Thursday, August 13, 2009

In pursuit of a pathogen’s parents

12 August 2009

Inadequate animal monitoring policies may have given ancestors of ‘swine flu’ the opportunity to evolve into a pandemic threat

Since the first reported cases in humans earlier in 2009, so-called ‘swine flu’ — more accurately, the swine-origin influenza A virus (S-OIV) — has garnered considerable media attention and public concern, having emerged seemingly from nowhere as the first potential pandemic of the 21 Century.

Recent findings from an international team led by Yi Guan of the University of Hong Kong, China, and Andrew Rambaut of the University of Edinburgh, UK, have now helped to chart how this new threat arose1. The researchers analyzed evolutionary change in viral genes from samples taken in different years and geographic locations.

Their findings support a model in which pigs act as ‘mixing vessels’ for recombination between different strains of virus from swine, humans and birds, and in which this shuffling process was facilitated by the trafficking of infected animals between Europe, Asia and North America.

Interestingly, the evidence suggests that ancestors of the currently active strain of S-OIV have been circulating and exchanging genetic material in pigs for more than a decade. Guan and Rambaut also note considerable gaps in the viral record leading up to S-OIV’s emergence in humans, and conclude that “lack of systematic swine surveillance allowed for the undetected persistence and evolution of this potentially pandemic strain for many years.”

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