Would you want to know if they'd kissed someone else?Watch this thread
Actually, I've just been in this situation - in reverse. A girl kissed me a couple of nights ago and right away I texted my girlfriend to inform her. Naturally one of her first questions was, "how long did it take you to tell me?" She was glad that I didn't hesitate to let her know what had happened.
It wouldn't matter to me any more than a hug or handshake.
Assuming that the individual was not a known criminal or obvious walking public health disaster.
It will just cause ongoing dramatic events.