Figure A2. Histograms on comparing 306 human versus 95 avian influenza A viruses, based on nucleotide pairwise sequence identities. Vertical axis shows the count for pairs of sequences with specific percent identity (rounded to integer). Red bars represent frequencies for 'homo' pairs – sequences of the same host species (human to human, or avian to avian); blue bars represent frequencies for 'hetero' pairs – pairs that cross host species (human to avian, or avian to human). Adobe Acrobat PDF available at http://wwwnc.cdc.gov/eid/pdfs/06-0276-FA2.pdf (6 pages).