  We formulate a generalized susceptible exposed infectious recovered (SEIR)
model on a graph, describing the population dynamics of an open crowded place
with an arbitrary topology. As a sample calculation, we discuss three simple
cases, both analytically, and numerically, by means of a cellular automata
simulation of the individual dynamics in the system. As a result, we provide
the infection ratio in the system as a function of controllable parameters,
which allows for quantifying how acting on the human behavior may effectively
lower the disease spread throughout the system.
