Chronic fatigue syndrome is a controversial condition, conflicts about which have frequently burst out of the medical literature into the popular media. Whilst these controversies may initially seem to be of limited interest to those who do not routinely treat such patients, they also exemplify important current issues in medicine. These issues include the nature of symptom-defined illness; patient power versus medical authority; and the uncomfortable but important issues of psychological iatrogenesis. The subject is therefore of relevance to all doctors. Fatigue is a subjective feeling of weariness, lack of energy, and exhaustion. Approximately 20 per cent of the general population report significant and persistent fatigue, although relatively few of these people regard themselves as ill and only a small minority seek a medical opinion. Even so, fatigue is a common clinical presentation in primary care. When fatigue becomes chronic and associated with disability it is regarded as an illness. Such a syndrome has been recognized at least since the latter half of the last century. Whilst during the Victorian era patients who went to see doctors with this illness often received a diagnosis of neurasthenia, a condition ascribed to the effect of the stresses of modern life on the human nervous system the popularity of this diagnosis waned and by the mid-twentieth century it was rarely diagnosed (although the diagnosis subsequently became popular in the Far East—see Chapter 5.2.1). Although it is possible that the prevalence of chronic fatigue had waned in the population, it is more likely that patients who presented in this way were being given alternative diagnoses. These were mainly the new psychiatric syndromes of depression and anxiety, but also other labels indicating more direct physical explanations, such as chronic brucellosis, spontaneous hypoglycaemia, and latterly chronic Epstein–Barr virus infection. As well as these sporadic cases of fatiguing illness, epidemics of similar illnesses have been occasionally reported. One which occurred among staff at the Royal Free Hospital, London in 1955 gave rise to the term myalgic encephalomyelitis (ME), although it should be emphasized that the nature and symptoms of that outbreak are dissimilar to the majority of those now presenting to general practitioners under the same label. A group of virologists and immunologists proposed the term chronic fatigue syndrome in the late 1980s. This new and aetiologically neutral term was chosen because it was increasingly recognized that many cases of fatigue were often not readily explained either by medical conditions such as Epstein–Barr virus infection or by obvious depression and anxiety disorders. Chronic fatigue syndrome has remained the most commonly used term by researchers. The issue of the name is still not completely resolved however: Neurasthenia remains in the ICD-10 psychiatric classification as a fatigue syndrome unexplained by depressive or anxiety disorder, whilst the equivalent in DSM-IV is undifferentiated somatoform disorder. Myalgic encephalomyelitis or (encephalopathy) is in the neurological section of ICD-10 and is used by some to imply that the illness is neurological as opposed to a psychiatric one. Unfortunately the case descriptions under these different labels make it clear that they all reflect similar symptomatic presentations, adding to confusion. Official UK documents have increasingly adopted the uneasy and probably ultimately unsatisfactory compromise term CFS/ME. In this chapter, we will use the simple term chronic fatigue syndrome (CFS).
Cytomegalovirus and Epstein-Barr Virus Infection as a Cause of Chronic Fatigue Syndrome in Travelers to Tropical Countries
