Update (Janyary 2012): Two studies identifying XMRV in CFS patients have been retracted, including the original paper that proposed the association. The current, best supported evidence, in this area suggests that the association was actually due to contamination. There appears to be strong scientific agreement that CFS is not related to infection with this virus.

Contributed by Guest Blogger: Nicole Krenitsky ’11

Patients with Chronic Fatigue Syndrome (CFS) perked up when a paper published in Science in 2009 linked the symptom-defined illness to xenotropic murine leukemia virus-related virus (XMRV). XMRV, also connected to prostate cancer, is positive sense, single-stranded RNA retrovirus of the class murine leukemia viruses (MLV). Four subsequent studies failed to find any MLV-related viruses in CFS patients or controls. Then in 2010, a paper published in PNAS reinvigorated the debate. The study did not specifically find XMRV but did find MLV-related viruses in the blood cells of CFS patients tested. Yet one month later, the CDC published report, stating that they had not found any MLV-related viruses in their own study of CFS patients.

Reasons for the inconsistent results are presently unknown. One hypothesis is that the PCR could have picked up mouse DNA or mouse viruses, contaminating the tests and producing false positives. Another involves the samples of participants; CFS is diagnosed solely based on symptoms and clinical case definitions such as the one published by the CDC do not differentiate well between CFS and depression, resulting in overdiagnosis. A study conducted by Ian Lipkin is underway and seeks to standardize sampling and analysis methods and use a larger sample size to settle the controversy.

Relating CFS to a virus has far-reaching consequences for patients and for public health. Antiretrovirals used to treat HIV have been shown to inhibit XMRV replication in vitro and some CFS patients have already begun ART following the 2009 Science publication. The AABB and the American Red Cross, erring on the side of caution, have banned patients with CFS from donating blood erring on the side of caution. If CFS is caused by MLV-related viruses, the blood supply would be tainted the syndrome passed to transfusion recipients.

One million Americans are affected by CFS and experience sleep disorders, cognitive difficulties, chronic muscle pain and headaches. Many dismiss the disorder as psychosomatic and doubt its legitimacy as an illness. In addition to diagnostic testing and finding clinical treatment or a cure for CFS, a link to a virus would give CFS scientific credibility. Mary Schweitzer, historian and CFS sufferer explains, “Patients are hopeful that now the disease itself might be treated seriously, that they’ll be treated seriously, and that there might be some solution.”