The team studied genomic sequence data from 351 different strains of the avian flu collected in the field, said Guralnick, who is also Curator of Invertebrate Zoology at the University of Colorado Museum. A click by users on viral "isolates" generates computer windows revealing diagnostic mutations that make each strain unique, and the information is linked by computer to the National Institutes of Health's GenBank, a database containing more than 75 million sequence records.
As part of the effort, the team looked at two key proteins found on the surface of H5N1 strains known as hemaglutinin, or HA, and neuraminidase, or NA. Scientists think if a virulent strain of H5N1 adapts to succeed at human-to-human transmission, it would likely involve mutations by the two proteins, said Guralnick. No mutations associated with NA and HA were linked to any specific bird or mammal host, he said.
But the team did find a strong association between a specific genotype, Lysine-627, in a segment of the viral genome called the polymerase basic protein, or PB2, and in mammalian hosts in the field. "While this genotype is not exclusive to mammals, we think it is important to track how this PB2 mutation is spreading because it appears to be so infective and deadly in mice," said Janies.
The team also used the supermap to visualize the spread of H5N1 in various parts of the world by specific orders of birds and mammals, including waterfowl, domestic fowl, shorebirds, raptors, songbirds, hoofed mammals and carnivores, said Guralnick.