herpesviiruste rühma kuuluv suuremõõtmeline DNA‑viirus, mille kandjateks on peaaegu kõik täiskasvanud inimesed, tähtsaim mononukleoosi tekitaja, a herpes virus which is the major cause of infectious mononucleosis and a common subclinical illness in children and young adults which is characterized by seroconversion to the virus, and which is as, a herpesvirus (species Human herpesvirus 4 of the genus Lymphocryptovirus) that causes infectious mononucleosis and is associated with Burkitt's lymphoma and nasopharyngeal carcinoma