3.1  Genomics of 2019-nCoV
According to the genome analysis, 2019-nCoV belongs to Sarbecovirus subgenus, Betacoronavirus genus of the subfamily Orthocoronavirinae in the family Coronaviridae of the suborder cornidovirineae of the order Nidovirales [20,26]. Similarly to other coronaviruses, 2019-nCoV is an enveloped, single-stranded positive-sense RNA (+ssRNA) with around 29,900 nt, showing a typical coronavirus appearance under electron microscopy [20]. The genome organization is 5′-leader-UTR-replicase-S (Spike)-E (Envelope)-M (Membrane)-N (Nucleocapsid)-3′UTRpoly (A) tail with accessory genes interspersed within the structural genes and the 3′ end of the genome [26].
2019-nCoV shares 79.5% nt identity with SARS-CoV and 96% identity with bat-CoV-RaTG13 [20]. The genetic characteristics of 2019-nCoV are significantly different from SARSr-CoV and SARS-CoV, which are closely related only to the specific bat SARS-like coronaviruses, bat-CoV-RaTG13 and bat-SL-CoVZC45, with 96% and 86.9% nucleotide sequence identities, respectively [20]. Therefore 2019-nCoV is considered as a SARS related coronavirus (SARSr-CoV) by pairwise protein sequence analysis (Fig. 1 ) [20].
Fig. 1 The evolutionary position of 2019-nCoV. The phylogenetic tree was constructed based on the complete genomic sequences of 2019-nCoV and related CoVs by using the neighbor-joining (NJ) method with 1000 bootstrap. The novel 2019-nCoV detected strains were indicated in bold with solid squares. Abbreviations are as follows: SARSr coronavirus, SARS-related coronavirus. The accession numbers of CoVs were showed in the figure. Bootstrap values above 50 were shown.