Since the emergence of SARS-CoV-2 in Wuhan in 2019 its host reservoir has not been established. Phylogenetic analysis was performed on whole genome sequences (WGS) of 71 coronaviruses and a Breda virus.  A subset comprising two SARS-CoV-2 Wuhan viruses and 8 of the most closely related coronavirus sequences were used for host reservoir analysis using Bayesian Evolutionary Analysis Sampling Trees (BEAST). Within these genomes, 20 core genome fragments were combined into 2 groups each with similar clock rates (5.9x10 -3 and 1.1x10 -3 subs/site/year). Pooling the results from these fragment groups yielded a most recent common ancestor (MRCA) shared between SARS-COV-2 and the bat isolate RaTG13 around 2007 (95% HPD: 2003, 2011). Further, the host of the MRCA was most likely a bat (probability 0.64 - 0.87). Hence, the spillover into humans must have occurred at some point between 2007 and 2019 and bats may have been the most likely host reservoir.

Identification of the host reservoir of SARS-CoV-2 and determining when it spilled over into humans