  We combine a pedestrian dynamics model with a contact tracing method to
simulate the initial spreading of a highly infectious airborne disease in a
confined environment. We focus on a medium size population (up to 1000 people)
with a small number of infectious people (1 or 2) and the rest of the people is
divided between immune and susceptible. We adopt a space-continuous model that
represents pedestrian dynamics by the forces acting on them, i.e. a microscopic
force-based model. Once discretized, the model results in a high-dimensional
system of second order ordinary differential equations. Before adding the
contact tracing to the pedestrian dynamics model, we calibrate the model
parameters, validate the model against empirical data, and show that pedestrian
self-organization into lanes can be captured. We consider an explicit approach
for contact tracing by introducing a sickness domain around a sick person. A
healthy but susceptible person who remains in the sickness domain for a certain
amount of time may get infected (with a prescribed probability) and become a
so-called secondary contact. As a concrete setting to simulate the onset of
disease spreading, we consider terminals in two US airports: Hobby Airport in
Houston and the Atlanta International Airport. We consider different scenarios
and we quantify the increase in average number of secondary contacts increases
as a given terminal becomes more densely populated, the percentage of immune
people decreases, the number of primary contacts increases, and areas of high
density (such as the boarding buses) are present.
