Epidemic neuromyasthenia and chronic fatigue syndrome in west Otago, New Zealand. A 10-year follow-up.
BACKGROUND: In 1984, an outbreak of an illness characterized by prolonged unexplained fatigue was reported in West Otago, New Zealand. This outbreak resembled other reported outbreaks of epidemic neuromyasthenia in that affected individuals presented with a spectrum of complaints ranging from transient diarrhea and upper respiratory disorders to chronic fatigue syndrome (CFS). OBJECTIVE: To obtain a perspective on the natural history of CFS not possible in clinic-based studies. METHODS: Twenty-three of the 28 patients in the original report were contacted and asked to complete written questionnaires. Interviews were obtained in person or via telephone. RESULTS: Ten (48%) of the 21 patients with satisfactory interviews appeared to meet the current Centers for Disease Control and Prevention (CDC) case definition of CFS, and 11 were classified as having prolonged or idiopathic fatigue. A return to premorbid activity was seen in most (n = 16) patients, although some reported the need to modify their lifestyle to prevent relapses. A female predominance was noted in those meeting the CDC case definition for CFS, whereas males predominated in patients diagnosed as having prolonged or idiopathic fatigue. CONCLUSIONS: The high proportion of patients recovering from CFS in the West Otago cluster suggests that epidemic-associated CFS has a better prognosis than sporadic cases. Female sex was confirmed as an important risk factor for CFS.