there was a post-apocalyptic-setting doujin I had saved once upon a time, where essentially the virus not only made the zombies aggressive hunters, but also sexually aggressive.
the protagonist basically picked up a young female along the way who basically turned out to be infected and had some kind of futa situation going on as well. at one point in a dream-sequence-but-not-really-ish situation while on the run, the infected girl hungrily rapes the female protagonist, including with a prehensile penile tail like pic related. would have loved a little more story on that note.
I think the whole thing was originally Spanish-language, although I had it in English. I've tried to find it and am even looking for it right now. if any clues lead to its capture I will be happy to post in full, it was very enjoyable if a little bizarre.