The scientists then asked of these trees what are the geographic connections between the isolated viral strains?
These resulting diagrams were then used as the basis for an interactive map that traces the genetic, geographic and evolutionary history of avian influenza over 12 years. The highly pathogenic lineage of avian flu that crossed Asia and Africa can be traced to an isolate taken from a goose in 1996. Little genetic data is available for H5N1 viruses isolated before that.
To avoid creating a complex map that looks like "spaghetti thrown on the screen," Janies and colleagues also simplified the map's design. Green lines represent transmission pathways most strongly supported by the research findings. Yellow lines indicate less certainty. Lines also are colored differently depending on whether they indicate an incoming or outgoing virus from a specific location. And users can search for specific transmission routes rather than seeing all transmission events on the map at once.
The maps represent scientists' best approximation of avian flu transmission based on the information available, Janies explained. Without access to every complete genome of every flu virus that ever infected a bird or human, researchers can never fully track evolutionary relationships, genetic histories and specific locations of each outgoing and incoming viral transmission.
"Collect and share as much data as possible and let the data tell the story," he said. "We're honest about the uncertainty our results may have but even with partial data, we can infer much about a virus in an area based on its sources."
The method has already been applied to studies of the H1N1 flu currently infecting millions of people in the United States. International cooperation spearheaded by the NIH, GISAID and the Centers for Disease Control and Prevention has resulted in ready avai
|Contact: Daniel Janies|
Ohio State University