Don't Blame Birds for 1918 Flu

[Staff]

Don't Blame Birds for 1918 Flu
By Martin Enserink
ScienceNOW Daily News
13 July 2009

Don't Blame Birds for 1918 Flu -- Enserink 2009 (713): 1 -- ScienceNOW
excerpts from above:

It has become almost common wisdom that the virus that caused the 1918 flu pandemic was an avian strain introduced into the human population shortly before the pandemic erupted. But a new study disputes that hypothesis, arguing instead that genes of the 1918 virus had circulated in mammalian hosts, most likely pigs and humans, for several years before 1918. Multiple gene-swapping events brought them together in a single killer strain, say the researchers; improving surveillance in humans and in swine could alert scientists to such events early in the future.

To study the origins of the three 20th century pandemic flu viruses, Robert Webster of St. Jude Children's Research Hospital in Memphis, Tennessee, and his colleagues took DNA sequences of thousands of flu isolates dating back as far as the 1930s--as well as the 1918 strain--and fed them into models that calculate the most likely evolutionary relationships between them. They report today in the Proceedings of the National Academy of Sciences that genes of the 1918 virus were most likely present in swine or human hosts at least 2 and possibly 15 years before the pandemic began and combined to form the deadly virus during multiple reassortments, presumably rare events in which flu viruses exchange genes. "The data don't really fit with the idea that it was a recent avian introduction," says Gavin Smith of the University of Hong Kong, who carried out the computational analysis.