Worobey compared samples from different H1N1 outbreaks to try to find the origins of the 1918 catastrophe. He thought this might settle debate between the two competing theories – a jump from birds or the reshuffling of genes between existing human and swine varieties. Instead in the Proceedings of the National Academy of Sciences he proposes a third option in which a human flu virus with the H1 protein in circulation for 10-15 years gained the N1 genes from a version infecting birds. He believes previous researchers have missed this because after 1922 a slightly different form of H1 displaced the one responsible for the 1918 outbreak, and scientists have been examining the wrong one until samples taken during the original outbreak were found.
"It sounds like a modest little detail, but it may be the missing piece of the puzzle," Worobey said. "Once you have that clue, many other lines of evidence that have been around since 1918 fall into place."
