Letter from Scottish CMO Harry Burns to Convener of Scottish Cross Party Group on ME XENOTROPIC MURINE LEUKAEMIA VIRUS (MLV) – RELATED VIRUS (XMRV) I have now had comments back from Scottish virologists. Clearly, your enquiry stimulated significant discussion amongst the group. They tell me that although they would very much like to be involved in looking for an effective cause for chronic fatigue system, they believe that recent publications looking for XMRV DNA in patients with CFS is not a worthwhile exercise. I understand thet Prof. Peter Simmonds has already looked for evidence of XMRV in stored samples from CFS patients and has been unable to find any evidence of this infection. I understand it has previously been claimed that the virus has been associated with prostate cancer but again could not be found in two recent European studies.The virologists tell me that contamination of chemicals with mouse DNA is frequent and not always recognized, and the weight of evidence is now building up to suggest that the paper recently published by the research group in the USA may well have suffered from from problems of contamination. The Scottish virology group remains willing to be involved in potential investigations to Link CFS with a viral infection in the future, should suitable candidates emerge. I am sorry this does not appear to be the answer to this difficult complex condition. Kind regards.