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Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài:Assessing the effects of multiple infections and long latency in the dynamics of tuberculosis. | Yang and Raimundo Theoretical Biology and Medical Modelling 2010 7 41 http www.tbiomed.eom content 7 1 41 THEORETICAL BIOLOGY AND MEDICAL MODELLING RESEARCH Open Access Assessing the effects of multiple infections and long latency in the dynamics of tuberculosis Hyun M Yang1 Silvia M Raimundo2 Correspondence hyunyang@ime. unicamp.br 1UNICAMP-IMECC. Departamento de Matemática Aplicada Prapa Sérgio Buarque de Holanda 651 CEpP 13083-859 Campinas SP Brazil 2 BioMed Central Abstract In order to achieve a better understanding of multiple infections and long latency in the dynamics of Mycobacterium tuberculosis infection we analyze a simple model. Since backward bifurcation is well documented in the literature with respect to the model we are considering our aim is to illustrate this behavior in terms of the range of variations of the model s parameters. We show that backward bifurcation disappears and forward bifurcation occurs if a the latent period is shortened below a critical value and b the rates of super-infection and re-infection are decreased. This result shows that among immunosuppressed individuals super-infection and or changes in the latent period could act to facilitate the onset of tuberculosis. When we decrease the incubation period below the critical value we obtain the curve of the incidence of tuberculosis following forward bifurcation however this curve envelops that obtained from the backward bifurcation diagram. Background Infectious diseases in humans can be transmitted from an infectious individual to a susceptible individual directly as in childhood infectious diseases and many bacterial infections such as tuberculosis or by sexual contact as in the case of HIV human immunodeficiency virus . They can also be transmitted indirectly by vectors as in dengue and intermediate hosts as in schistosomiasis . According to the natural history of diseases an incubation period followed by an infectious period has to be considered a common characteristic. .
