Scientists appear to have solved an enduring mystery surrounding the 1918 outbreak of Spanish flu which killed millions worldwide.
Estimates say the epidemic took 50 million lives, more than the First World War. Unlike most bird flu strains, it was lethal amongst young, healthy people.
Canadian lab reconstructed the Spanish flu virus from human tissues preserved in the Alaskan permafrost and infected macaque monkeys. Their findings were reported on Thursday in the journal Nature, and should give a better view of how the virus killed humans than earlier work with infected mice.
It turns out that the H1N1 Spanish flu virus (the current bird flu threat is from H5N1, the nomenclature derived from the proteins which coat the virus) killed 50 million by over-stimulating their immune system, causing the lungs to inflame and rapidly fill with liquid. Lead author Professor Yoshihiro Kawaoka of the University of Wisconsin said: "Essentially people are drowned by themselves."
So a young, healthy person with a young, healthy immune system would be a ripe victim for the 1918 strain. Associated Press reports co-author Michael Katze, of the University of Washington, said: "It was the robustness of the immune system that helped victimize them."
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