Chronic Fatigue Following Acute Epstein-Barr Virus Infection in Adolescents

Chronic fatigue syndrome (CFS) is characterized by unexplained, disabling and long lasting fatigue, as well as pain, impaired memory, sleep difficulties and other symptoms. Epstein-Barr virus (EBV) infection might precipitate CFS. In this study, 200 adolescents undergoing acute EBV infection will be followed prospectively, and also compared with a group of healthy controls. The aim is twofold: * To identify factors that predispose to chronic fatigue among adolescents with acute EBV infection * To compare pathophysiological features of patients with acute EBV infection with a group of healthy controls. Possible risk factors for chronic fatigue 6 months after EBV-infection includes: * Severity of the initial infection * Immune responses characteristics * Characteristics of the neuroendocrine stress response * Cognitive functioning * Emotional disturbances * Genetics/ epigenetics of candidate genes * Certain personality traits * Critical life events