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Scientists now doubt studies linking chronic fatigue syndrome to mouse virus

(CBS/AP) Doctors who continue to believe that chronic fatigue syndrome is caused by a mysterious mouse virus may need to wake up and smell the coffee. New studies suggest that previous research purporting such a link was a false alarm.

In 2009, researchers in Nevada and Maryland said they had linked chronic fatigue to the so-called XMRV virus, which causes illness in mice. The announcement made headlines and fueled hopes that a cause had finally been found for chronic fatigue syndrome, an illness that affects about 1 million Americans.

But two new studies suggest the purported link between the XMRV virus and chronic fatigue syndrome may have been simply the result of laboratory contamination. On Tuesday, the journal "Science" took the unusual step of declaring the XMRV link "seriously in question."

In a separate study, yet another team of researchers tested blood from the same chronic fatigue patients used to make that first 2009 link with XMRV. This new testing, which avoided using lab products derived from mice, found no evidence XMRV, further supporting the lab-contamination explanation. In any case, substances in human blood are able to kill the mouse-related virus, said lead researcher Dr. Jay Levy of the University of California, San Francisco.

The National Institutes of Health has begun other studies to settle the issue, but Dr. Levy said it's time to give it a rest and focus on other causes. "Let's use the money to find the real culprit," he said.

Researchers at Nevada's Whittemore Peterson Institute, who first reported a possible XMRV link, didn't immediately comment Tuesday.

Chronic fatigue syndrome is characterized by overwhelming fatigue for at least six months despite ample rest. The condition also causes weakness, muscle pain, impaired memory and/or mental concentration, and insomnia. Chronic fatigue syndrome can't be diagnosed with a simple test, so scientists diagnose by excluding other disease-causing factors. Women between the ages of 40 and 50 years old are most frequently diagnosed with the disease.

The CDC has more on chronic fatigue syndrome.

Ryan Jaslow

Ryan Jaslow is's health editor.

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