Causes of an outbreak?

So, we've seen all the zombie films and know all the possible potential causes; Biological Weapon, Toxic Gas, Man-made Virus, modified veggies, Alien goo on meteor.. But, how many causes aren't too familiar to us, aren't over used or just completely overlooked??

Some that came to mind was:
Some form of Influenza/bacteria - Pro's: Possibly only temporary as the body fights off the virus. Cons: Spreads in more ways than just bites (airborne, human contact, saliva (kissing is out of the question, sharing water), can mutate and never be fully cured (like the cold)

Water Contamination - Pro's: Can probably be avoided by boiling water. Cons: We all use tap water for everything in life so it would most likely kill everyone before we realize it's the water, would make surviving damn near impossible for people who figure it out early.

Some form of Supernatural/Religious cause - Pro's: An answer for possession. Cons: Would it even have a cure? Exorcism would be possible but i'm not religious and it just seems too easy/farfetched

Can anyone think of any more? :)

Well, in Zombieland zombie-ism had its source in mutated BSE (mad cow disease). And in World War Z its source sometimes was called african rabies, but actually remained unsolved, because 'patient zero' showed up in China and ever since there was no officially announced declaration or explanation for zombie-ism.

And that is actually the thing I like most: Having something that literally asks for explanations and is even open to some suggestions (like within WA up until now), and yet it remains a mystery - at least to some degree.

What I would like to see is some kind of fungus like aggressive mold or something that evolved and spread in a subtropican steppe very fast and produces spores very quickly, and then finally its spores are carried by trade winds over huge distances into heavily populated regions in order to have the pandemic or humanitarian catastrophe you need for an apocalyptic event.
Storytelling advantages: pandemics based on fungus are hard to control and to treat, especially in low-tech countries; and if things start to spread into the 'modern' world, the reaction time for CDC and medical services may be too long in order to keep up with the spreading thing.

This would work for small skirmishes as well - like local incidents which provide a completely different set of issues, problems and was to solve it ...

Supernatural/ religious/ magical sources: Meh ... No, I don't like that a lot. This would literally ask for the D&D Cleric, and problem solved. Also I am more in the "realistic" or "hard SF" based zombie-theme ...

I like your way of thinking :) I too prefer the more serious approaches and causes. Your idea is really unique and paired with excellent support. It's even usable without it changing people into zombies and still make great material.

If i could give you a rep bonus or some kind of +/like.. Consider it done :P

Oh wait.. I figured it out.. You got some rep my friend

the crazies did the water thing. while the crazies isn't technically a zombie movie, it does fall into the same vein. the virus spread through the water supply, but because of how the supply feeds the town it went somewhat slowly.

That they certainly did reaper239. Their reasons for some people not changing were because it hadn't reached their house yet, wasn't it? It started with the people that were closest to the water pumps or whatever. Wasn't bad i guess.

One other cause I came up with that may not have been used yet:
Some kind of Chemical in the air that affected the Rain (Some form of Acid Rain) - Pro's: Unique, unpredictable. Cons: Would contaminate most water supplies, makes surviving too difficult again.