That doesn't mean the virus causes chronic fatigue, stressed the research published Thursday in the journal Science.
The team of scientists from the National Cancer Institute and Nevada's Whittemore Peterson Institute said it was possible the virus, named XMRV, was just "a passenger virus" that catches a ride in patients whose immune systems are weakened by chronic fatigue.
Moreover, the researchers found nearly 4 percent of healthy people carried the virus, too. That raises bigger questions about just what role this recently discovered virus -- a relative of viruses that cause cancer in mice -- may be playing in overall health.
"This suggests that several million Americans may be infected with a retrovirus of as-yet-unknown pathogenic potential," the researchers concluded.
A retrovirus is a kind of virus that permanently embeds in the body.
Various viruses have been linked to chronic fatigue over the years, only to fall by the wayside as potential culprits in the mysterious illness thought to afflict about 1 million Americans. It's characterized by at least six months of severe fatigue, impaired memory and other symptoms, but there's no test for it -- doctors rule out other possible causes -- and no specific treatment.
