New study challenges conventional wisdom on history of flu

A study reconstructing the evolutionary tree of flu viruses challenges conventional wisdom about how influenza moves between animals and may increase understanding of historical outbreaks, according to a study recently published in Nature.

Researchers at the University of Arizona and the University of Edinburgh conducted a comprehensive analysis of the evolutionary relationships of influenza virus across different host species over time. The study challenges several tenets of conventional wisdom about flu, for instance, the idea that the flu virus moves unidirectionally from wild birds to domestic birds. The study also resolves the origin of the virus that caused an unprecedented and severe flu outbreak in 1918.

"We now have a really clear family tree of theses viruses in all those hosts -- including birds, humans, horses, pigs -- and once you have that, it changes the picture of how this virus evolved," Michael Worobey, the co-leader of the study, said. "The approach we developed works much better at resolving the true evolution and history than anything that has previously been used."

Worobey said that by accounting for the fact that the virus evolves at different rates in different species, the evolutionary trees for the viruses make more sense than ever before. Worobey and his partner Andrew Rambaut developed software to analyze more than 80,000 gene sequences representing the global diversity of the influenza A virus.

The study may change how scientists and health experts look at flu's history, how it changed genetically over time and how it jumped between different host species. The findings could help scientists generate better assessment of health risks for populations and develop more effective vaccines.