I only have flashbacks from my childhood of some scenes, the scenes I remember are:
A group of friends go to a house/place, as they enter they see a person sitting on the ground with his back tilted and his back covered with a towel that appears to be moving, one of the characters removes the towel to find a small monster in a hole inside the person's back eating his/her flesh. (you just can't forget that scene even 20 years later)
At the end of the movie, what left of the group are leaving/fleeing the place in car, a couple are in the back about to make out, only to find out one of them is affected by a sickness and is turning into a flesh eating monster and attacking the others in the car.
The movie might include flesh melting when people get sick or something like that.