even though zombies are old news . . .

From cracked.com,

5 Scientific Reasons a Zombie Apocalypse Could Actually Happen

#1 Nanobots

#2 Neurogenesis

#3 The Real Rage Virus

#4 Neurotoxins

#5 Brain Parasites

go here to see: 1 - What they are seen in, 2 - What are they, 3 - How it can result in zombies, and 4 - Chances this could cause a zombie apocalypse