It's hard to believe but 1918 flu pandemic killed an estimated 50 million people.
By comparison, World War I claimed an estimated 16 million lives.
Lasting form January 1918 to December 1920, it infected 500 million people, about a quarter of the world's population at the time.
Thankfully, after the lethal second wave struck in late 1918, new cases dropped abruptly almost to nothing after the peak in the second wave.