Infectious diseases have long been regarded as diseases of the South and chronic diseases as those of the North. With the globalization of exposures, climate change, and improvement in the control of transmissible diseases, these frontiers are becoming somewhat blurred.
With the lengthening of life-expectancy of HIV positive patients, linked to the use of effective anti-retroviral therapy, and the accompanying aging of the HIV positive populations, cancer became a noticeable cause of serious morbidity and mortality in the North. Studies in the South are still limited despite the fact that two-thirds of the world HIV positive population lives in sub-Saharan Africa.
Comparing results of studies on HIV and cancer from the South and the North, a pattern emerges. For Kaposi's sarcoma, non-Hodgkin lymphoma and cervical cancer, the association with HIV positivity, albeit remaining strong is weaker than the one found in the North. For non-AIDS classifying cancers, the directions of the associations are the same as in the North but detailed comparison of their magnitude is prevented by the paucity of data.
Potential explanations for these results include different background rates of the cancers in the South and the North (weaker association with higher background rates), as well as more frequent competing causes of death and later or missed diagnosis of cancer in the South. We propose a common physiopathological mechanism based on the role of immunity or lack thereof in cancer occurrence. The most likely candidate for this impaired immune background is the role in the South of infectious and tropical diseases. We thus suggest to investigate the association between a wide panel of biological agents and cancers, with evaluation of interaction with other carcinogenic behavioral and environmental exposures. This can only be done through a concerted effort of South and North epidemiologists, clinicians and biologists with complementary expertise.