World War Z not just a zombie flick - Pitt

Brad Pitt wants to assure anyone who thinks World War Z is just another zombie film: they couldn't be further from the truth.

Pitt pointed out during his first trip to Australia the film is different from zombie movies like George Romero's Dawn of the Dead or comedy Zombieland.

"If you think this is your typical zombie movie you're in for a shock because it has nothing to do with that genre," he said in Sydney.

"It's a big global pandemic."

Pitt says the movie "does not let up" after a virus rapidly begins to spread across the globe, turning humans into the undead.

Based on the post-apocalyptic horror novel by Max Brooks, the movie has deviated from the book to follow one character - ex-United Nations investigator Gerry Lane.

Played by Pitt, Lane must journey around the world, from South Korea to Israel and beyond, to find a cure for the virus and be reunited with his family.

Director Marc Forster says there are always two stories on the go.

"On one hand is this very intimate family story with a lot of heart, versus this huge epidemic outbreak," he says.

Aside from the story, there was one significant difference between World War Z and other zombie films.

Money. World War Z had a lot of it. And has a lot of it on the line.

Back in 2002, Danny Boyle's 28 Days Later was financed for US$8 million. In comparison World War Z, which is being produced by Pitt's company Plan B, is around 25 times that.

The production woes of World War Z have been closely followed, with Vanity Fair writing that 40 minutes of the film had to be completely re-written and re-shot to fix the ending.

Reports say the budget ballooned to around US$200 million, while others have speculated that with marketing costs, it may have climbed to as much as US$400 million.

Forster, who has made small films like Stranger Than Fiction and big-budget ones like Quantum of Solace, said the difficulty with a blockbuster like World War Z was the sheer volume of extras on set.

"When you're working with a thousand extras and you have Brad Pitt in the middle of it, you can't individually direct all of those people, so it's just more like mass mayhem," he says.

"You give them a general direction and hope it goes right. If it doesn't you have to do it again. It's always much more tricky to pull this off."

World War Z marks the first big-budget film Pitt has produced and Forster says he was able to switch between actor and producer with ease.

"The great thing about having him as a producer, he wants every dollar being spent to go onscreen and make sure that's the best movie possible because he's also in it," he says.

"He was a great ally to have."

World War Z releases in New Zealand cinemas on June 19.

- AAP