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Chronic fatigue syndrome caused by virus? What new study says

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(CBS/AP) Are scientists back to square one with chronic fatigue syndrome?

New research suggests that a virus - called XMRV - once thought to be linked to the syndrome in a 2009 study may have been a false alarm.

Scientists looked at the same patients from the earlier study, and couldn't find any evidence XMRV in their blood samples. The new study - published in the September 22 issue of Science - concluded lab tests used to make that original link were unreliable.

"The original findings that led to the concern and the excitement that this is real aren't reproducible," study author Dr. Michael P. Busch, professor of laboratory medicine at the University of California at San Francisco and director of the Blood Systems Research Institute, told WebMD. "I take that as an indication that those results are unreliable," he said.

The purported link dates back to a study - also published in Science - in which Nevada researchers announced they'd found the mouse-related XMRV infection the blood of chronic fatigue patients, fueling hopes that a cause for the mysterious illness had finally been found. Blood banks soon started turning away donations from people with chronic fatigue.

Yet numerous studies have since failed to confirm the findings. Last spring, Science declared any link between the infection and chronic fatigue in "seriously in question."

The newest study was part of government efforts to see if XMRV or related viruses might affect the safety of the blood supply. It concluded there's no reason to worry.

For the study, nine laboratories re-tested blood samples from 30 people, some healthy, and some chronic fatigue patients previously reported to have XMRV. Only two of the labs that previously reported the virus in blood samples could find any signs of the virus for the new tests - but some of those samples were from healthy people, and additional testing couldn't confirm the findings.

But researchers at Whittemore Peterson Institute in Nevada, who worked on the original research, still stand behind their results despite partially retracting some, so this controversy won't soon let up.

"All this study really says is that we can't detect it in the blood reproducibly," Dr. Judy A. Mikovits, director of research at the Whittemore Peterson Institute, told WebMD. "There's no data in this study or any other to support that. Clearly things aren't over or they wouldn't be awarding grants for people like us to study this virus."

As its name suggests, chronic fatigue syndrome causes extreme exhaustion that is not relieved by rest, along with flu-like symptoms including muscle aches and headaches. There is currently no treatment, but many people with the syndrome also have depression, so therapy and antidepressant medications sometimes help.

The CDC has more on chronic fatigue syndrome.