A study linking a virus to chronic fatigue syndrome (CFS), also known as ME, has been withdrawn by the journal which published it.The 2009 study, in Science, suggested a mouse virus, XMRV, was linked to the illness.But in September this year, the study's authors withdrew some of their findings, saying they were based on "contaminated data".The journal said it had "lost confidence" in the study.In a statement, editor-in-chief Bruce Alberts, said the journal had decided to fully retracted the paper because of "poor quality control" - and because the findings had not been replicated.It had already published an editorial "expression of concern" in September, saying that the validity of the study was "seriously in question".'Too good to be true'The initial research suggested that DNA of the XMRV virus had been found in 64% of CFS patients and just 4% of the general population.But other scientists had been unable to find evidence of the virus and many argued that the most likely explanation was contamination of the laboratory samples.A study also published in Science in September claimed the virus could not be reliably detected in ME patients, even in the labs which originally made the link.The journal says there is evidence of poor quality control in a number of specific experiments reported in the paper, and raises specific concerns about some CFS samples being treated differently to others.Mr Alberts wrote: "Given all the issues, Science has lost confidence in the report and the validity of its conclusions."We note that the majority of the authors have agreed in principle to retract the report but they have been unable to agree on the wording of their statement."It is Science's opinion that a retraction signed by all the authors is unlikely to be forthcoming."We are therefore editorially retracting the report."We regret the time and resources that the scientific community has devoted to unsuccessful attempts to replicate these results."Experts said they were not surprised that the paper had been retracted.Prof Simon Wessely, of the Institute of Psychiatry at King's College London said: "The results were simply too good to be true."CFS is a complex mulfactorial condition with fuzzy boundaries, and almost certainly does not represent any single entity any more that it is caused by any single agent."But he added: "What is sad however is the degree of opprobrium hurled from some quarters at the scientists who correctly failed to replicate the original observation."This is not the kind of atmosphere that benefits science or patients."