  We revisit the SICA (Susceptible-Infectious-Chronic-AIDS) mathematical model
for transmission dynamics of the human immunodeficiency virus (HIV) with
varying population size in a homogeneously mixing population. We consider SICA
models given by systems of ordinary differential equations and some
generalizations given by systems with fractional and stochastic differential
operators. Local and global stability results are proved for deterministic,
fractional, and stochastic-type SICA models. Two case studies, in Cape Verde
and Morocco, are investigated.
