Chronic fatigue syndrome (CFS) is one of those nebulous diseases that’s really more of a diagnosis of exclusion than anything else. As the name suggests, it’s characterized by overwhelming fatigue–often so much so that patients can barely get out of bed–as well as a number of non-specific symptoms, including weakness, muscle pain, and insomnia. Currently, there is no diagnostic test for the disease, and the cause(s) is (are) unknown. Indeed, it should be noted that there’s disagreement over even the most basic assumption that such a thing as CFS exists, or whether it’s merely psychosomatic. However, a number of lines of evidence (including high antibody titers in many patients) point to an infectious agent as at least a co-factor in the development of the illness, and the Epstein-Barr virus (EBV, which also causes infectious mononucleosis) has been frequently pointed to as a possible causative agent. (Another common herpes virus, HHV-6, has also been investigated as a cause). However, the epidemiology of EBV has made it difficult to study this potential connection using traditional study designs. More on this after the jump.
EBV is a member of the herpesvirus family. Like many herpes viruses, EBV is extremely common; it’s estimated that almost all of us have been infected by the age of 40. This makes it difficult to employ a typical study used in epidemiology: the case-control study. In this example, we could look at the presence of antibodies against EBV in the blood of those diagnosed with CFS versus healthy controls. The problem with this is that such a large number of the controls will also have EBV antibodies, it’s much more difficult to tease out differences between the two populations. Investigators have, however, looked at the amount of antibodies present, and have found (in some papers) that those diagnosed with CFS tend to have higher anti-EBV antibodies than healthy controls. (However, some publications have found no such connection). This could also be due to the fact that, as I mentioned, CFS is a disease of exclusion–if you have the symptoms of CFS, and don’t have any of the other common causes of long-term fatigue*, then you get lumped into the CFS group. The problem, from an epidemiological standpoint, comes in if CFS isn’t just due to one cause–what if it’s due to multiple causes, or even multiple viruses?
This is much more difficult to sort out, but some researchers are going ahead and testing the first, and more basic, premise: might CFS be caused by a virus? They’ve done this by treating CFS patients with antiviral regimines:
Montoya now has data on 25 CFS patients, nearly all of whom had high levels in their blood plasma of antibodies to the human herpes virus 6 (HHV-6) and the Epstein-Barr virus. The data — presented recently at a conference in Fort Lauderdale, Florida — were remarkably consistent. Nearly every patient responded to the drug, Montoya said, and most of the responses were dramatic.
Last year [CFS sufferer Michael] Manson began a six-month course of Valcyte, which is approved to treat transplant patients to prevent viral infection. At first he felt worse. Then, after a few weeks, he began to improve. He started walking, every day a little more.
The research was presented at a conference and so hasn’t yet been published in a journal. It’s noted in the article that this was a small trial–only 25 people–and so before anyone gets too excited, the results need to be replicated in larger studies. Additionally, by the results they describe in here alone, we can’t be sure that the improvement is actually due to decreasing the amount of virus present, or due to some other affect of the antiviral drug. Finally, even if the antivirals are killing a particular virus, at this point we still don’t know which one that would be, or indeed, if it is only one.
All in all, an interesting tidbit of information, but I’m concerned that the small size of the study and the preliminary nature of the results will get downplayed. Many CFS sufferers feel like they’ve been left behind and ignored by moden medicine, and many are convinced that curing them is as easy as ridding them of whatever mysterious virus lurks in their body. This may be the case, and if larger controlled trials and additional bench research confirm these findings, great. Potentially, this could even help us find a cause (or causes) of the illness–but we’re still a long way off from that right now. I just hope patient advocates temper their enthusiasm and wait for more science to confirm these findings.
*(which, according to the CDC website, include hypothyroidism, sleep apnea and narcolepsy, major depressive disorders, chronic mononucleosis, bipolar affective disorders, schizophrenia, eating disorders, cancer, autoimmune disease, hormonal disorders, subacute infections, obesity, alcohol or substance abuse, and reactions to prescribed medications)