Fig 5. Plots of f(T**) against T** where T** is the equilibrium value of infected cells.

The parameters used were β₂ = 0.0000024 for Fig 5 a and β₂ = 0.024 for Fig 5 b. The graph does not cross the zero line for small values of β₂ and crosses the zero line for large values of β₂ and thus there is no solution for small values of the transmission parameter. Existence of the disease equilibrium depends on the rate at which cells are infected. f(T**) is given in Eq 19.