Fig. 1: Comparative analysis of human coronavirus emergence and Sarbecovirus HR1 sequence alignment.

a Emerging timeline for human coronaviruses, among which Disease X represents a threat of a potential future coronavirus-mediated pandemic. b Sequence alignment of HR1 domains of sarbecoviruses from four clades (SARS-CoV-2 numbering). NTD, RBD, CTD1 and 2, FP, HR1, HR2, TM and CT represent N-terminal domain, receptor binding domain, C-terminal domain 1 and 2, fusion peptide, heptad repeat 1 (HR1), heptad repeat 2 (HR2), transmembrane domain and cytoplasmic terminus, respectively.