Finally saw this highly recommended horror movie from...2014? I thought it was more recent than that. Oh well. The short answer is: I liked it.
The plot follows a pretty college girl as she catches a sexually transmitted ghost from a guy she is dating. The rules are like the Ring if the ring was an STD. Once you have sex with someone who is infected, a ghost starts walking towards you from an unknown location. Whenever you move, it reorients to you but always moves pretty damn slowly. So, you can drive for a few hours and that will give you a couple of days to relax. If the ghost catches up with you, it looks like it humps you to death (possibly bending your body in unnatural ways while doing so). If the ghost gets you, it moves back to the last person who caught it and so on. The only way out is to pass it on and then hope the ghost never catches the person you passed it on to.
Obviously, the metaphor for STDs is strong here with no one ever really looking like they use a condom. The movie gets a little into gender politics (the pretty girl is constantly ogled and lusted after, even by her friends). There is also the drama of the unrequited love where one guys feels rejected that she didn't choose him to pass the curse onto.
The kids try to get proactive in this and figure out a way to stop the ghosts but they do so in the dumbest possible ways. For example, when the main girl passes on the curse, she gives it to a guy who lives across the street from her. So, if and when something happens to him, the ghost is just that much closer to turning around and getting her.
The ending is nice and creepy. The movie moves at a fairly strong pace. The chase becomes very fun and provides strong thrills. I would give this a B+, only marred by the idiocy of the characters.