90-year Evolution Of Swine Flu

ScienceDaily (July 5, 2009) — The current H1N1 swine flu strain has genetic roots in an illness that sickened pigs at the 1918 Cedar Rapids Swine Show in Iowa, report infectious disease experts at the University of Pittsburgh Graduate School of Public Health in the New England Journal of Medicine. Their paper, published online June 29 and slated for the July 16 print issue, describes H1N1's nearly century-long and often convoluted journey, which may include the accidental resurrection of an extinct strain.

"At the same time the 1918 flu pandemic was rapidly spreading among humans, pigs were hit with a respiratory illness that closely resembled symptoms seen in people," said senior author Donald S. Burke, M.D., dean, University of Pittsburgh Graduate School of Public Health. "Early experiments confirmed that this 1918 swine virus and a human strain emerged about the same time. Since then, this ancestor virus has re-assorted genetically with other influenza strains at least four times, leading to the emergence of the new 2009 strain, which has retained some similarities to the original virus."

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