The world is headed for a dead-end on Dec 21 2012, according to firm believers of the Mayan Apocalypse prediction, bur for some in the United States, Earth will not be engulfed by destructive rains of fireball or inundated by gigantic tsunami flood.

Instead, this planet will be overwhelmed by a mysterious virus that will morph those infected into zombies and will drive mankind into the brink of extinction.

This scenario directly alludes to The Walking Dead, the hit TV series that showed a chaotic world reduced to a virtual standstill, in which survivors were forced to take last-ditch stand to fend off the army of zombies that swarmed and overrun the cities.

However, these horrific implications were not necessarily confined to comic books, according to the Discovery Channel documentary 'Zombie Apocalypse' that will air Dec 18 in the United States.

In a preview clip, which is viewable through this link: http://www.hollywoodreporter.com/live-feed/could-zombie-apocalypse-ever-happen-401910, a group of Americans were shown honing on their weapon skills to fight off the undead in the event of the virus outbreak.

"A zombie apocalypse happening is not a question of if, it's a question of when," one of the trainees was quoted by The Hollywood Reporter as saying.

Theoretically, these armed groups are not preparing for nothing, according to Dr Robert Smith of the University of Ottawa.

"A zombie pandemic ... is something that is plausible, it's something that at least in terms of spread, is very likely," Dr Smith said in the Discovery documentary preview.

He added that one person, for instance, in New York City succumbing to the zombie virus could potentially spread the plague in a very short time, likely spawning new dead walkers by the hundreds of thousands.

In just over a week, the more than eight million population of the Big Apple could end up with herds of zombies terrorising and mindlessly overrunning them, Dr Smith said.

Dr. Steven Scholzman of Harvard Medical School is fully supportive of the assertion. He explained that "the most likely ideology for a zombie pandemic would be a viral outbreak, a mutated contagion most likely a virus."

By natural design, "viruses are fascinating organisms and would be very effective at changing us into something approaching the zombies," Dr Scholzman said.

"They use our DNA, they rely on us to spread themselves, so it fits right into the model of zombie pandemic," he further pointed out.

The Hollywood movie '2012' depicted Earth's destructive moments in minute details and man's struggle to stay alive amidst the conflagration generated by massive earthquakes and the succeeding deluge.

Yet it could be that the closest threat to man's existence is his own self, which Discovery suggested is very much susceptible to a disease that one could one day wipe out humans from the face of this planet.