One of the deadliest pandemics, the "Spanish Flu", killed off what percentage of the human world population at the time?

The story behind the answer

Correct answer: 3 to 6 percent. The 1918–1919 “Spanish Flu” (an H1N1 influenza) killed an estimated 50 million people worldwide—some estimates go higher—when the global population was about 1.8–1.9 billion. That puts the death toll at roughly 3–6% of humanity, matching this option.

Context to remember: despite the name, the pandemic didn’t start in Spain; wartime censorship in many countries muted reports, while Spain’s free press openly covered the outbreak, making it seem worse there. The virus spread rapidly via World War I troop movements and ship travel and was unusual for its high mortality among young adults, partly due to overactive immune responses. Memory hook: think “one in twenty people”—about 5%—a stark measure of its global impact.