Summary: A recent paper [R. Xu
and Z. Ma
, Nonlinear Anal., Real World Appl. 10, No. 5, 3175–3189 (2009; Zbl 1183.34132
)] presents an
model of disease transmission with delay and nonlinear incidence. The analysis there only partially resolves the global stability of the endemic equilibrium for the case where the reproduction number
is greater than one. In the present paper, the global dynamics are fully determined for
by using a Lyapunov functional. It is shown that the endemic equilibrium is globally asymptotically stable whenever it exists.