Cancer-Causing Virus Linked to Chronic Fatigue

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By AMY DOCKSER MARCUS

Researchers have linked an infectious virus known to cause cancer in animals to chronic-fatigue syndrome, a major discovery for sufferers of the condition and one that concerned scientists for its potential public-health implications.

An estimated 17 million people world-wide suffer from chronic-fatigue syndrome, and the Centers for Disease Control and Prevention puts the U.S. figure at between one million and four million. CFS is characterized by debilitating fatigue and chronic pain, but there are no specific treatments, and the diagnosis is often made by ruling out other diseases. Thus there is disagreement in the medical community as to whether CFS is a distinct disease. A study showing a strong viral association with CFS could change that equation.
[Researchers] Michael Hillerby, Whittemore Peterson Institute.

Researchers Judy Mikovits and Vincent Lombardi work in the lab at Whittemore Peterson Institute.

But the significance of the finding, published Thursday in Science, extends far beyond the community of people living with CFS. Researchers are just as concerned about the finding that nearly 4% of healthy people used as controls in the study were also infected with the virus, called XMRV. If larger studies confirm these numbers, it could mean that as many as 10 million people in the U.S. and hundreds of millions of people around the world are infected with a virus that is already strongly associated with at least two diseases.

The study was done by researchers at the Whittemore Peterson Institute for Neuro-Immune Disease in Reno, Nev., the National Cancer Institute and the Cleveland Clinic.

In September, researchers at the University of Utah and Columbia University Medical Center found XMRV in 27% of the prostate-cancer samples they examined. That study also showed that 6% of the benign prostate samples had XMRV. The chronic-fatigue study is the first to find live XMRV virus in humans.

Neither study conclusively shows that XMRV causes chronic-fatigue syndrome or prostate cancer. But the National Cancer Institute was sufficiently concerned to convene a closed-door workshop in July to discuss the public-health implications of XMRV infection. "NCI is responding like it did in the early days of HIV," says Stuart Le Grice, head of the Center of Excellence in HIV/AIDS and cancer virology at NCI and one of the organizers of the July workshop.

Like HIV, XMRV is a retrovirus, meaning once someone is infected, the virus permanently remains in the body; either a person's immune system keeps it under control or drugs are needed to treat it. The virus creates an underlying immune deficiency, which might make people vulnerable to a range of diseases, said Judy Mikovits of the Whittemore Peterson Institute and one of the lead authors on the paper.

So far, XMRV, known fully as xenotropic murine leukemia virus-related virus, doesn't appear to replicate as quickly as HIV does. Scientists also don't know how XMRV is transmitted, but the infection was found in patients' blood samples, raising the possibility that it could be transmitted through blood or bodily fluids.