Thanks for the paradigm:
  toxicity plus virus = disease causation.

What's lacking is proof for the virus involvement.

Can you give me a seminal study as evidence for the poliovirus?

Re West Nile virus,

The seminal 1937 study, in Africa, for West Nile virus is problematic. David Crowe went into that circa 2000, and we went over that study together. It is cited as the study that established West Nile virus as a causative virus, yet there was no electron microscope then to confirm a particle. Toxicology was omitted. The scientists appeared to have "adapted" the "virus" to the animal model before conducting the study, which would have biased the study. 

Jim West