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What 'World War Z' gets right -- and wrong -- about viruses

In this publicity photo released by Paramount Pictures, the infected scale the Israeli walls in
In this publicity photo released by Paramount Pictures, the infected scale the Israeli walls inJaap Buitendijk / AP

The virus spreads quietly in China before being carried around the world by travel and commerce. It infects people through bites, and seemingly changes the brain and behavior of victims. Society is disrupted as panic spreads and millions succumb.

OK, so no one really thinks that a virus could turn half the world population into zombies. And the premise of the new movie, "World War Z," is far from realistic. But some of its details do bring up real-life issues, from the political and diplomatic fights about countries trying to cover up disease outbreaks, to the very real possibility of a pandemic that could wipe out millions within the space of a few months.

It’s no mistake the film suggests the zombiefying virus starts in China. Something similar really happened in 2002, with the severe acute respiratory syndrome (SARS) virus, which eventually spread to the rest of the world, killed more than 770 people and infecting close to 8,000 before it was stopped.

Chinese officials were accused of being less than honest about the outbreak, which was doubly worrying because scientists were already twitchy at the time about H5N1 bird flu. Perhaps due to years of public health diplomacy, Chinese officials have been widely praised for sharing information about the current outbreak of H7N9 bird flu, which the World Health Organization says has infected more than 130 people and killed at least 37 of them.

Similarly, there was some suspicion that Saudi Arabia wasn’t being completely open about an ongoing outbreak of a new virus called MERS, for Middle East associated respiratory syndrome. But again, after some careful health diplomacy, Saudi officials invited an international team of scientists to investigate MERS, which has infected 64 people and killed 38 of them.

Any of these viruses could cause a pandemic. Flu viruses often do – in 1918, the H1N1 flu killed or helped kill anywhere between 50 million and 100 million people. Its descendant, the H1N1 swine flu, killed more than 280,000 people in 2009 – and that was a mild pandemic.

WHO and other health experts caution that a more deadly pandemic could disrupt international trade and cause shortages in food, fuel and medicines if countries closed borders or had to shut down critical operations to prevent spread.

Of course, plenty of scary diseases already exist.

In both the book and the movie "World War Z," experts at first believe the zombie virus is rabies – which is indeed transmitted through bites or through organ transplants and which can make some animals highly aggressive and sensitive to sound.

But while the movie depicts infection taking hold in an unrealistic 12 seconds, rabies can be scarier because it can take months to show symptoms. Infected bats can bite people who are sleeping or otherwise unaware, and victims and their doctors may not suspect rabies when they eventually do become ill because the time between the bite and symptoms can be so long. And once symptoms appear, it’s almost always too late to vaccinate. There’s no treatment, and rabies is almost 100 percent fatal.

Rabies usually makes victims sleepy and disoriented, but it spreads in the animal kingdom because it can make animals aggressive. Raccoons, which normally prowl after dark, will boldly walk down streets, and “mad” dogs are notorious for chasing down other animals and people. Even cattle can become aggressive when rabid.

But usually it’s not a virus that changes behavior. Parasites are far more likely to do that – most notoriously, the Toxoplasma gondii parasite that makes mice actively seek out cats.

It’s evolution in action, because the parasite needs to be inside a cat to reproduce, so making mice unafraid of cats helps the parasite survive and propagate. There would be no obvious evolutionary reason for the parasite to affect people mentally, but a study last year showed that women infected with T. gondii were 1.5 times more likely to commit suicide than uninfected women.

Another study suggests it might sometimes trigger schizophrenia and bipolar disease.

And the parasite is common – a third of the world’s population is infected, by eating undercooked meat, touching infected cat feces and sometimes by eating unwashed vegetables.

Most successful parasites alter behavior just slightly, says Janice Moore, a biologist at Colorado State University who studies parasites. "If you are a sexually transmitted disease, the chances are you are not going to kill somebody overnight," she says. "No. You are going to wait."

But they get nastier if you are a bug. "There are fly larvae that actually live inside caterpillars and eat their insides," Moore says. "As the larvae crawl out of the caterpillar, they actually cause the caterpillar to defend them (from predators)."

There are scarier infections even than these. Hemorrhagic fevers, including Ebola but also yellow fever and severe cases of dengue, are painful ,incurable, and cause frightening bleeding out of the eyes, mouth, under the skin and internally. Just last year researchers identified a new virus in Africa that was related to rabies, but causes Ebola-like symptoms.

The virus, named Bas-Congo virus, killed two teenagers in 2009.

Even though films rarely portray disease outbreaks accurately, they are nonetheless a great excuse for communicating important messages about disease. A team at the Centers for Disease Control and Prevention created a stir with a zombie-themed preparedness campaign that won national attention for what can be a boring, if worthy, message

"If you are generally well equipped to deal with a zombie apocalypse you will be prepared for a hurricane, pandemic, earthquake, or terrorist attack,” the CDC’s Dr. Ali Khan said at the time.

Some government public health experts have sniffed at the campaign, although the CDC team that came up with the idea won a communications prize from the Health and Human Services Department in 2012 and wide praise from communications experts.

"In Laos, where I just finished working on health emergency communication, there is a very serious dengue outbreak. The Health Ministry lists radio, TV, and puppet shows as media for pushing dengue knowledge and precautions," says risk communications specialist Jody Lanard.

"I suspect zombie puppets wouldn't work in Laos, but zombies are hot in the U.S. So for heaven’s sake, let zombie movies carry the message.

"A movie about a disaster is a good teachable moment — a surrogate for a real disaster, which is an even better teachable moment. If the movie is gripping, the audience imagines itself in the scary situation, and temporarily becomes very interested in what they can do about it if it happened to them in real life."