Does a virus cause ME?

Does a virus cause ME?: "The front page of today’s Independent asks whether scientists have found the cause of ME (myalgic encephalitis), also known as chronic fatigue syndrome (CFS). The newspaper reported that researchers have found a “strong link” with a retrovirus called XMRV.
This study compared blood samples from 101 CFS patients with samples from 218 people without it. It found evidence of the XMRV virus in about two-thirds of the people with CFS and less than 4% of people without the disease.
These findings alone do not prove that the virus causes CFS, because they do not show whether the infection occurred before or after CFS developed. The research paper is cautious in its conclusions, saying that XMRV “may” be a contributing factor to CFS, but the opposite may also be true: CFS may make people more susceptible to infection with this virus.
Despite these limitations, these findings will be of interest to the research community, doctors, and patients. Larger studies and research that establishes whether the XMRV infection occurs before or after the onset of CFS will be needed before any conclusions can be drawn."