I took Microbiology as a prereq for RN school. For weeks after I got an A in that class, I couldn’t eat anything without imaging all the microbes, everywhere, on everything! The STD section of RN class didn’t put me off sex at all. I ended up as a OB/Gyn RN and know many doctors who became OBs for the challenges and rewards of helping families. And those brand-new residents on the OB rotation seem as interested in sex as everybody else.
Well, now I know what I have to look forward to… 
I guess I do that sometimes with strangers, or with people on TV shows. I have a tendency to think of the diseases and conditions that my friends have a lot more often already. Eg. she has asthma, he has diabetes, she has Chron’s…even when it’s not relevant to a situation. It’s just closer to the front of my mind.
My two cents: Any sex drive diminishment in med school is going to come from the long long hours of study, not from icky stuff read about or experienced. Not that I personally (ahem) had any trouble in that regard.
Prospective MDs expecting temptation to affect them in their work have probably been led astray by TV and Eyes Wide Shut. Poor Tom Cruise - examining all those semi-hot, flirtatious women all day. The reality is far more dampening.
There are certainly sleazes who get through the filters and wind up in medical practice, but I doubt they are overrepresented in OB/Gyn, at least that’s not the impression I get from news stories and the semiannual rundown of suspensions and license revocations in the state medical board newsletters. While OB/Gyn was near the bottom of my list of potential specialties, the people who go into it, male or female, find the work challenging and rewarding. It seems to me that women would be more comfortable with a woman OB/Gyn, but there are plenty who actually prefer a male doc. I see no problem with males entering the specialty, no more than a woman being a urologist (though why they’d want to palpate prostates all day is beyond me). Urology was near the bottom of my list of interests as well. But I digress.
For awhile I taught some med school Pathology classes and one of the lectures given to me (believe me, I did not request it) was an hour on The Penis and all the STDs and other diseases to which it is subject (including a set of dodgy Kodachromes). If anything was going to damp down sexual interest among med students, it was that class, not that I ever heard of any mass outbreak of chastity afterwards.
Well if movies are anything to go by (;)) The Big Book of Scary STDs sure didn’t help that cute girl in Rules of Attraction.