COVID-19 is a living example of Darwinian natural selection, and SARS-CoV-2 evolution is occurring under (and in) our noses.

This review explores COVID-19 (coronavirus disease of 2019) from the perspective of Darwinian natural selection and consequent evolution of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2). COVID-19 has caused unprecedented societal and economic turmoil. The human host population has responded with widespread vaccination, therapeutic monoclonal antibodies, convalescent plasma and antiviral drugs. SARS-CoV-2 has demonstrated remarkable resilience and has been able to quickly adapt to its rapidly changing habitat. SARS-CoV-2 has generated new antibody and vaccine evasive mutations in its genome, while simultaneously optimising its infectivity by improving its affinity to the ACE2 receptor and host proteases. Molecular analysis of SARS-CoV-2 has demonstrated natural selection of advantageous mutations in both individual patients with chronic COVID-19 infection and at a host population level, leading to extinction of less fit strains. COVID-19 is living proof of Darwinian evolution, which is occurring in observable time rather than over millions of years. Viewing COVID-19 from an evolutionary perspective will help mitigate the current and future pandemics. The aim of this article is to illustrate these concepts, using examples from the human host peer-reviewed literature.