Timing and dynamics of repeated SARS-CoV-2 spillover events at the outset of the COVID-19 pandemic

Severe acute respiratory syndrome coronavirus 2 is responsible for a global pandemic causing more than 5 million deaths in the first two years since its detection at the Huanan Seafood Wholesale Market in December 2019 in Wuhan, China. As the original outbreak in Hubei Province spilled over to other countries, the diversity of SARS-CoV-2 quickly increased and led to multiple variants of concern, but the beginning of the pandemic was marked by two major lineages, A and B. This study aims to explore the evolutionary and epidemiological dynamics at the start of the pandemic.