Abstract

The aim of this report is to review the relationship between viruses and the development of human cancer. It is currently known at least four viruses are directly implicated in the aetiology of human cancers and are involved in the induction of 15 to 20% of the worldwide tumor burden. Infection with these viruses seems to be an essential, but not sufficient, step in the multistage proces of carcinogenesis. Other changes, induced for instance by chemical carcinogens or radiation, are also required to change the virus infected cell into a tumor cell. The four most important human tumor viruses are: human T cell leukemia viruses (HTLV); Epstein-Barr virus (EBV); hepatitis B virus (HBV) and human papillomavirus (HPV). Because of HPV is probably involved in the development of over 10% of all human tumors and hence is the most important biological agent in relation to cancer, it is discussed more extensively in this report.