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The 2009 influenza H1N1 pandemic - laboratory release or naturally evolving strain?

Emergency Response 250 x 250During the initial stages of the influenza A(H1N1) pandemic, the WHO was contacted by a virologist who, from his analyses of the available genetic sequences of strains, put forward a hypothesis that circulating viruses were from a laboratory derived virus. If true, this would have had potentially serious implications.

In a very short time, and in close connection to the WHO Director General and senior colleagues in the Food and Agriculture Organisation and the World Organisation for Animal Health, we worked to analyse available strains from swine and humans to determine the veracity of this hypothesis. Our analysis showed that natural evolution of the pandemic strain of influenza was the most likely source of the virus.