The theoretical models for ME and MS are basically the same; autoimmune, viral, or metabolic. That's why I get cynical about ME research because they can't even figure out which way to go in MS research with tons more money than we have.
I don't doubt that MS could be viral. The point is that the studies that have compared ME and MS show they are totally different biochemically. It appears that in MS the inflammatory response is running away, in ME it appears to be suppressed as a protective mechanism. The treatments that seem to work in MS are ones that downregulate the inflammatory response, and the treatments in ME that seem to work are those that upregulate it.