Ali has a really nice discussion about STIs going on over at her blog. In my own comment (here) I discuss my own half-drafted story about Boromir's escapades with a chambermaid, which has gonorrhea as a plot element. It's really about power dynamics and where exactly you draw the line between consensual sex and rape in Middle-earth, and that's a big part of why I never finished it. It just felt too preachy, too much of an import of RL political concerns into fanfic.
But now I am thinking about it and am sorely tempted to dust it off and see if it's salvageable.
Most weeks that would be okay. But this week I really must work on my dissertation proposal, plus I have several blogging challenges coming up. And I have at least one story in the queue ahead of it to finish off. So this is really not the best time.
And yet... nuzgul.
P.S.: DO check out the thread. I'm sure Aliana would love your thoughts on STIs in Middle-earth, and you might find other folks' theories interesting, too. This topic may not feature that often in our fanfic, but that doesn't mean we writers haven't thought it through.