The fact is, no one knows. The West Nile virus was never purified. I find no evidence anywhere in the scientific literature that the rules of virus purification and isolation were followed thoroughly.
Add to this potentially serious omission the scientific indifference to the possible role of the environment in what is being called "West Nile" illness and death.
So what does this all suggest?
A major error in understanding why many birds and some individuals are becoming ill?
An unnecessary and costly West Nile virus industry, consisting of drug development, vaccine-making, public health fiefdoms, fights for status and funding, and so on?
It would help to clarify the situation if we could get some serious air toxicology research underway. That shouldn't be too much to ask.