The Department of Homeland Security last month urged people to prepare for an end-of-the-world zombie apocalypse.

Seriously.

Or at least semi-seriously.

The idea is that when government officials warn people to be ready for earthquake, flood, or terrorist attack, they’re often ignored. But if they shout “Zombies!” people get caught up in the fun and may actually put aside a case of water and a flashlight.

The Centers for Disease Control and Prevention launched a tongue-in-cheek – maybe it’s tongue-through-cheek – zombie-awareness campaign last year. And the CDC isn’t the only agency to go dead. Health departments, libraries and colleges are feasting on zombies to draw attention, sell programs and entice prospective clients and students.

Michigan State University offers a new course, “Surviving the Coming Zombie Apocalypse,” which examines how humans behave in catastrophes. A new minor in pop culture at the University of Baltimore includes a class on the social relevance of zombies.

“They are probably the most unique, the most potent reflection of our fears, because they are the closest to us,” said University of Baltimore visiting professor Arnold Blumberg, coauthor of “Zombiemania: 80 Movies to Die for.” “They’re your family, they’re your friends, they’re yourself.”

And they can be kind of fun.

The American Dental Association and PopCap games have started a “Stop Zombie Mouth” campaign to prevent tooth decay. Missouri conservation officials employ zombie imagery to promote hunter safety.

“Falling from a tree stand can injure you or make you dead,” the Conservation Department website says. “Falling from a tree stand into the gaping maw of a zombie can make you undead.”

Zombie crawls – it’s hard for zombies to run – take place in cities from New York to Los Angeles, organized to celebrate Halloween, raise money, or just for fun. Philadelphia’s seventh annual crawl is set for Easter, to be led by Zombie Jesus. (The promoters say Jesus, by definition, is the world’s best-known zombie.)

Yet some take the idea of a zombie apocalypse more seriously. Last summer’s savage cannibal attack in Florida set off a wave of foreboding, forcing the CDC to issue a formal statement denying that the end was nigh.

“CDC,” spokesman David Daigle told the Huffington Post, “does not know of a virus or condition that would reanimate the dead.”

Which is a big relief.

But plainly, if the 2000s were the decade of the vampire, then the 2010s are the dawn of the dead.

Why? Experts say the national consciousness suffered a dark and damaging blow in the terrorist attacks of Sept. 11, 2001. And since then, fear has become a default American mind-set: Political upheaval in the Middle East. Economic upheaval at home. Wars in Iraq and Afghanistan. Rebellions. Global warming. Killer viruses. The rise of the security state.

Not to mention the reliance on advanced technological grids to light our cities and speed our communications – and which threaten to plunge us into darkness and silence if they fail.

Zombies are here now, authorities say, because we brought them here, a manifestation of the age. It’s no surprise that Frankenstein and Dracula hit theaters during the Depression, one the symbol of a clanking, brain-dead economy, the other a bloodsucking capitalist. Or that George Romero’s “Night of the Living Dead” appeared in 1968, amid the carnage of the Vietnam War and the fear of nuclear extermination.

“I don’t think it’s an accident that zombies have become popular,” said Lehigh University associate professor Dawn Keetley, who is editing a book about “The Walking Dead,” the AMC television series. She added that “the terror threat, the economy — people are starting to imagine the end of society as we know it.”

And in a weird way, she said, to long for it. If there’s no society, that means no taxes, no mortgages, no worries about unemployment.

The only worry is staying alive, in continually seeking to remain one of “us” and not become one of “them.”

“When we have zombies, the survivors – and of course we’d be survivors – get to pick up guns and keep ‘them’ out,” Keetley said. “An apocalypse without zombies would be kind of boring.”