In addition, the amino acids in neutralizing epitopes of S INDEL strains were the same as that of the majority of NA highly virulent strains (Table 3 ), suggesting their cross-neutralization ability and confirmed by our previously reported in vitro and in vivo studies (Lin et al., 2015a,b) . Recently, serological cross-reactivity and crossneutralization between S INDEL (USA/IL20697/2014) and non-S INDEL (USA/IN19338/2013) strains were studied by Chen et al.