  In this study, we analyze the effectiveness of measures aimed at finding and
isolating infected individuals to contain epidemics like COVID-19, as the
suppression induced over the effective reproduction number. We develop a
mathematical model to compute the relative suppression of the effective
reproduction number of an epidemic that such measures produce. This outcome is
expressed as a function of a small set of parameters that describe the main
features of the epidemic and summarize the effectiveness of the isolation
measures. In particular, we focus on the impact when a fraction of the
population uses a mobile application for epidemic control. Finally, we apply
the model to COVID-19, providing several computations as examples, and a link
to a public repository to run custom calculations. These computations display
in a quantitative manner the importance of recognizing infected individuals
from symptoms and contact-tracing information, and isolating them as early as
possible. The computations also assess the impact of each variable on the
suppression of the epidemic.
