Hi. The CDC study didn't use a known positive sample of XMRV and they did not use the sample the WPI sent them that was known to be positive! Without having a known positive sample the CDC study of negative association of XMRV in CFS is unfortunately invalid, because the CDC are not sure their assay even works before being able to 'find' any MULV/XMRV in CFS patients. How the CDC XMRV/CFS paper was even published is unclear as it fails the most basic rigours of the scientific method of undertaking a study and that is knowing what they are comparing against, with no positive sample this was not possible, additionally the CDC was not even a replication study using the same cook book of methods to detect XMRV. Suzanne Vernon Phd (of the CFIDS Association of America) said that the CDC paper on XMRV was so poor she commented: ''“ the explanation for not finding XMRV in these samples is simple – this was a study designed to not detect XMRV using a hodge-podge sample set. “ All other negative studies of XMRV in CFS also have also never replicated the SCIENCE paper methods that Lombardi et al used to detect XMRV in CFS, thus also invalidating their ablity to find XMRV in CFS patients by default. The fact is no one using the same method of Lombardi et al in the SCIENCE paper trying to find XMRV in CFS has yet failed to discount what the WPI found, that is very important for people to know.