In 1918, the world had maybe 2 billion people, mostly rural.
In 1918, the dominant way people travelled was by train or ship, or more locally still by horse. A few urban areas had streetcars or subways. Cars and airplanes existed, but cars were not dominant, and commercial air travel didn't exist.
Despite this, the flu virus still managed to travel around the world and kill something like 20-30 million people. (As many as WW1 did itself, perhaps more.)
Today we have 7.5 billion, mostly in tightly-packed urban areas.
Today, people travel faster and farther, mostly by car, or train, but the real spreader of disease is jet airlines. before a journey from Asia or Europe to North America took place in 12 days; today, from continent to continent 12 hours.
Agencies like WHO and CDC have known & feared this sort of pandemic for decades. Militaries have response plans for biological weapons which game out scenarios just like this; that because they have designed biological weapons that would work just like COVID19 does.
The thing we have going for us now, that 1918 did not, is that medically speaking they are much better at keeping people alive. We are better at identifying the infected, better at analyzing the virus, and better at dealing with symptoms. In 1918, it was basically "cool the patient's forehead, feed them broth, and pray."
So we shall see how this plays out. The way it spreads exponentially, versus our ability to take the hit and survive.
