It is controversial whether viruses are alive, but – like all living things – they do evolve. This fact has become abundantly clear during the pandemic, as new variants of concern have emerged every few months.
Some of these variants have been better at spreading from person to person, eventually becoming dominant as they out-compete slower versions of SARS-CoV-2, the virus that causes COVID-19. This improved spreading ability has been ascribed to mutations in the spike protein – the mushroom-shaped projections on the surface of the virus – that allow it to bind more strongly to ACE2 receptors. ACE2 are receptors on the surface of our cells, such as those that line our airways, that the virus attaches to in order to gain entry and start replicating.
