Coronaviruses (CoVs) belong to the subfamily Othocoronavirinae, in the family Coronaviridae of the order Nidovirales. According to the 10th Report on Virus Taxonomy from the International Committee on Taxonomy of Viruses (ICTV), the Othocoronavirinae is comprised of four genera, including alphacoronavirus (alpha-CoV), betacoronavirus (beta-CoV), gammacoronavirus (gamma-CoV), and deltacoronavirus (delta-CoV) (King et al., 2018). Alpha- and beta-CoVs can infect mammals, including but not limited to bats, pigs, cats, mice, and humans (Kusanagi et al., 1992; Li et al., 2005b; Poon et al., 2005; Drexler et al., 2014; Pedersen, 2014; Kudelova et al., 2015; Cui et al., 2019). Gamma- and delta-CoVs usually infect birds, while some of them could infect mammals (Woo et al., 2009a, 2012, 2014; Ma et al., 2015). Since the late sixties, CoVs have been recognized as one of the viral sources responsible for the common cold. Among all CoVs identified so far, seven have the ability to infect humans, including human coronavirus 229E (HCoV-229E) and human coronavirus NL63 (HCoV-NL63), which belong to alpha-CoVs (Hamre and Procknow, 1966; Chiu et al., 2005), as well as human coronavirus OC43 (HCoV-OC43), human coronavirus HKU1 (HCoV-HKU1), severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and the newly emerged coronavirus (2019-nCoV), which are known to be beta-CoVs (Drosten et al., 2003; Ksiazek et al., 2003; Vabret et al., 2003; Woo et al., 2005; Zaki et al., 2012; Du et al., 2016b; Zhang et al., 2020; Zhu et al., 2020) (Figure 1).