Paramount Pictures

In this summer's big-budget zombie apocalypse film "World War Z," Brad Pitt plays a U.N. investigator trying to find a cure for a global zombie pandemic. Based on the book of the same name, the film is uncommonly … well … brainy. There's surprisingly little gore, and the film examines the social and political repercussions of its scenario, on a global scale. We take a look at the science behind the fiction.

Warning: We've tried to be careful about revealing too many plot details of the film, but the following discussion does contain some minor spoilers.

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Fiction: In the film, Brad Pitt's character Gerry Lane is tasked with finding the source of the zombie pandemic. Attended by a crack military squad, Lane is dispatched by military plane to various overseas spots in search of "patient zero."

Science: Sometimes referred to as the primary case or index case, "patient zero" is the first person infected in a defined population of an epidemiological investigation. The term originated in the Centers for Disease Control and Prevention (CDC) during investigation of the the HIV virus in the United States. The index case can help investigators find the source the disease and determine how it spreads.

Lane infiltrates a zombie-infested research lab.Paramount Pictures

Fiction: In an attempt to find a vaccine for the zombie virus, Lane and his team must retrieve samples of live viruses kept in a secured lab managed by the World Health Organization. The good news is the lab still has electricity and the virus samples are safely secured. The bad news is that particular wing of the lab is infested with dozens of zombies.

Science: Virus samples are critical to the creation of vaccines, which are often weakened or dormant forms of the disease-causing microbe. Hundreds of thousands of virus and bacteria samples are kept in research labs around the world, including Ebola variants, smallpox, anthrax and bubonic plague.

World War Z's feral zombies climb over each other to scale a quarantine wall.Paramount Pictures

Fiction: In the film, the zombie virus quickly kills any human it infects, then reanimates the body through an unknown mechanism. Hence the term, the living dead. The scientists in the movie despair of ever developing a therapeutic vaccine, since the infected have no circulatory system. They also rule out infecting the zombies with a different virus, since viruses require a living host.

Science: Despite the best efforts of mad scientists throughout history, the goal of reanimating the dead -- by viral means or otherwise -- has proven elusive. Although it all depends on how you define your terms. CPR has brought thousands of people back to life after the heart and lungs have stopped working on their own. The nascent field of resuscitation science explores the increasingly blurry lines between what we consider life and death.

In the film, one possible disease vector of the zombie outbreak is black market organ transplants.Jens Kalaene/Corbis

Fiction: "World War Z" uses a classic science fiction technique to add detail and realism to the narrative: The film provides scraps of information, delivered in throwaway lines, which suggest that even more intriguing story lines could be explored, had the movie gone a different direction. In one such casually delivered line, a scientist suggests that the zombie pandemic could have been spread by way of a black market for human organs.

Science: Unfortunately, the black market organ trade does indeed exist. Illegal kidney procurement networks have been uncovered in Brazil, South Africa and Eastern Europe.

In one of the film's most shocking sequences, zombies overrun the walled city of Jerusalem.Paramount Pictures

Fiction: As part of his mission to track the source of the zombie virus, Lane travels to Israel. Government officials have managed to avoid a widespread outbreak by completely sealing the country's borders and erecting a massive wall around a portion of Jerusalem. In an interesting twist, officials let in all uninfected Israelis and Palestinians, and the two groups make peace within the walls. As one military commander explains: "Every person we let in is one less zombie we have to fight."

Science: Israel has several separation barriers, including a series of fences and walls in the West Bank and Gaza Strip, and along its borders with Egypt and Syria. The historic Walls of Jerusalem surround a 0.35 square mile area know as the Old City. The walls were built by the Ottoman Empire in the 16th century.

The virus in the movie kills and zombifies within seconds, causing panic and mayhem.Paramount Pictures

Fiction: In several scenes throughout "World War Z," we're shown how the zombies are able to quickly overrun defensive outposts. Once bitten by an infected zombie, victims die and rise as zombies themselves within seconds. So if even one zombie gets through to an occupied area, you'll have a hundred zombies within minutes.

Science: No viral or bacterial infection has even been known to kill within seconds or even minutes. The Ebola virus and the bubonic plague can kill within days. And certain types of gangrenous infections can kill within hours by triggering systemic toxicity.


Fiction: In the book "World War Z," which is set in a fictional near-future universe, Iran and Pakistan go to war over refugee issues, leading to an exchange of nuclear weapons that destroy each country's major cities. In the film, this event is never depicted directly, although it's referred to visually when an ominous mushroom cloud rises in the distance.

Science: Pakistan is one of nine countries in the so-called "Nuclear Club" -- states believed to have active nuclear weapons programs. Of course, Iran's nuclear weapons program is rather famously in flux.