Post-viral fatigue syndrome. Epidemiology: a critical review.

Numerous reports in medical journals, lay magazines, and newspapers bear witness to the level of interest in the postviral fatigue syndrome and the heated controversy about the true nature of this condition. For many, it represents a 'rag bag' diagnosis into which unsolved diagnostic problems are discarded. Others are in no doubt that there is a discrete syndrome, probably with a specific causation. The real answer almost certainly lies somewhere in between, but the truth can only be established through epidemiological studies designed to answer key questions. Does it exist at all, and, if so, how frequently does it occur? Who is most likely to get it and what is its cause? What is the nature of its implied association with viral infections and what is the role of other frequently postulated factors, such as psychiatric morbidity? What is its natural history and is there any evidence that any of the treatment/management regimes on offer can effectively lead to symptomatic relief or improve prognosis? In this chapter, we consider the evidence on these key questions, identify some of the deficiencies in our current knowledge and highlight the kind of research which is still required.