Endemic equilibrium of the susceptible-infective model with exponential birth (source code)

= Endemic equilibrium of the susceptible-infective model with exponential birth

When the disease-free equilibrium is unstable, the positive equilibrium satisfies
$$
S^*=\frac{d+\delta}{\beta},
\qquad
\beta I^*+d=be^{-aS^*}.
$$
Its Jacobian has negative trace and positive determinant, so the equilibrium is locally asymptotically stable.