American researchers have identified an unusual link between prostate cancer and chronic fatigue syndrome (CFS): An infectious virus known as xenotropic murine leukemia virus-related virus (XMRV) found in 68 out of 101 CFS patients. Also, XMRV was identified in eight out of 218 healthy patients (nearly 4 percent), suggesting millions of Americans may be carrying this virus unknowingly.

Even more alarming, scientists have found XMRV in 98 percent of 300 more CFS patients they have studied since the report was published.

XMRV is related to a retrovirus that's now part of the mouse genome, but is unable to infect mice cells. The virus can infect human cells easily, however. It's very possible, scientists say, XMRV may merely be a passenger virus that infects patients whose immune systems are compromised by CFS.

What's also known is that XMRV has been detected in prostate cancer patients who possess a genetic mutation that disables an important virus-fighting immune response. CFS patients, however, may have XMRV with or without this genetic marker.

The good news: This study may have proved CFS is an infectious disease, rather than a psychiatric one, says Dr. Judy Mikovits, the report's lead author. That's why scientists are forming plans to test antiretroviral drugs, including some used to treat HIV, to determine if they may treat CFS-related problems.

Science October 8, 2009

New York Times October 8, 2009

Reuters October 9, 2009

MedicineNet.com October 8, 2009

The Detroit News October 8, 2009