The above map illustrates the frequency with which the word "zombie" was entered into Google's search bar by geographical area. It is clear at first glance that only the developed world, and especially only the developed English-speaking world, seem concerned.
I have a theory that zombies are the quintessential Post-Modern horror. Gone are the days when vampires and werewolves scared the piss out of people, contemporary culture even finds them "sexy" now. Why?
Modernity, generally defined as that period that lasted from around 1517 through 1914 or so, is characterized chiefly by a breakdown of the Medieval Synthesis between Christianity and traditional philosophy. As such, in the Modern Era thought on every topic fractured into two opposing camps: realists vs. idealists, rationalism vs. fideism, rationalism vs. idealism, etc. This polarization of ideas manifested itself culturally as the cold, calculating Enlightenment on one side, and the mushy, nostalgic Romantic Movement on the other.
As a result of this fracturing, throughout the Modern Era we can pick up on two chief currents in what frightened people. Those of a more rationalistic bent were frightened by the prospect that they might be wrong about the operation of the supernatural in the world. The Puritans were famously willing to go to great lengths to rid their communities of suspected witchcraft. Likewise, Bram Stoker's Dracula seems to me to be the tale of a sorcerer first, and a "vampire" second. We can also include "mummy" horror here, as essentially a fear of magic.
On the other hand, those who reacted against the Enlightenment and embraced the opposing sentimentality of the Romantic Movement were frightened by the prospect that they might be wrong, and the world might just be a kind of Deistic experiment. Thus Mary Shelley's Frankenstein, which told a story in which it was proved that the world is mere mechanism.
Historically, the Romantic Movement was a reaction against the Enlightenment. It sought, by a last ditch effort to appeal to our emotions, to restore some of what the Enlightenment had destroyed of the old culture. Interestingly, following this challenge of the Romantic Movement, the fears of the more rationalistic bent began to shift from witchcraft and the supernatural, to over-sentimentality—a reaction against a reaction.
In this category we find the later vampire mythology, in which they are presented as over-stimulated "romantics" with a metaphorical "lust for blood." Much the same can be said of werewolves, who are ruled by bestial passion.
Post-Modernity, though, is characterized chiefly by a denial of any meaning or purpose to anything. Where Modernity (in both Enlightenment and Romantic forms) sought to replace the traditional culture and philosophy with its own, Post-Modernity offers no contrary hypothesis, it simply denies that there is culture. To put it another way, Modernity sought to reform the truth, Post-Modernity seeks to abolish it outright.
Not surprisingly, Post-Modernity is accompanied by a whirlwind of technological innovation. In a world where actions have no moral repercussions, and men no responsibility, we might as well build the bomb, if only because we can.
The Post-Modern world is founded on technology. If the Middle Ages were founded on religion (albeit in cooperation with reason), and Modernity was founded on ideas, Post-Modernity is founded on stuff. In other words, when you throw religion, morality, and, finally, reason and truth itself out the window, all you've got left to do is seek your own comfort and pleasure. And that's exactly what we have done, and been marvelously successful—the crowning achievement of this technological pleasure-seeking being the removal of the consequences of sex.
What, then, could possibly frighten Post-Modern Man, tucked away in his fortress of comfort (I think they call them Man-Caves now)? Simple, a world in which one has no time to seek pleasure because he's too busy fighting for his very survival. I can't be the only one who's noticed the really astounding frequency with which tales of a post-Apocalyptic, dystopian horror have been produced in the decades since the '70s, especially if you include disaster movies, which are basically the same thing.
Like the Moderns before us, we look at the things that terrify us and see ourselves gone wrong. Mary Shelley looked at Dr. Frankenstein and saw a man willing to do awful things as a result of his inability to see life and humanity as more than just machines and scientific principles. Bram Stoker looked at Dracula and saw a man that terrified him because of the incredible things he could do as a result of his sorcery. Post-Modern Man looks at zombies and sees creatures who care nothing for comfort or pleasure, who desire only to feed a ravenous and insatiable hunger and, as a result, are capable of destroying anything that stands in their way.
The map above illustrates this point rather well. If, at its core, the fear that zombies and other post-Apocalyptic tales inspire is based in our fear that we might have to give up our technological conveniences, then it would only affect the first world. After all, it's sad to say in a way, but if Mad Max came true, life in Central Africa wouldn't change that much. It doesn't make a lot of sense that they would be too worried about it.