“…Since the bifurcation coefficient b is positive, it follows from Theorem 4.1 in [6] that the model (1), or the transformed model (8), will undergo a backward bifurcation if the backward bifurcation coefficient, a, given by (11) is positive. Setting the HPV and TB re-infection paramters ϕp = 0, σt = 0 and the TB exogenous re-infection term ε t 1 = 0, the bifurcation coefficient, a < 0 (since (1 − ξ t 2 )ν8 > ξ t 2 ν9 > 0 and (1 − ξ t 3 )ν10 > ξ t 3 ν11 > 0, based on the definition of the components in (9), and also noting that all other components of the left and right eigenvectors occuring in the coefficient, a, are positive, including the parameters of the model. Hence, backward bifurcation does not occur in the Oncogenic HPV-TB co-infection model, in the absence of HPV and TB re-infection and in the absence of exogenous re-infection.…”