Evidence for an etiologic relation of the Epstein-Barr virus to human malignancies.

Studies on virus-induced animal tumors have provided indirect approaches to a search for viruses causing human malignancies. Epstein-Barr virus (EBV), the cause of infectious mononucleosis, served to illustrate the usefulness of these approaches in linking EBV with Burkitt's lymphoma and nasopharyngeal carcinoma. Despite its demonstrated intimate association with these tumors the role of EBV in their causation remains uncertain. While a passenger role seems excluded, it cannot be decided whether EBV is the primary or a secondary agent in the etiology of the tumors. If the primary cause, immunologic, genetic, virologic or other environmental factors are undoubtedly needed for EBV to express its obvious oncogenic potential. The data illustrate the difficulties encountered in proving a viral etiology of human malignancies.