Figure 1. Phylogenetic tree of the hemagglutinin subtype 7 nucleotide sequence, which includes both low pathogenic and highly pathogenic avian influenza viruses from Chile. Representative avian and equine H7 influenza gene sequences are also included. The tree was generated with PAUP 4.0b4 computer program with bootstrap replication (500 bootstraps) and a heuristic search method. The tree is rooted to A/Equine/London/1416/73, and branch lengths are included on the tree. Standard two-letter postal codes are used for states in the United States. TK, turkey; CK, chicken; DK, duck; and FPV, fowl plague virus.