  The current SARS-CoV-2 pandemic is a harsh reminder of the fact that, whether
in a single human host or a wave of infection across continents, viral dynamics
is often a story about the numbers. In this snapshot, our aim is to provide a
one-stop, curated graphical source for the key numbers that help us understand
the virus driving our current global crisis. The discussion is framed around
two broad themes: 1) the biology of the virus itself and 2) the characteristics
of the infection of a single human host. Our one-page summary provides the key
numbers pertaining to SARS-CoV-2, based mostly on peer-reviewed literature. The
numbers reported in summary format are substantiated by the annotated
references below. Readers are urged to remember that much uncertainty remains
and knowledge of this pandemic and the virus driving it is rapidly evolving. In
the paragraphs below we provide "back of the envelope" calculations that
exemplify the insights that can be gained from knowing some key numbers and
using quantitative logic. These calculations serve to improve our intuition
through sanity checks, but do not replace detailed epidemiological analysis.
