The Spanish Flu Epidemic
But there’s one other way very striking feature of that our history, and that’s the enormous dip in 1918. That was the pandemic influenza of that interval - it was called the Spanish Flu, which is almost a guarantee that is started somewhere else. Probably Kansas was the original site of origin, an army contingent being the first recognized point of outbreak, as those troops went overseas were certainly part of the movement, not all of it, of transmitting that flu to Europe. [It] came back in even more aggravated form in the following spring.
And the result was the most catastrophic event in human demography in the United States in the 20th century. It was half a million deaths; 25 million deaths around the world, which is a good match for the number of combat casualties that we had in World War I with all the slaughter that there was in the trenches and so on. It’s a forgotten episode. Most folks if reminded will say “my grand uncle died of it” or something of that kind, but it is astonishing how little attention has been paid to it until recently.