Figure 1. Phylogeny of hemagglutinin (A) and neuraminidase (B) genes from 8 HPAI (H5N1) viruses collected in Nigeria during the second half of 2007 (▲), in comparison with previously identified sublineage A (EMA 2), sublineage B and C (EMA 1), and (EMA 3) strains (1,3). The tree was calculated by using the maximum likelihood method implemented in PAUP 4.0 (7). The substitution model was obtained by using MODELTEST (8). Bootstrap values (%) were calculated with the maximum-likelihood method with 1,000 replications and are indicated on key nodes. Scale bars represent ≈1% of nucleotide changes between close relatives. A/duck/Anyang/AVL-1/2001 was used as an outgroup.