At the time of diagnosis of MS in children, the earlier EBV infection had become latent and there was no serological sign of reactivation (IgM or anti-early antigen titres C80 as measured in an indirect immuno fluorescent assay) [12, 13] . Moreover, in adult patients, the MS-associated serological EBV pattern was probably established many years before the onset of clinically evident MS as prior infectious mononucleosis is a strong risk factor for MS manifesting 2-20 years (mean around 10-12 years) later [18, 25] . Taken together, these studies strongly indicate that latent EBV infection is an essential predisposing condition for the development of MS but other genetic, environmental and hygiene-related conditions appear necessary for the actual expression of the disease and the unifying condition might be a dysregulated immune response.