Tuberculosis, HIV and the developing world

This article reviews the immunology, genetics, epidemiology and treatment of two of the most important infectious diseases in the world, HIV and tuberculosis (TB). The pandemic of TB has been greatly magnified by the advent of the HIV epidemic. In the developing world, probably 50% of HIV seropositive individuals are co-infected with TB. The TB epidemic has expanded both because of increased susceptibility of patients to new tuberculous infection and also because of the greater chance of a primary complex leading to disseminated disease. The evidence that TB has had any effect on the HIV epidemic is less clear in the developed world with effective antiretroviral therapy. In resource-poor countries, many HIV infected individuals die prematurely of TB. Both organisms infect immunologically competent cells, and the control of infection in both has a large genetic component. The complex immunological response and process of cytokine release has a marked impact on both control of disease and the pathological effects of infection. Treatment of TB was associated with the development of resistance until the need for combination chemotherapy was recognised. It was then realised that one of the major factors making treatment of TB difficult was poor long-term adherence. Exactly the same sequence of events in terms of our understanding of the treatment of HIV infection has occurred more recently. These two infections undoubtedly present the most serious challenge to public health across the world, and are likely to be controlled only by a global mobilisation of resources not seen since the end of the last European war.