Sequence alignment of the S2 fragment corresponding to residues 1029 to 1192 shows that this fragment, which encompasses the heptad repeat (HR)2 but not HR1, is highly conserved in SARS-CoV-1 and SARS-CoV-2 (Figure 1). When compared with additional reference sequences from bat RaTG13 (closest bat precursor), MERS and human common cold coronaviruses 229E, NL63, OC43 and HKU1 (Figure 1), it becomes apparent that the amino-acid identity between SARS-CoV-2 and SARS-CoV-1 is much higher in this region (93%, Table) than over the full protein length (78%, Table) and the similarity drops sharply (< 40% in this region) when considering MERS and the other coronaviruses infecting humans regularly.