But for any single exposure, you have to factor in a) the odds the
oral partner has
oral herpes, b) if so, whether or not s/he is having an outbreak at the time of exposure, c) if no outbreak, whether asymptomatic viral shedding might be present, d) whether the genital partner already has HSV-1, which would make him or her immune (or at least highly resistant) to a new infection, and e) perhaps other factors, like the duration and vigor of exposure, perhaps circumcision status, and maybe still