  In this paper we study a discrete-time SIS (susceptible-infected-susceptible)
model, where the infection and healing parameters and the underlying network
may change over time. We provide conditions for the model to be well-defined
and study its stability. For systems with homogeneous infection rates over
symmetric graphs,we provide a sufficient condition for global exponential
stability (GES) of the healthy state, that is, where the virus is eradicated.
For systems with heterogeneous virus spread over directed graphs, provided that
the variation is not too fast, a sufficient condition for GES of the healthy
state is established.
