ABSTRACT
EBV infection may have a wide range of clinical consequences: it is often asymptomatic; some cases-generally adolescents-develop the classic "infectious mononucleosis" syndrome; in rare cases the illness takes a severe, fatal course. EBV is also implicated in some geographic areas, in Burkitt' lymphoma and naso-pharyngeal carcinoma. Recent research has enrich our knowledge on the viral genome and the various viral antigen, but some problems are still unsolved. The "normal" immunological response to EBV infection is briefly summarized; then the abnormal immunological pattern is considered in relation to some conditions such as age, congenital and acquired immunodeficiencies and unusual clinical syndromes. Recently a group of not well defined, persistent illnesses (fever, fatigue, headache etc.) has been correlate to a "chronic" EBV infection. It becomes more and more evident that different clinical manifestations of EBV infection are always connected with a particular immunological response; between the "normal" cases and those with well defined immunodeficiency probably large group exists in which minor immunological abnormalities are responsible for a partial derepression of the virus.
