With summer’s popcorn flicks winding down, a new big-budget movie named “Contagion” is hitting theaters, and it deals with a more serious subject: a flu epidemic.

And what more modern way to promote a movie about an epidemic than to leverage social networking? At least that’s the thinking of Beverly Hills production company Participant Media.

“It shows how social interaction can actually cause a pandemic,” said Christopher Gebhardt, senior vice president of digital at Participant.

The experience begins at the “Contagion” Facebook page, where visitors agree to play “Are You Patient X?” The game accesses the visitor’s name, profile and list of friends. After a few questions, the game rates the player on his or her vulnerability to a virus. It then asks for a few friends to share the test. Based on the friends’ decisions to take the test or not, the game maps how a virus would spread among the player’s Facebook contacts.

Sound grim? There’s not much of a payoff, either, aside from the game offering some guidance about how to avoid being a victim of the next great epidemic.

“Contagion,” a Warner Bros. film that stars Matt Damon and Gwyneth Paltrow, opened Sept. 9.

Gebhardt said the viral campaign will keep spreading for at least six months, past the anticipated release date of the movie on DVD.