To understand the origin of the Wuh

To understand the origin of the Wuhan CoV and its genetic relationship with other coronaviruses, we performed phylo- genetic analysis on the collection of coronavirus sequences from various sources. The results showed the Wuhan CoVs were clustered together in the phylogenetic tree, which be- long to the Betacoronavirus genera (Figure 1A). Betacor- onavirus is enveloped, single-stranded RNA virus that infects wild animals, herds and humans, resulting in occasional outbreaks and more often infections without apparent symptoms. The Wuhan CoV cluster is situated with the groups of SARS/SARS-like coronaviruses, with bat cor- onavirus HKU9-1 as the immediate outgroup. Its inner joint neighbors are SARS or SARS-like coronaviruses, including the human-infecting ones (Figure 1A, marked with red star). Most of the inner joint neighbors and the outgroups were found in various bats as natural hosts, e.g., bat coronaviruses HKU9-1 and HKU3-1 in Rousettus bats and bat coronavirus HKU5-1 in Pipistrellus bats. Thus, bats being the native host of the Wuhan CoV would be the logical and convenient reasoning, though it remains likely there was intermediate host(s) in the transmission cascade from bats to humans. Based on the unique phylogenetic position of the Wuhan CoVs, it is likely that they share with the SARS/SARS-like coronaviruses, a common ancestor that resembles the bat coronavirus HKU9-1. However, frequent recombination events during their evolution may blur their path, evidenced by patches of high-homologous sequences between their genomes (Figure S1B in Supporting Information).