World War Z covers genuinely new ground as far as zombie films go. Some of the first zombie films were about very local infections; Night of the Living Dead (1968) saw a survivor whole up in a house for a single night, until the cavalry arrived, sweeping the countryside and clearing all the zombies. The same with Shaun of the Dead - the Army arrives in the morning and clears everything up.
Most zombie films since then are about a few survivors in a house, in a mall, or underground, or on the road, in a world where civilisation has already passed away. Even films like 28 Days Later, where the infection only affects just the UK, is post-apocalyptic in that for the whole duration of the film there is no hint of government or of the rest of the world (i.e., in feeling it is post-apocalyptic, although not technically in fact). In Romero's Diary of the Dead and Survival of the Dead we see the infection spread anew, but, the films are away from all the action, down backroads, in woods, on an island... away from civilisation, and away from any military resistance to the plague.
“World War Z... is, truly, the first zombie war film.”
World War Z covers the middle ground - it comes after the initial infection has spread but before civilisation has fallen. This is the awesome, world-changing epoch where governments and organized armies are fighting the undead with all their weapons, intelligence services, and with international flights and airports still partially up and working. It is, truly, the first zombie war film. Little hints of "reports of rabies in 24 countries" (approximate quote) are heard from news reports in the background in the first few minutes of the film.
The strength of the Air Force and the mobility of the Navy are no match for the zombies in cities. Throughout the film we get see cities collapse and fall rapidly from a hugely violent and catastrophic spread of zombies in densely populated areas, and it is depicted perfectly. In 28 Days Later and 28 Weeks Later we see some scenes where in the flood of running bodies the armed guards cannot tell who is infected and who is running for their lives. This films takes that problem up a few notches.
When it comes to fall of cities in World War Z, there is no doubt that that is how it would happen. The opening of the film sees Brad Pitt (playing Gerry Lane, a United Nations investigator) witness the speed at which the aggressive zombies spread through the streets, with emergency services on the verge of reacting but not quite getting their act together. The same happens in Planet Terror in the hospital in the first half an hour - as the medical staff realize the seriousness of the symptoms of all the incoming patients, it is too late to do anything except a little "self preservation". In World War Z, As quickly as the police are being mobilized, the violence has spread over them. There is a sense that no evacuation plan could possibly be quick enough.
Suddenly, bam, the zombies are everywhere, in every country, and dominating every news channel.
From then it seems that most international contacts are lost; the USA's Naval command center, at sea, never receives word from India ('a black hole') and other hugely populated countries. It is Eastern Asia that it appears it started - South Korea, perhaps. Those who have read the book know it started in China although the film cleverly has the cast not quite find this out. The only presumption is that they are completely overrun. Brad Pitt sets off in search of the cause of the epidemic with a short-lived virologist - there is precedent for the fact that if you understand the genetic heritage of a disease, you can understand much of how to stop it. Wherever they go, however, they see humanity in retreat: walls are being overrun, functional airports are becoming few in number, and eventually, they are stranded while en route to a World Health Organisation research centre.
The rest of the film is set in the WHO centre. Pleasingly, many classic zombie-film devices are now in play; there are a few survivors holed up indoors, and they have to use their ingenuity (rather than brute force) to get by. They sneak past zombies, create diversions, and all the while work on their plan on creating a form of vaccine. More about that below. This is the more thrilling part of the film, with much less need for the loud-bangs and war-fighting that, at the end of the day, does not entirely suit zombie films. The aggressive zombies are more docile when non-stimulated, so the trick is to be quiet, move slowly, and be sneaky... throughout the first part of the film, we are often left annoyed that the lead characters can't take this approach more often!
The film winds up here and subsequent snapshots tell us that the WHO vaccine is slowly allowing humankind to fight back more effectively, street-by-street. We see some large-scale destruction of docile zombies and hear commentary that there are still many groups of survivors, each finding different ways to survive - we already saw that, perhaps, North Korea evaded the early epidemic by pulling out the teeth of all of its citizens therefore stopping the rapid spread of the infection due to bites. So the film ends with a clear depiction of how humankind can claw its way back to dominance, via the same type of medical science that probably created the epidemic in the first place. Nonetheless, it is a satisfying film from both an action point of view, and from a thinking point of view, and has a lot in it both for the fans of classic zombie films (with survivors sneaking around), and for fans of aggressive zombie films (with plenty of enraged zombies to properly fight against).
OK read on for some more thematic notes on World War Z.
The zombie infection is a virus. The film doesn't concentrate on the little details of how bites lead to people turning into zombies - so many zombie films show us over the course of half an hour how an infected person who dies (from a cold fever or from hir wounds) reanimated, and rises from the dead, seeking the flesh of the living. We all know how that works, and one of the great strengths of this film is that it doesn't go into this small-scale stuff all over again.
Once, Brad Pitt looks back at a victim on the ground after he is mauled by another zombie. He counts for eleven seconds before the body starts to convulse, and then picks itself up, and launches itself at the nearest living person. Eleven seconds is not a long amount of time, but this rapid conversion is required for an aggressive-zombie film. In a move that is surprisingly rare in a zombie film, a bite victim has her arm chopped off in time to stop the infection, thus 'proving' the biological nature of the infection.
For more on the neurology of it all, try my other page:
Something interesting is going on neurologically, metabolically and biologically when the recently deceased become capable of getting up and trying to kill the living. Firstly, any pathological study must start with an examination of methods of propagation, so that the disease can be contained. Secondly, we look at the role of the cortex of the cerebrum in zombies and animals. A broken cortex results in more zombie-like behaviour, so, our description of zombie biology must account for the lack of a working cerebral cortex. Thirdly, zombie bodies are special. They do not feel pain, eat or drink. Normal humans die of thirst quickly. No zombie film has explained, really or fully, how the infection causes all of these unlikely symptoms. But we shall try...”
As an aggressive-zombie film, the zombies do not suffer from rigor mortis. Their limbs are not stiff. Doctors do explain without doubt that their circulatory systems no longer function - so it is massively biologically problematic that the zombies are fast, agile and strong. With no supply of oxygen or sugar to the muscles, of course, this is always one of the worst explained aspects of the physiology of zombies.
The other main change that the virus does to the bodies (apart from creating new metabolic pathways) is rewire the brain. This is not impossible; some fungus infect ant brains, for example, and make the ants do some very specific things.
This section is taken from The Biology and Neurology of Zombies.
Zombies can always tell who else is a zombie, apart from in a few of the more humorous zombie films (in Shaun of the Dead the detection is purely visual so that with a bit of zombie makeup and some fake moaning, survivors can sneak past the undead). In the vast majority of zombie films, the undead do not fight each or eat each other, and mingle peacefully. They only attack the living. Some chemical interaction must occur: The dead can either smell who is dead, or, can smell who is alive.
If the dead can smell each other, and therefore know who to ignore, some sort of zombie pheromone must be released by the dead. If the cause of the disease is a virus, perhaps by-products of the virus' actions are detectable. Perhaps this by-product is unpleasant: If the zombies need to eat fresh meat, then decaying meat may contain poisons that they can detect.
Or perhaps it is the living who produce normal pheromones, and the dead can merely smell these (and they smell like food). This would however imply that sometimes the living could be smelled out by the dead, whereas in zombie films this never happens. In 28 Days Later one character hides behind a mirror and in a kitchen cupboard. The dead would surely be able to smell them clearly, and find them.
In both cases, it is strange that in crowded rooms full of the dead and the living fighting one another, the dead never accidentally attack each other. Even fully conscious, thinking and functioning living Humans do it, why don't zombies who have largely impaired brain function sometimes attack the wrong target? Point (1) above looks more likely, but perhaps both points play a role: The zombies can both smell the unpleasant flesh of other zombies, but also smell the fresh flesh of living humans.
In the World War Z film, a central part of the plot becomes the fact that the zombies select viable new victims and not those who are mortally ill from disease. Infection with some diseases confuse the zombies, and make them overlook certain human beings. An early comment in the film says that about 5% of the population are seemingly immune - although no such people are discovered in the film, it appears that this initial report was referring unknowingly to those have terminal illnesses that make the zombies avoid them. They flow around them like "a river around a rock" to quote from the film. just in the same way that they might flow around their follow zombies. In an unbelievably short few hours after Brad Pitt injects himself with a horrible (unspecified) virus, he is emitting a pheromone that makes the zombies ignore him.
The problem is, of course, that aside from the smell of rotting flesh, there is no such chemical aroma that indicates our general health in such a specific way, and in such strength that our unaided noses can detect it. Most horrible and fatal diseases do not cause any particular smell. The zombie virus enhances our olfactory system in addition to manipulating the brain. As these necessary properties of the virus builds up, it starts to sound increasingly impossible. I know, of course, that very few who watch zombie films care about the biological plausibility of the phenomenon, but, just take it for granted that World War Z's description of the outbreak is about as advanced as any zombie film has gotten so far, specifically for its attempt to describe how zombies can 'detect' each other and/or 'detect' the living.