The illness affects an estimated 1 percent of people worldwide and, as its name implies, involves crippling fatigue as well as aching joints, headaches and various other symptoms.
Recently, XMRV was detected in prostate cancer patients and in prostate tumor biopsies. Like other retroviruses, it can activate latent viruses in the body, such as Epstein-Barr, which has been linked to chronic fatigue syndrome.
For this study, researchers analyzed 101 blood samples taken from patients with chronic fatigue syndrome and found the virus in 68 of the samples, as compared with only eight samples in 218 healthy patients (67 percent versus 3.7 percent).
Although 3.7 percent seems a small proportion, the authors do note that this could mean millions of people are infected with a virus whose effects are as yet unknown.
Retroviruses, a group that includes both XMRV and HIV, have genomes made of RNA instead of DNA.
"When the virus infects cells, the RNA gets copied into the DNA, then the DNA inserts itself or integrates into the host DNA," explained Silverman. "One of the many problems with infections with retroviruses is that it's very difficult to actually cure the patient because the virus DNA becomes part of the infected person's DNA. Patients need to continually take drugs to keep it from replicating."
XMRV is simpler than HIV, though, Silverman added, which is a good thing. "It's a kind of stripped down version of a retrovirus. It has just the genes required for infection and replication. We could probably stop it with an antiretroviral drug."
There's also the possibility that a vaccine would prevent people from being infected in the first place.
But, stressed Silverman, "there are lots of qualifiers because it hasn't actually been proven that it causes disease, although the evidence looks pretty intriguing. This is an area that needs more research."
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