Genomic signatures of human versus avian influenza A viruses.

Position-specific entropy profiles created from scanning 306 human and 95 avian influenza A viral genomes showed that 228 of 4591 amino acid residues yielded significant differences between these 2 viruses. We subsequently used 15,785 protein sequences from the National Center for Biotechnology Information (NCBI) to assess the robustness of these signatures and obtained 52 "species-associated" positions. Specific mutations on those points may enable an avian influenza virus to become a human virus.