You do know why they called it “The Spanish Flu”, right?
Because, Spain being neutral, didn’t have censorship in place, unlike all the countries fighting. So the first stories came from the Spanish press, and that’s why it was called “The Spanish Flu”.
Speculation is, that was maybe the main factor in the Germans losing the war, as they were wiped out by the flu.
From what I’ve read, the first confirmed infections were at Fort Riley, KS. I had a great-uncle who died from that.