In 1918 and 1919, the world took on a new, invisible enemy: the so-called "Spanish flu" pandemic sweeping the globe. The pandemic left tens of millions of casualties in its wake as it devastated one community after another. Given the scale of the disease, what was it like to live through the influenza pandemic? A particularly aggressive strain of influenza began infecting WWI troops in 1918. Though there isn't a consensus on where it came from, it's likely the strain originated in Kansas and spread to the rest of the world via troop movements.