A team from University College London, the Wellcome Trust Sanger Institute, and University of Oxford, all in England, says previous research linking the virus to chronic fatigue syndrome (CFS) was flawed because of contamination of mouse cell DNA samples in the laboratory.

CFS is a disorder characterized by chronic fatigue lasting six months or longer, with several additional symptoms that may include impaired memory, unrefreshing sleep, muscle pain, sore throat, and headache.
XMRV is a recently discovered virus that is closely related to a group of retroviruses called murine leukema viruses (MLVs), which are known to cause cancer in certain mice.
XMRV was first linked to CFS in a study published in October 2009, where blood samples from chronic fatigue syndrome patients were found to have traces of the virus.
The new study, published in Retrovirology, identifies the source of XMRV in CFS samples as being cells or mouse DNA rather than infection by XMRV.
The researchers say this does not rule out a virus as cause of the condition, but XMRV is not the cause.
In a statement, professor Greg Towers, a Wellcome Trust senior research fellow at University College London, says: “Our conclusion is quite simple: XMRV is not the cause of chronic fatigue syndrome.
“All our evidence shows that the sequences from the virus genome in cell culture have contaminated human chronic fatigue syndrome and prostate cancer samples.”
However, he stresses: “It is vital to understand that we are not saying chronic fatigue syndrome does not have a virus cause -- we cannot answer that yet -- but we know it is not this virus causing it.”
(Source: WebMed)