Zombie Apocalypse

Okay, so there are so many ways that the zombie apocalypse will start. Virus, government experiments, etc. I believe that the zombies will come out from a modified form of rabies. For those of you who know already, rabies is gained from being bitten by a rabid animal, and you will bite somebody else, and the disease will spread. This modified form cannot be cured, and will make the person unkillable unless the head or brain is destroyed. The great thing about this is that the zombies are fast, but can now think for themselves. They know what they're doing, and they just see humans as giant juicy steaks. What do you guys think?