Past presumed virus causes of CFS

I recently picked up a book at my local library called: The Virus Within, by Nicholas Regush (an ABC science journalist) printed in 2001, which states that the Human Herpes Virus - 6 is the cause of CFS. During the late 1980's and early 1990's, several teams of American researchers said that they had found a particular herpes virus in people with CFS. The first such researcher was Robert Gallo, the head of the National Cancer Institute. Interestingly, Gallo had first tested CFS patients for the Epstein Barr Virus (EBV), before deciding on HHV-6.
Then Donald Carrigan at the Medical College at the Children's Hospital in Milwaukee, Wisconsin, was also testing CFS patients for a viral cause to their illness. He first looked at the cytomegalovirus (CMV) but later decided that HHV-6 was the responsible party.
Other researchers also jumped on the HHV-6 bandwagon, but, ultimately, all have failed to establish that this virus was to blame. Before HHV-6, from the late 1940's through to the early 1960's, it was stated as a fact that the polio virus was to blame. So much so that in Iceland, during the 1st modern mass outbreak, CFS was often labeled as Benign Myalgic Poliomyelitis, so what are the odds that the latest jumping-on-the-bandwagon virus label - XMRV - will also will soon fade away as no real evidence will be found to link CFS with the XMRV virus!