1921-1987 africa burkittlymphoma cancer carcinogenesis celldifferentiation celltransformation charlotte congresses contamination etiology friend friendvirus governmentpolicy hematopoieticstemcells hepatitisbvirus kaposi leukemia liverneoplasms medicaloncology nasopharyngealneoplasms neoplasmproteins neoplasms neoplastic oncogenes oncogenicviruses pathogenicity penileneoplasms poliomyelitisvaccine sarcoma sv40(virus) tumorantigens unitedstates uterinecervicalneoplasms viral viralcelltransformation