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Cases were defined as persons who had:(1)severe persistent fatigue following an acute illness appearing in an individual with no previous physical or psychological symptoms;(2)presenting signs and symptoms of an acute infection;(3)severe and persistent headache and/or myalgias;and(4) abrupt change in cognitive function or the appearance of a new mood disorder.After three years of follow up,almost all study subjects were able to return to preillness activity.None of the viruses evaluated-human T-lymphotrophic viruses I and II,Epstein-Barr virus,or human herpesvirus- 6-could be etiologically linked to these outbreaks.Clinical features of outbreaks of chronic fatigue syndrome differ sufficiently to suggest different etiologic agents.Giardiasis appears to have precipitated one of the four clusters in this study but the cause(s)of the other three outbreaks is as yet uncertain.The overall prognosis of chronic fatigue syndrome is usually favorable. |
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