Encephalitis Lethargica: The Sleepy Sickness Plague

Your patient has not moved in a decade. She sits where the orderlies place her, eyes open, one hand raised mid-gesture as if the film of her life jammed on a single frame. Then someone tries a new drug on her, and one morning she says good morning back.

A plague that arrived with the war

Encephalitis lethargica, the "sleepy sickness," not to be confused with the tsetse-borne sleeping sickness of the tropics, swept the world between roughly 1915 and 1927, shadowing the First World War and the 1918 influenza pandemic. The Viennese neurologist Constantin von Economo described it in 1917 after seeing patients who burned with fever, then sank into a sleep so deep it shaded into coma, sometimes never fully lifting. Estimates are imprecise, but the outbreak is thought to have killed as many as a million people and affected several million more before it faded almost as mysteriously as it came.

Its cruelty was in the variations. Some patients could not stay awake; others swung to the opposite pole and could not sleep at all. Many suffered oculogyric crises, in which the eyes rolled upward and locked for hours. Worst of all was the aftermath: survivors who seemed to recover often developed, months or years later, a post-encephalitic parkinsonism that gradually froze them into living statues, awake, aware, and unable to move or speak.

The awakenings

Those frozen survivors are why the disease is remembered outside medicine. In 1969 the neurologist Oliver Sacks began treating a ward of them at Beth Abraham Hospital in the Bronx with L-DOPA, the then-new Parkinson's drug. Patients who had been immobile for decades abruptly returned, talking, walking, remembering the world they had left in the 1920s. The revivals were unstable and often could not be sustained, and Sacks recorded them in his 1973 book "Awakenings," later filmed with Robert De Niro and Robin Williams. It remains one of medicine's strangest documented episodes: consciousness switched back on after thirty silent years, then flickering out again.

The cause nobody pinned down

Here is the part that keeps the case open: no one has ever proven what caused it. The timing invited a link to the 1918 flu, but careful work has never confirmed the influenza virus as the culprit, and the two waves did not map cleanly onto each other. Later researchers, notably Russell Dale and colleagues in 2004, argued for an autoimmune reaction possibly triggered by a streptococcal infection, the body's defences turning on the brain's basal ganglia. It is a strong hypothesis, not a verdict.

And then the disease essentially left. After the late 1920s the epidemic form vanished, leaving only rare, scattered cases that still appear and still puzzle clinicians. A worldwide plague that froze people alive, arrived without clear cause and departed without one, is exactly the kind of event that resists a clean ending.

Below, readers have filed accounts of unexplained illness, of relatives who "went away" and came back, and voted them True, Fake or Not sure. Read the medicine, then read the residue, and add your judgement.