[Epidemiology in the study of the role of viruses in human cancers].

An epidemiological approach is very useful in the study of the role of viruses in the development of human tumors, if properly integrated with the experimental approach and laboratory studies. Certain epidemiological characteristics of human tumours favour a viral etiology, e.g. space and time clustering, vertical and horizontal transmission of a tumour risk, succession in space or in time of viral induced benign lesions and of malignant tumours. In the framework of the association between the EB herpesvirus and both Burkitt's lymphoma and nasopharyngeal carcinoma, we conducted an epidemiological survey of the EBV infection in populations at different risk for EBV associated diseases. This survey showed that, in Uganda, the EBV infection was much earlier and heavier than in Hong Kong or Singapore. A hypothesis that early infection is related to BL risk is discussed as well as the value of epidemiology in both prospective studies and in prevention of virally induced tumours. The IARC prospective sero-epidemiological study on Burkitt's lymphoma and EBV in Uganda is given as an exemplar.