Evolutionary dynamics of influenza A nucleoprotein (NP) lineages revealed by large-scale sequence analyses

► We conducted large-scale phylogenetic analyses of influenza A NP genes. ► Eight lineages identified: three host specific, two cross-host and three geographic-specific. ► Substitution rates, TMRCAs, and selection pressures vary in different lineages. ► Evolution of influenza A viruses strongly associated with host adaptation.