"We humans have a history of creating wonderful and more exotic ways to kill each other. The British actually invented Chemical Warfare and were the first people to use poison gas attacks in Eastern Europe long before WW2...so don't discount a 'Zombie Virus' being used on a population; just think about how much the Russians seem to hate the Chechens?

Personally, I can see Human Error being a major factor. Labs all over the world tend to keep some of the deadliest organisms around for testing and to make cures from, and as we know in the past agents have been used by terroists to attack urban populations...remember the Sarin attack on the Tokyo subway? Where the hell did they get that stuff? And what if the 'Zombie Virus' was just a mutated/engineered Rabies virus cross-bred with Flu for contagion enhancement like in 'Left 4 Dead'?

I personally think it'll be a First World Country where it appears first...America or England, bacause even with millions spent on security and preperations and contaiment measures, it only takes one idiot to run when he should have stayed....watch: Stephen King's The Stand for a rerally good example."