In real life, no fireman would swing his ax as judiciously as the one played by Jay Hernandez in Quarantine. Nor would a cop cuff just one hand on a person waiting to bite his face off, as Columbus Short does. People wheezing like Regan McNeil in front of a snowy TV are probably better left off alone.

And that’s before Quarantine turns into an all-out free-for-all of Good Samaritan stupidity in the final reel.

Obviously in most horror movies, things like that don’t just make you go hmmm. They make you go “Don’t open that door! What are you doing?! Don’t you know that … gah!” The problem with Quarantine is that — a la The Blair Witch Project, Cloverfield and Diary of the Dead — it aspires to that actual-event feeling. Like those films, a camera supposedly held by its characters captures the horrors that unfold.

As far as that conceit goes, Quarantine lacks the nocturnal nightmare qualities or the filmmaking polish of Cloverfield. But as a run-and-gun variation on that handheld style, it’s far more compelling than George Romero’s dog-eared Diary.

Plus, the horrors, as adapted for American by sibling filmmakers John Erick and Drew Dowdle from the Spanish-language film [Rec], are fairly hair-raising. It’s all nasty vomit, bloody attacks and fast-acting infection. Too bad the Dowdles suffer from symptomatic attacks of exposition. It might give the film’s fictional news crew what it wants, but nothing kills fictional fear like throwing in too many facts.

Quarantine starts out with the relaxed, realistic feeling of camera-subject camaraderie. Angela (Jennifer Carpenter) is a TV news reporter on location for a late-night news-feature about firemen with her cameraman, Scott (Steve Harris).

Her two escorts — Jake (Hernandez) and Fletcher (Johnathon Schaech, unrecognizable in a burly mustache) — joke and flirt with her. Time passes, and Angela’s pretty sure the night won’t be memorable as that siren never goes off.

A four-alarm fire is preferable to what happens once it does. The crew is called to an apartment building where a woman’s gone bonkers. Hotheaded cop Danny (Short) is none too happy to see the media – less so when the woman chomps his partner’s throat, people scatter, and, soon, Fletcher’s body splatters in the building’s atrium.

That would be a spoiler only if Fletcher were dead.

Like the bitten policeman before him, Fletcher rises again — rabidly foaming at the mouth and hankering for human flesh. And there’s no escaping the building — cordoned off from crowds and surrounded by S.W.A.T. and snipers aiming to kill. While scrambling for a way out, all those inside the building must avoid death or, worse yet, transformation.

There are a couple inventive moments when the camera is weaponized, as it were. Fleeting finger pointing threatens to turn deadly a la Stephen King’s The Mist. And the Dowdles allow some leavening humor, such as Angela’s snide behavior to an off-camera mother when interviewing her 5-year-old daughter.

But it’s the sound design, working like a composition of fear, that stands out most about Quarantine. As in Cloverfield, there is no score, and the audible cacophony works the nerves more than any “boo” scare. It’s enveloping work from sound designer Paul Pirola and supervising sound editor Kami Asgar.

Quarantine at least understands tension and release more than most modern horror films. It sounds like a pre-packaged community haunted house scenario, but it’s a moderately skillful exercise in style that should help get the Dowdles’ long shelved, and similarly filmed, The Poughkeepsie Tapes, into theaters.