Coronaviruses (CoVs), a large family of single-stranded RNA viruses, can infect animals and also humans, causing respiratory, gastrointestinal, hepatic, and neurologic diseases (Weiss and Leibowitz, 2013). As the largest known RNA viruses, CoVs are further divided into four genera: alpha-coronavirus, beta- coronavirus, gamma-coronavirus and delta-coronavirus (Yang and Leibowitz, 2015). To date, there have been six human coronaviruses (HCoVs) identified, including the alpha-CoVs HCoVs-NL63 and HCoVs-229E and the beta-CoVs HCoVs-OC43, HCoVs-HKU1, severe acute respiratory syndrome-CoV (SARS-CoV) (Drosten et al., 2020), and Middle East respiratory syndrome-CoV (MERS-CoV) (Zaki et al., 2012).
