The controversy surrounding the possible causes of chronic fatigue syndrome (CFS) resurfaced this month, after results published in the Archives of Paediatrics and Adolescent Medicine showed that children with the disease had higher levels of oxidative stress and white blood cell apoptosis than controls—findings suggesting that the children with CFS are fighting a viral infection.
The theory that CFS may be viral in origin first came to prominence in October, 2009, when a study in Science showed that 68 (67%) of 101 patients with CFS who were tested were infected with the murine leukaemia virus XMRV, compared with eight (37%) of 218 controls. A string of negative results followed, with several groups unable to detect any trace of XMRV in patients with CFS. But a study published recently in Proceedings of the National Academy of Sciences reported a strong association between CFS and a murine virus very similar to XMRV. However, it is impossible to say at this stage whether these murine leukaemia viruses cause CFS, or whether they are bystander infections.
It is already established that many cases of CFS are preceded by an acute viral infection. Studies in cohorts of patients with infectious mononucleosis caused by Epstein–Barr virus (EBV) show that a small proportion do not recover from post-infection fatigue, and subsequently go on to develop CFS. But it seems unlikely that CFS is a consequence of EBV, because most people make a full recovery.
There is a general consensus that CFS is a heterogeneous family of disorders, and it seems most likely that these disorders arise from a constellation of pathophysiological causes. The results in the Archives of Paediatrics and Adolescent Medicine received great media attention. But they do not prove that CFS is a physical disease. CFS is still far from being a well-defined entity. When the totality of available evidence is considered, the uncertainty around our understanding of the physical–psychological interaction taking place in patients with CFS only strengthens the case for giving research into chronic fatigue the high priority it deserves.
