Olmstead REQUIRES the virus before the disease happens. The title even says the virus exists and is old. It is ONLY the virus that causes Polio. Olmstead argues that other factors can make the virus more virulent. At no point does Olmstead take the position that polio can occur without the virus being present. He points out his critics make that claim but he doesn't accept or promote that position.Agreed, but let's get back to where this started. You asserted that Dan Olmstead provided "no evidence that polio is caused by factors other than a virus". I pointed out solid evidence that he does and that said evidence is in the title of one of his articles. Again, here's the article in question:
The Age of Polio: How an Old Virus and New Toxins Triggered a Man-Made Epidemic
You did not present any solid evidence that he said polio is caused by something other than a virus. You completely ignore what he writes and try to pass his critics off as if they were actually Olmstead. They are not.