Might there be a real-life zombie apocalypse one day? Not likely, but then again, the way zombies have chomped their way into our pop culture the last several years, it’s maybe a bit less implausible than it once was.

What IS increasingly quite plausible, alas, is a scary global pandemic, and “World War Z,” the long-awaited Brad Pitt thriller, cleverly melds that real-life threat into the more fanciful zombie premise. Talk about more bang for your buck: Once you’ve settled back into your seat after a good snarling zombie chase, there’s nothing like the thought of a SARS outbreak to get the blood racing again.

But let’s just say right here that the one apocalypse you won’t see in “World War Z,” based on the 2006 novel by Max Brooks (son of Mel), is an artistic one. There was lots of talk about this mega-budget 3D movie, co-produced by Pitt and directed by Marc Forster, falling on its $200-million plus feet, what with a postponed release, a re-shot ending, endless script drafts and major crew changes along the way.

But in the end, it’s pretty much what you’d want in a summer blockbuster: scary but not-too-gross zombies, a fast-paced journey to exotic locales, a few quite thrilling action scenes, and did we mention Brad Pitt?

Oh right, we did. Surely this isn’t a performance to rival Pitt’s work in “Moneyball” or “The Tree of Life,” but given the lack of time for nuanced character development, it hardly seems meant to be. What Pitt offers the film is pretty much what his character, a level-headed former U.N. investigator, offers the endangered planet: Nothing too flashy, just a comfortable, intelligent presence that keeps things grounded and just might win the day.

That last part, of course, remains to be seen: The filmmakers hope “World War Z” is just the first in a franchise. And so, the story may have a long way to go.

But the beginning — especially the first half of this movie — is promising. As fans of the book know, it was written as an oral history, a collection of individual accounts. The filmmakers wisely ditched that format for the sake of immediacy.

We begin in Philadelphia, on a sunny morning in the kitchen of Gerry Lane (Pitt), his wife Karin (Mireille Enos, expressive well beyond her few lines), and their two daughters. We learn quickly that Gerry has abandoned his former harrowing work — investigating crimes in places like Rwanda, Bosnia and Liberia — in favor of a nice home life.

As the family drives off for the day, though, life changes in an instant. The streets of Philadelphia are suddenly and terrifyingly overrun by packs of wild, raging zombies. Once bit, it takes only seconds for a human to turn into one.

Talk about a leadership vacuum: The president is already dead. Thanks to his former U.N. boss, Gerry’s family is whisked to an aircraft carrier, but there’s a wee price for this protection: Gerry must head out to find the source of the outbreak.

For an hour, the action is swift: Clues gathered at a prison complex in North Korea lead Gerry to Israel, the only country to have smartly employed the use of walls, artificial and ancient. But then those persistent zombies stretch themselves into a teeming, terrifying tower of un-humanity. Gerry escapes just in time — for a seriously harrowing plane-crash sequence.

The final act takes place on a dramatically smaller scale, and at a slower pace. Not to give away too much, but this is where Gerry’s scientific instincts — and that Brad Pitt calm — will come into play.

It’s worth noting that there are, amid the mayhem, occasional touches of humor. And one of them serves as a prudent reminder — to turn off those cellphones. After all, it’s not just your movie-going partner you’ll annoy here.

Cellphones also happen to awaken zombies. Consider yourself warned.

“World War Z,” a Paramount Pictures release, is rated PG-13 for intense frightening zombie sequences, violence and disturbing images. Running time: 116 minutes. Three stars out of four.