Viral cause for chronic fatigue?

“Either [the virus] is a causative factor or it’s a marker of patients who cannot clear the virus,” Eugene Kandel, a molecular biologist at Roswell Park Cancer Center who was not involved in the study, told The Scientist. The study doesn’t distinguish between the two possibilities, he said. The virus, awkwardly named xenotropic murine leukemia virus-related virus (XMRV), may simply be a passenger, more prevalent in patients with underlying disease.

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Here, the researchers found XMRV in 67% of samples from patients with chronic fatigue syndrome out of 101 samples analyzed, compared to approximately 4% of 218 control samples. Researchers also found antibodies to XMRV in the serum of the infected patients, suggesting that patients mounted a specific immune response to the virus.

XMRV, a retrovirus with close homology to the cancer-causing mouse virus, murine leukemia virus (MLV), was first discovered in 2006 by researchers tracking down an enzyme that was mutated in prostate cancer patients. The enzyme had both tumor suppressor and antiviral properties, which suggested the possibility that prostate cancer had an infectious cause. When researchers scanned tissue from prostate cancer patients for viral infection using a specially-designed virus chip, they pinpointed XMRV.