SARS-CoV-2 virulence evolution: avirulence theory, immunity, and trade-offs

The COVID-19 pandemic has led to a resurgence of the debate on whether host-parasite interactions should evolve towards avirulence. In this review, we first show that SARS-CoV-2 virulence is evolving, before explaining why this virus could be expected to follow the same evolutionary trajectory as other human seasonal coronaviruses. Leaning on existing theory, we then discuss hypotheses explaining why the virulence has increased since the beginning of the pandemic. Finally, we mention some potential scenarios for the future.