Interactive map to track avian flu spread
US scientists have created an interactive 'supermap' to follow the mutations and spread of bird flu around the globe over time.
According to a new study involving University of Colorado at Boulder (CU-Boulder) and Ohio State University researchers, it should help researchers and policy makers better understand the virus and anticipate further outbreaks.
The research team used data from the known evolution and spread of the avian flu, known as H5N1, to create a roadmap of viral spread in time and space, said CU-Boulder ecology and evolutionary biology Assistant Professor Robert Guralnick, a study co-author.
They projected genetic and geographic information onto an interactive globe using Google Earth technology, allowing users to analyse movements and changes in the genetic blueprints of known avian flu sub-strains that have been sequenced since the virus was first detected in Guangdong, China, in 1996.
The researchers used the novel technology to chart the spread of H5N1 through Asia, Indonesia, the Middle East and Europe by various hosts, including its transport by specific orders of birds and mammals.
They also used the supermap to track key genetic traits prevalent in some avian flu genomes, which appeared to confer the ability of H5N1 to more readily infect mammals, including humans, explained CU-Boulder graduate student Andrew Hill, a study co-author.
"This is a completely new method of integrating and sharing knowledge about disease spread, giving people a quick and easy way to make sense of the changes," said Hill, chief architect of the visualisation portion of the collaborative research project.
Like the legend of a roadmap, colours and symbols on the supermap indicate which types of hosts carry the virus or the distribution of genotypes of interest, Hill explained.
"This allows us to test hypotheses on the geographic distribution of strains that contain what laboratory studies have suggested are the key genotypes that allow avian strains of the influenza virus to infect mammals," he said.
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 US 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.
Bird-to-human mutations
Scientists think that 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 added.
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 Daniel Janies of Ohio State University.
The team also used the supermap to visualise 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.
The avian flu epidemic was first detected in wild aquatic birds in Guangdong in 1996 and spread to chickens and a few humans in Hong Kong by 1997.
From 1997 to 2005, the virus emerged in several Southeast Asian countries and spread through multiple hosts in Japan, Korea, Russia the Middle East and India.
In the past two years the virus has spread to Western Europe and re-emerged in Korea.
While H5N1 is not highly communicable to humans or between humans, experts are concerned that future mutations have the potential to make the bird flu significantly more contagious.
According to the World Health Organization, there have been 269 cases of the disease in humans since the initial outbreak in 1996, including 164 deaths.
A paper on the research is being published in the April issue of the Systematic Biology journal.
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