FIG. 2.

Genetic reassortment and emergence of influenza A virus (H5N1) in Asia from 1999 to 2005. The eight gene segments (represented by horizontal bars) starting from top downwards are PB2, PB1, PA, HA, NP, NA, M, and NS. Each color represents a distinct virus lineage. Red represents the A/Goose/Guangong/1/96-like lineage. Distinct genotypes (i.e., gene constellations) are denoted by a letter. The origin of the 1997 virus in Hong Kong is not represented here but was a separate reassortment event with only the HA being derived from A/Goose/Guangdong/1/96 and the other seven gene segments being derived from H9N2 and H6N1 avian influenza viruses found in quail. (Adapted from reference 127 by permission from Macmillan Publishers Ltd.)