The American Red Cross announced Friday that it was barring people with chronic fatigue syndrome from donating blood to reduce the risk of transmitting a virus that has been associated with the disease.
The virus is known as xenotropic murine leukemia virus-related virus, or XMRV. Some studies have found that people with chronic fatigue syndrome are more likely to carry the virus. But it remains far from clear whether the virus causes the disease.
Nevertheless, the Red Cross decided to bar people with the syndrome from donating "in the interest of patient and donor safety," according to an announcement from the organization.
Between 1 million and 4 million Americans are thought to have the syndrome, which causes prolonged and severe fatigue, body aches and other symptoms.
The step comes after new research strengthened the possible connection to the virus.