  The COVID-19 pandemic has led to significant changes in how people are
currently living their lives. To determine how to best reduce the effects of
the pandemic and start reopening societies, governments have drawn insights
from mathematical models of the spread of infectious diseases. In this article,
we give an introduction to a family of mathematical models (called
"compartmental models") and discuss how the results of analyzing these models
influence government policies and human behavior, such as encouraging mask
wearing and physical distancing to help slow the spread of the disease.
