  We develop a macroscopic description of the evolutionary dynamics by
following the temporal dynamics of the total Shannon entropy of sequences,
denoted by $S$, and the average Hamming distance between them, denoted by $H$.
We argue that a biological system can persist in the so-called
quasi-equilibrium state for an extended period, characterized by strong
correlations between $S$ and $H$, before undergoing a phase transition to
another quasi-equilibrium state. To demonstrate the results, we conducted a
statistical analysis of SARS-CoV-2 data from the United Kingdom during the
period between March, 2020 and December, 2023. From a purely theoretical
perspective, this allows us to systematically study various types of phase
transitions described by a discontinuous change in the thermodynamic
parameters. From a more practical point of view, the analysis can be used, for
example, as an early warning system for pandemics.
