what point during sex does an std get passed from one to another?

Fluids/ shedding: Usually when fluids are exchanged. But witih herpes if could just be related to shedding.

Anything touching: Contact is what passes infection of most types. In the case of sex, it's everything: kissing, rubbing, oral sex, fingers on or in, and penetration of any type. Viruses, bacteria, and other stds can be carried in blood, saliva, vaginal secretions, semen, and other moist or seemingly dry surfaces. These days, it's almost like you need to exchange std panel reports before you decide to commit!