Viruses and human neoplasia. Approaching etiology

The exotic and the mundane : Human immunodeficiency virus in Haiti

The HIV/AIDS epidemic in Haiti has often been referred to as a "mystery," and "striking similarities" between patterns of disease in Haiti and in sub-Saharan Africa are often underlined. The occurrence of AIDS in Haitians has also led to the postulation of a number of theories positing a Haitian origin for AIDS and linking the syndrome in Haitians to voodoo. A review of the epidemiological data gathered and published in the early years of the pandemic suggests that these "exotic" theories are not necessary to explain the Haitian epidemic, which is clearly linked not to Africa but to the United States. Patterns of risk identified among many of the first Haitians with AIDS are similar to risk factors identified in North America and Europe (same-sex contact with an HIV-infected individual and blood transfusion). The Haitian epidemicsubsequently came to resemble patterns seen in sub-Saharan Africa, where AIDS is predominantly a heterosexually transmitted disease. Similarly shifting patterns are described for several other Caribbean nations, underlining the importance of a historical analysis of the Caribbean pandemic as well as the necessity to link analysis of local epidemiology of AIDS/HIV to larger considerations of political economy.

Inflammation initiates cancer by depleting stem cells

According to the theory presented herewith, neoplasia results solely from stem cell depletion. Besides serving as tissue progenitors, stem cells are postulated to secrete a vital substance 'A' necessary for proper tissue function. Carcinogens interfere with 'A' production mainly by destroying stem cells and since the latter are not replenished, less 'A' is produced. In order to repair the deficiency, the organism grows a special organ, the neoplasm, dedicated to produce a substitute, denominated here as substance 'B'. Since carcinogens continue depleting stem cells, the neoplasm has to grow more and more in order to keep up with the demand, until reaching a stage of decompensation when the harm inflicted by it is greater than its benefit. Any stem cell depleting substance or process e.g. ablation, chemotherapy and inflammation, is regarded here as a carcinogen. Even animal tumor viruses are postulated here to exert their harm mainly by depleting stem cells. Protracted inflammation e.g. ulcerative colitis or cystic mastopathy, hits stem cells and is followed therefore by neoplasia. Age specific incidence rates of such pathologies resemble precursor-successor curves of tracer kinetics. The precursor inflammation hits young adults, while its successive neoplasia is more prevalent in older individuals. Although most age specific curves of adult cancers are unimodal, at least five are bimodal, resembling precursor-successor curves. These are: Hodgkin's disease, seminoma, nasopharyngeal and retroperitoneal tumors and cancer of bone and joints. It is suggested here that these age specific curves are mixtures of two pathologies, an inflammatory, which is prevalent in young persons, followed by neoplasia.