To date there have not been studies done in ME/Fibromyalgia patients on various bodily tissues in relation to the prevalence/concentration of the XMRV retrovirus. It would be interesting if in the fullness of time it became evident that XMRV may be more 'concentrated' in tissues or organs where ME/Fibromyalgia people manifest their WORST symptoms. So for example; - For those with extreme headaches/cognitive dysfunction/brain fog/fatigue - XMRV may be more evident in the BRAIN. - For those with neurological type, neuropathic symptoms, XMRV may primarily reside in the SPINAL CORD, thus affecting the nervous system. - For others who have severe gastrointestinal symptoms, then XMRV may be resident primarily in the GI tract. etcetc. This could explain why although we may have many symptoms in common, some symptoms are more troublesome in any given individual and therefore cause varying degrees of related disability/pain etc in that focus. Obviously other factors such as genetic influences may also play a role but it would be interesting nontheless to see if there was any correlation!