A few good points here: NK cells however play a more major role in innate immunity - the job of clearing up viruses is generally down to the adaptive immune system with T-cells and B-cells + the antibodies the B-cells produce. To me it seems a little strange that despite these results people still hold strongly onto the viral causation. I understand the argument of tissue-specific viruses but I would expect some clues to still be present in these samples. There has to come a point where we come to accept that viruses aren't the major cause of pathology in ME and I think we're fast approaching that - certainly it is worth testing these things to the fullest of our abilities but if the evidence isn't there you have to move on to other hypotheses. I think there is little argument that they are the most common triggering factor, likely due to the immune response they initiate, but if results searching for them keep turning up a blank we need to explore other areas and I think autoimmunity is both the most associated with the viral ideas and also probably the most exciting area at the minute.