The most lethal pandemic in recorded history, killing an estimated 50–100 million people worldwide — more than the First World War — in roughly two years between 1918 and 1920, disproportionately striking young adults rather than the elderly, spreading along the military transportation networks of the First World War, and being suppressed from public awareness by wartime censorship in most belligerent countries, producing a collective amnesia about its scale that lasted for most of the 20th century.
The deadliest event in human history since the Black Death killed more people than the war it accompanied — and then was largely forgotten. Fifty million dead, possibly a hundred million, in roughly two years: more than the trenches, more than the bombing, more than all the military campaigns of the First World War combined. It killed healthy young adults in their prime rather than the elderly, producing a mortality curve unlike any influenza before or since. Wartime censorship suppressed reporting in most countries; only neutral Spain reported freely, giving the pandemic a name — the Spanish flu — that had nothing to do with its origins. Within a decade of its end, it had largely vanished from public memory. The Great War had its monuments and its literature. The pandemic had neither.