Timeline: The secret history of swine flu

Six months ago, swine flu emerged as a massive threat to global health. It seemed to come out of nowhere, but our timeline explains how the origins of the H1N1 pandemic go back more than a century

1889

Prior to 1889, the main flu virus circulating in humans has been from the H1 family. But this year, a new strain of H2 flu emerges in Russia and spreads around the world, killing about 1 million people. Afterwards, H2 replaces H1 in humans. Such replacements seem to be a regular feature of flu pandemics. Read the rest of this entry »