What's Up with Chronic Fatigue?

Here is some of the best drama you're going to see in science: two major studies are published six weeks apart and report exactly opposite results. Their subject? A squirrely syndrome that is anything from a devastating infectious disease to a made-up malaise, depending who you ask.

Chronic fatigue syndrome, or CFS, is (quick overview!) pretty much what it sounds like. Its trademark is a crippling exhaustion that lasts for months or years. There's no test or cure for CFS. Doctors first rule out every other possibility--such as hormonal problems, mental illnesses, sleep disorders, or lupus--before giving a diagnosis of CFS.

The syndrome jumped into headlines last year when Science published a paper announcing a correlation between CFS and a certain retrovirus called XMRV. A retrovirus is (quick overview!) a virus that cleverly inserts its own genes into your DNA, so your body keeps replicating it. HIV is one.

The authors of the paper found this retrovirus in 68 out of 101 patients with CFS, but in only 3.7% of healthy patients. This could mean that XMRV causes or contributes to chronic fatigue (but not in all patients). Or it could mean nothing: XMRV could be an unremarkable infection that easily takes hold in people who already have poor health.

Other researchers criticized the methods of the first study. Meanwhile, three other studies failed to find any link between chronic fatigue and XMRV. But all these studies were done in Europe; could XMRV only be responsible for chronic fatigue in the U.S.? Then, this July, an American study done by the CDC also failed to find any connection.

You might think that would be the final nail in the coffin for the virus theory. But wait! In August, another group of American researchers announced that they'd studied the blood of CFS patients and found--well, not XMRV. But they found gene sequences that come from a group of viruses related to XMRV.

So what's going on? The CDC suggests that chronic fatigue is "a common endpoint of disease resulting from multiple causes." Maybe a retrovirus is relevant to some percentage of CFS cases, or maybe it's not. A controversial researcher named Simon Wessely has proposed that whatever event triggers CFS is, ultimately, not as important as the behavioral and psychological patterns people fall into after the illness starts. That's not to say that chronic fatigue isn't real, but that it represents a kind of physical and mental rut the body gets into.

It would certainly be easier to treat CFS if it turned out that a virus or some other single factor was to blame. But given the way the research has swung back and forth, I wouldn't bet on anyone finding a magic bullet. Some CFS patients are eager to try antiretroviral drugs--the same ones used to treat HIV. But these drugs can have severe side effects. The editor of the journal that published the most recent study said that patients taking off-label antiretrovirals would be "a very bad consequence of this."

Stay tuned, because more research--and more drama--is sure to come.