XMRV is a retrovirus, just as HIV is, which causes an immune weakness to viral infection and cancer, and also increases inflammation. ME/CFS is a disease of immune dysfunction and inflammation and causes a high incidence of lymphoma cancer.

electron microscope photo of XMRV

Does XMRV cause ME/CFS?
It's detectable presence in 67-86% of ME/CFS patients indicates a high probability of being the cause because its presence in the normal population is only around 5%. It's real presence in patients may even be a higher percentage because it likes to hide out in tissues whereas the search for it has always been in the blood.

Successful Treatments Pointing to XMRV
In 1993 researchers used a small level of electric current to disable the infectivity of 97% of HIV in a test tube of virus and white blood cells. HIV is also a retrovirus. In 1997 I used electric current (4Hz AC) to free myself of the virus causing ME/CFS in me. Judy Mikovits says that the drug Suramin is very helpful for patients with ME/CFS. It is a drug which is very effective against murine viruses such as XMRV. So there are two anti-retrovirus treatments that are effective.

So logically it looks like XMRV is a virus which causes ME/CFS although I'm not discounting the possibility there may be others.

Reasons why the XMRV theory is suppressed:
1) Ego. Anytime someone asserts something there will be someone else to counter it. Scientists fall prey to their own egos as much as anyone else and researchers compete for prestige and government grant money.
2) Normalcy Bias. The HIV-AIDS theory was also opposed strongly. AIDS was thought to be more psychological & life style (drug use, homosexuality, partying too much, etc)
3) Judy Mikovits says that all vaccines have retroviruses that cause cancer, Autism, ME/CFS, and so the medical system is opposed to anything against vaccines because that would undermine their credibility. And silencing the XMRV theory protects the medical system from lawsuits from victims of Cancer, Autism, and ME/CFS. Science magazine, which retracted Judy's article on XMRV, is a proponent of the medical system.
4) Judy's former boss, who was very influential politically in Nevada, had her thrown in jail for 5 days without any charges against her and no arrest warrant. Her mug shot was published in Science mag to defame her. She was set as an example to others who also may want to buck the system. Judy was against an ineffective XMRV test method that her boss was selling and so that was motive against her.

The Lies Against the XMRV Theory
1) Judy's tests revealing XMRV in ME/CFS patients blood were just from blood contaminated with the same virus due to using mice for experiments in the same lab (since mice often carry XMRV).
2) Lipkin did a study and found no XMRV in ME/CFS patients blood.
3) Silverman did a positive study on XMRV but later retracted it saying he found evidence of contamination.

Responses to the Lies
1) An independent analysis of the same blood samples Judy used found no contamination of any kind.
2) Lipkin's study found no evidence of XMRV using PCR tests but did find it in 6% of samples by testing for antibodies. But he erred by excluding patients with other known infections or diseases, basically using only the least infected ME/CFS patients. And now it's known that without a special reagent the XMRV can't be detected by PCR tests. The needed reagent hadn't been developed yet at the time of Lipkin's study.
3) Some of Silverman's blood samples had VP62 plasmid contamination which is why he retracted some of his earlier conclusions. But the original samples at Judys workplace were retested and found to be free of contamination so Silvermans error was no bad indication about Judy's test methods.

Judy says that her original article published in Science magazine remains 100% correct other than an error concerning the virus genetic sequence. She calls most of the other negative studies "scientific fraud" due to their sloppiness and lack of following the same methods Judy used, as if they did it that way to assure negative results. If you want the full story of Judys findings and the struggles she had to endure against the "system" then get the $14 book PLAGUE. Judy is a hero in my mind and I think XMRV is definitely the main causitive virus of ME/CFS.

Here's some quotes from the "Plague" book:
...having met hundreds of [ME/CFS] sufferers on both sides of the Atlantic, she [Mikovits] would comment, "It's amazing to me that anyone could look at these patients and not see that this is an infectious disease that ruins lives."
Dan Peterson of Nevada, an internal medical specialist with a wait list measured in years, described what Mikovits would call "opportunistic infections" in these patients; multiple immune deficiencies; a kind of sub-acute encephalopathy [brain disease/malfunction] that lowered IQ and destroyed even the brightest patients ability to think straight, complemented by abnormal brain scans using several technologies. The doctor offered data for cytokine [immune signalling proteins] "storms", an onslaught of inflammatory proteins like interferon that leveled victims, generated in response to infections. He noted that 5 percent of patients in this carefully observed group had rare immune system cancers that would be expected to occur in the general population at rates closer to .02 percent. In all, 77 of the 300 had either blood cancers or cellular changes that were predictive of lymphoma. Mikovits was struck to her core. "It's a retrovirus" she thought, almost saying the words out loud. HIV was one of the three retrovirus families known to infect humans; maybe there were four, Mikovits wondered. Long known to infect domestic animals such as cats and cattle as well as wild animals, retroviruses caused cancer, immune deficiency, and horrendous neurological diseases. If the disease Peterson described wasn't AIDS, it was akin to AIDS or, as Mikovits would say eventually, "the other AIDS", or "non-HIV AIDS".
As long ago as the 1980's Campbell Murdoch, a local doctor in Dunedin, New Zealand, began referring patients to University of Otago microbiologist and medical doctor Michael Holmes. Interestingly the disease was known popularly in Dunedin as "Poor Mans AIDS". The South Island of New Zealand was hit by the malady by the late 1970s. Holmes, whose primary interest was "clinical immunovirology" spent several years prior to his retirement in 2002 studying "Poor Mans AIDS" for evidence of retroviruses.
In 1986, using the equivalent of $690 given to him by patients, Holmes looked at six sufferers and six healthy controls and discovered reverse transcriptase, and enzyme used by retroviruses in their replication process, in four of the six patients. Holmes wrote "We would like to propose a retrovirus etiology [causation] for CFS based not only on this pilot study but on the train of deductive observation which led us to consider it in the first place." Part of that deductive observation had been the cytokine "interferon" seen in extremely high levels in ME patients. Holmes added "the most powerful interferon inducers are retroviruses".
In 1991 American immunologist Elaine Defreitas had published her own discovery of retroviral gene sequences in 80 percent of adult and child ME sufferers and in 4 percent of controls. Unfortunately Defreitas had been "savaged and thrown to the wolves".
In defiance of protocol, they [the CDC] refused to follow her methods at every turn. Ignoring her proscription against freezing blood, scientists froze ME blood samples in order to take vacations. They employed chemical reagents Defreitas had warned against, they cast aside reagents she recommended, they regarded the ratios of particular nutrients Defreitas used to nurture her cell cultures (and the virus) as unimportant. Defreitas said "If a plague were to hit this country, the CDC would be the last to know".
After the CDC refused to send a scientist to Defreitas' lab to learn the right way, Mikovits said "The CDC is culpable. They let an entire generation become infected. I think they all know there's a huge class action lawsuit here".

Best site on XMRV with good links to videos and other sites: http://cfsandxmrv.blogspot.com