The Spanish Flu Pandemic
The 1918 influenza pandemic infected a third of the world's population and killed an estimated 50 million people — more than World War I itself.
In the spring of 1918, a novel H1N1 influenza virus emerged and spread with devastating speed through a world exhausted by World War I. Unlike typical flu strains that killed the very young and very old, the Spanish Flu disproportionately struck healthy adults aged 20–40, likely through a cytokine storm — an overreaction of the immune system. The pandemic came in three waves: a mild spring wave, a catastrophic fall wave, and a final winter wave. An estimated 500 million people — one-third of the world's population — were infected, and 50–100 million died. Wartime censorship suppressed news in combatant nations; neutral Spain reported freely, giving the pandemic its misleading name. The Spanish Flu remains the deadliest pandemic in modern history and a benchmark against which all subsequent outbreaks are measured.
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