Virus-associated lymphomas, leukaemias and immunodeficiencies in Africa.

The relationship between viruses and naturally occurring cancers, such as hepatocellular carcinoma and genital cancers, is of great importance to Africa. On the other hand, lymphomas, leukaemias and immunodeficiencies, although of less immediate public health importance, constitute an area of outstanding interest for research and their association with the Epstein-Barr virus (EBV) and the newly discovered human retroviruses merits world-wide attention. EBV-related malignancies in Africa include both Burkitt's lymphoma (BL) and nasopharyngeal carcinoma (NPC). Whether X-linked polyclonal lymphoproliferations exist in Africa remains an open question. The interrelationship between EBV, holoendemic malaria and genetic factors (oncogenes) has been deciphered in recent years, to make BL a kind of Rosetta stone for the understanding of multistage carcinogenesis. Although the role of EBV in the causation of NPC is not well understood, the viral capsid antigen (VCA) IgA test already allows both early detection of NPC in high-incidence areas and differential diagnosis in low-incidence areas. The question whether an EBV vaccine would be of value in African countries, in relation to EBV-associated malignancies, remains an open one. The diseases associated with the recently discovered human retroviruses (human T-lymphocyte leukaemia viruses: HTLVs) represent a new area for both research and public health assessment. Limited information is available today on the geographical distribution, age prevalence and association with disease in Africa of the different members of the retrovirus family (HTLV-1, HTLV-2, LAV/HTLV-3). The proportion of HTLV-related T-cell malignancies in different parts of Africa as well as the importance of immunodeficiencies caused by the different members of the retrovirus family remain to be determined. Typical acquired immunodeficiency syndrome (AIDS) appears to exist in Central Africa, especially Zaire, and HTLVs could be of public health importance if they cause severe forms of viral, bacterial or parasitic diseases through impairment of cell-mediated immunity. Africa, is and will long remain a continent of crucial importance with regard to the role of viruses in human malignancies and especially in haematopoietic proliferative disorders.