Semen on, not in, anus

[pantaloneypony]

During a recent encounter a man ejaculated on my backside, and it went into the crack, and I felt it on my anus.  Can you please let me know what risks if any I have incurred and what testing plan if any I should pursue to make sure this exposure didn't lead to an HIV/STD infection?  Thanks for all you do.

[H. Hunter Handsfield, M.D.]

To the forum. Thanks for your question.

We get fairly frequent questions about superficial exposures of this sort. On the one hand, there are no data on which to base a scientific estimate of risk.  OTOH, even with analintercourse to completion, with internal ejaculation, if one person is infected the average chance of transmission is somewhere around once for every 200-500 exposures. In addition, to my knowledge there has never been a reported case of HIV infection that appeared to be acquired by mere contact of the anus with infected semen.

For those reasons, I am confident you are not at risk from this exposure and I do not recommend testing for HIV or other STDs. Of course everyone who is sexually active outside a mutually monogamous relationship should be tested for HIV and the treatable STDs (gonorrhea, chlamydia, syphilis) from time to time, like once a year. Therefore, if you have not been tested recently, this is probably a good time to do it. But definitely not because of this particular exposure.

I hope these comments are helpful. Thanks for your kind comments about the forum. Best wishes – HHH, MD

[pantaloneypony]

Thank you for the response.  I will follow your suggestion on regular, occasional testing but in the meantime it seems as if I wouldn't be wrong in putting my fears to rest over this one particular incident.  It is a relief to receive an answer with more nuance than "everything is risky!!" which seems to be what every other resource out there says.  It sounds as if there is some risk here, but on an individual incident basis it's going to be mathematically negligible if I factor in that the person probably doesn't have an STD, that the lack of penetration probably makes the odds much smaller than the ones you cite, and so on.  Would you put this activity in the "struck by lightning" category you mention in other responses?  

[H. Hunter Handsfield, M.D.]

I agree exactly with your "mathematically negligible" statement, and also that most health education and other resources take a conservative approach, often on the basis of their attorneys.  If there is any theoretical risk at all, many do not distinguish between realistic and unrealistic risk.  We take pride in our more objective evaluation and advice about transmission risk.

Best wishes--  HHH, MD