The 1918 flu epidemic virus — still with us

July 25, 2009  |  General

The world-wide influenza epidemic (which is then called a pandemic) of 1918-1920 infected an estimated one-fifth of the world’s population and killed 50 million people, far more than even died in World War I. It was a new strain of flu which, unlike previous epidemics, struck young adults in their prime. What I didn’t know about the 1918 strain of flu is that, essentially, it is still with us. It is the ancestor of many subsequent, milder epidemics. It is also the direct ancestor of the current flu strain we are all calling “swine flu.”

The 1918 strain did disappear for a time between 1957 and 1977. Its reappearance in the population probably was the result of an accidental release from a research laboratory that was studying the 1918 virus. Once it escaped and was back in the wild, so to speak, it never left us.

The natural reservoirs for influenza are humans, birds, and swine. How the various versions of the virus recombine and jump from species to species and back again is a fascinating story. If you are interested in how that works, you can read some excellent discussions here and here.


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