The zombies in the new film “World War Z” are too fast to be truly scary. That may be a sacrilegious point in some nerd circles, but it’s a key insight derived from epidemiology and, zombies aside, it has serious implications for global health.

The rise of fast zombies — zombies that hunt like velociraptors rather than shamble like drunks — is a great and recent innovation in zombiedom. It’s what made the film “28 Days Later” such a hit. It’s why the filmmakers opted for fast zombies in “World War Z.” (The book version uses slow zombies. Author Max Brooks told the New York Times he considers fast zombies too horrifying to think about.)

Although fast zombies appear much scarier on-screen, their speed is their weakness. Or, to be more exact, their speed is their virus’s weakness. Fast zombies don’t just run fast; they become zombies fast, too. In “World War Z,” the time from being bitten by a zombie to being reborn as a sprinting, snapping, shock troop of the undead yourself is less than 15 seconds. That’s bad news for anyone in the immediate vicinity. It’s good news, though, for anyone who isn’t.

“That offers the possibility for incredible spread within a defined community,” said Jonathan Zenilman, head of the infectious-diseases division at Johns Hopkins Bayview Medical Center. “But you could surround a community and quarantine and keep it contained. You don’t have to worry about who’s on a plane to Europe.”

Fear of Disease

A scene from “World War Z” proves his point (mild spoilers ahead): A zombie ends up locked in the closet on an international flight. When a hapless flight attendant unlocks the closet, the zombie tears through the plane, creating more zombies, who in turn create more mayhem. The plane, predictably, crashes. That’s bad news for everyone on the plane. But it also arrests the spread of the disease by killing its hosts. The zombie virus can get on a plane to Europe, but because it spreads so fast and so lethally, it’s going to have trouble getting off.

Zombies, of course, are the public health community’s favorite monster. If werewolves represent our fear of the wild, aliens our fear of the unknown and vampires our fear of sex, zombies represent our fear of infectious disease. There’s a reason the Centers for Disease Control and Prevention have a whole page on “Zombie Preparedness” but nothing on Dracula.

After all, that’s what zombies, at least in most modern incarnations, are: diseased people. The zombie infection is often compared to rabies. It spreads through bites, presenting through aggression. But there’s a reason rabies hasn’t overwhelmed the Earth: It’s not a very efficient disease. Biting people is hard, and people tend to notice when you try it. That’s why Anne Schuchat doesn’t stay up nights fretting over zombies.

Schuchat, the director of the CDC’s National Center for Immunization and Respiratory Diseases, has worked on meningitis in West Africa, disease surveillance in South Africa and severe acute respiratory syndrome in China. She worries about the diseases that infect worlds — those you can’t bring down with a shot to the head. Zombies are pleasant compared with her concerns.

The really scary diseases, she said, tend to have three qualities: first, a host population that isn’t immune; second, the capacity to spread rapidly; third, severity.

Diseases face a choice between spreading easily and being severe. If a disease is too hard on its host, killing quickly, it can’t spread. If it’s too easy on its host, it doesn’t much matter if it spreads. “That’s one of the reasons we talk about the 1918 influenza a lot,” Schuchat said. “In many ways, it was a perfect weapon. Most people actually survived that influenza. The death rate was only about 2 percent. But that’s enormous across a society.” Had its death rate been 100 percent, by contrast, the flu would’ve been stopped in its tracks.

New Dangers

If globalization is influenza’s ally, the ability to rapidly disseminate information is its mortal enemy. The quicker the world knows what disease is coming, the faster resources can be mobilized and behavior can be changed to stop it. This is where reality and “World War Z” — the book this time, not the movie — converge. SARS caught the world unprepared in 2002 because authorities in China, where it first appeared, covered it up. Brooks deploys a similar scenario at the start of his zombie near-apocalypse.

China has learned a lot since then. “I was in Beijing during the SARS response,” Schuchat said. “The Chinese have come an enormous distance since 2003. They’re real models now.” Their responsiveness and transparency were tested in February when a new strain of avian flu was found in China. Schuchat said that this time the Chinese did everything right: They alerted the World Health Organization, sequenced the genome and released the results, and mounted a massive effort to locate infections.

China’s strides are not necessarily the norm. The concern today is the Middle East, where the SARS-like coronavirus known as Middle East respiratory syndrome, or MERS, has emerged, and transparency in dealing with it has been wanting.

Brooks believes that we like to consider these dangers in terms of zombies because we can calm our anxieties by telling ourselves that zombies aren’t real. “If all that happens because of a zombie plague, then you can say, ‘Oh, well, that would never happen, because there’s no zombies,’” he told the Times. But, to be a bit of a downer, the threat is real, and it’s even scarier than zombies.

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