The Sleep That Lasted Decades: The Forgotten Plague of 1917

2025-12-10 · Strange Mass Events · 2 min read

In the winter of 1916 and 1917, as the First World War ground on, patients began arriving in European clinics with a bewildering complaint. They were unbearably sleepy. Some drifted into a stupor from which they could barely be roused, sleeping for days or weeks; a few slipped into coma and did not wake. The Viennese neurologist Constantin von Economo studied them, recognized a distinct new disease, and gave it a name: encephalitis lethargica, an inflammation of the brain that brought sleep.

Over roughly the next decade the illness spread across the world, following no clear path. It reached Britain, France, North America and beyond, appearing in cities and villages alike. Estimates of its toll vary widely, but a commonly cited figure holds that around a million people were affected and perhaps half a million died during the years of the epidemic. It struck as the great influenza pandemic raged, and the two have been tangled together ever since.

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