“Cabin Fever” is not what it appears to be. Sometimes it is, but not always. This all has to do with a somewhat confused script and a first-time writer/director (Eli Roth) who is always two steps ahead of himself, sometimes ending up flat on his face. But like a good David Lynch movie or William S. Burroughs book, confusion can also be used as a vital artistic tool.

The film kicks off by introducing a cast of college kids at the beginning of a vacation from school, psyched to spend a week away from civilization in an isolated cabin. But upon leaving their natural collegiate environment, these characters become displaced not only from their normal physical location — they somehow slip into an entirely different genre than the one they were meant to occupy.

The innocent and eager Paul (Rider Strong, “Boy Meets World”) and his troupe were meant for the world of the teen sex comedy, like “Porky’s” or the “American Pie” films — not the George Romero/David Cronenberg-style existential blood bath they’ve wandered into. This dislodgment from their purposed genre results in pure teenage irrational violence and twisted amounts of mental anguish.

But before a flesh-eating disease begins to evaporate the group of friends, Paul is lost in love for his good-girl, perpetually sweater-clad best friend Karen (Jordan Ladd, “The Specials”), until she manipulates his teeming sexual awkwardness on a raft and discusses over a campfire her past five-day drug and alcohol binges, during which she was accompanied by groups of older men.

Their friends Jeff (Joey Kern, “Grind”) and Marcy (Cerina Vincent, the naked girl from “Not Another Teen Movie”) are the horny antithesis of Paul and Karen’s seemingly cute, best-of-buds relationship and are constantly stealing away to have sex. And then there is Bert (James DeBello, “Detroit Rock City”), who bets he can drink only beer for the entire week and shoots squirrels “‘cuz they’re gay.”

The characters quickly become discombobulated when a diseased hermit knocks on their door. The resulting chaos leaves their car totaled and a scorched, rotting corpse basking in their water supply.

“He came to us for help and we set him on fire,” Karen says later in the film, evoking both hilarity and horror. The rest of the movie tries its best to jumble genre conventions even more while it rides a foamy wave of nihilism to a breaking point of deteriorating skin and teenage humor.

As the disease spreads, each character deals with his or her genre displacement in a different way. One becomes homicidally fevered and ready to kill anything that moves, while another grabs the alcohol and heads for a cave, waiting for everyone else to die out first.

DeBello does a wonderful job as the funny guy who realizes the joke is over, and the film’s mid-section is held together almost solely by his performance. The film’s other star proves to be the over-the-top, curdled, splashing sound effects. Vomiting blood has never been so entertaining, and Paul and Karen’s bedroom scene proves way too memorable for comfort, as Roth continues to play around with teen-sex-comedy traits.

But some scenes become too weird, like the backwoods family who runs the gas station and their karate-choppin’ offspring, who belt out the word “pancakes.” One scene is an overacted homage to “Night of the Living Dead,” and the film’s finale will either have you walking away disappointed or vomiting out your own theories that the film is a campfire-tale analogy or a nod to fans of meta-theatrics.

The idea of genre-character displacement and the original use of gore production let “Cabin Fever” exist in a fairly unique cinematic realm — one that should definitely not be missed.

Grade A/B