A NOTE ON THE BACKWARD BIFURCATION PHENOMENON IN A TUBERCULOSIS MATHEMATICAL MODEL

پوختە

This work investigates the existence of the backward bifurcation phenomenon in a mathematical model designed to simulate hyperendemic TB in the Asia-Pacific (James et al [7℄). It is shown that the possibility of the backward bifurcation is determined by the loss of partial immunity to TB, immunity conferred due to the administration of the BCG vaccine and recovery from a previous infection due to treatment. The existence of the backward bifurcation in the system has a very strong implication for disease control as the likelihood of a stable high endemic level is possible even when the epidemiological parameters are in-dicative of feasible control strategies that normally should lead to disease eradication when the control reproduction number of the model is used as a tool for designing public health control policies.