It's true that governments have been known to create versions of viruses and release them (some people believe this is why HIV appeared, a man made manupilation of SIV). As far as West Nile, I suppose its possible that it was created by somone-personally I like to think that things like this didn't happen unless its proved otherwise though. As far as I know, West Nile Virus was discovered in the 1930s-but 70 years is pleanty of time for a natural or unnatural mutation.
wow, every town but mine has been spraying, although they've stopped 2 days ago. and there's this new virus worse than west nile, being carryed by mosquitoes, blah blah blah.