A virus called XMRC may be linked to chronic fatigue syndrome (CFS), a study shows.
The full name of the virus is xenotropic murine leukemia virus-related virus. It is part of a family of viruses known as murine leukemia viruses (MLV), which is a type of retrovirus known to cause cancer in mice.
The new study, published in the Proceedings of the National Academy of Sciences, conflicts with some earlier studies. Several U.S. studies, including a recent report from the CDC and research done in the U.K. and the Netherlands, found no evidence XMRV or other viruses in this family in the blood of people with CFS.
The new study shows that 86.5% of 37 people with CFS had evidence of this virus in their blood, as did 6.8% healthy blood donors. These findings back up a recent report by researchers at the Whitemore Peterson Institute in Reno, Nev., which showed similar results.
"There is a dramatic association with CFS, [but] we have not determined causality for this agent," said Harvey Alter, MD, chief of clinical studies and associate director for research in the department of transfusion medicine at the National Institutes of Health (NIH) Clinical Center in Bethesda, Md., at a news conference. "Other labs have not found this virus, so a dilemma at present is how to reconcile that some labs find the association and others do not."
"We think it is in the patient populations, not the lab testing [contamination causing a false-positive lab result], but the latter has not been completely ruled out," he says.
Steve Monroe, PhD, director of the division of high-consequence pathogens and pathology at the CDC, tells WebMD that the new study "raises as many questions as it answers and there are still a lot of things about this virus that we don't know."
Andrew L. Mason, an associate professor of medicine at the University of Alberta in Edmonton, Alberta, Canada, says it's time to act, not point fingers.
There have been several studies showing the presence of this virus in the blood of people with chronic fatigue syndrome and prostate cancer, but other studies have not found it.
"We don't know why that is," he says. "It is baffling, and we need to sort it out rather than ignore it. It's there. Does it cause disease? We don't know, but it's there and that needs to be investigated."
"There is only one way to prove or disprove XMRV's role and that is to do a proper study with antiviral drugs," Mason says. In an editorial accompanying the new study, he suggests studies that compare antiviral drugs with placebo or dummy pulls on viral load and CFS symptoms in affected individuals are now feasible.
