In the 20th century, people were massively falling into lethargic sleep
Encephalitis lethargica — one of the strangest epidemics in history. Between 1917 and 1930, the disease struck more than a million people worldwide, killed about half of those afflicted, and left survivors trapped inside their own bodies, sometimes for decades. People remained conscious but could neither move nor speak. And there was a great risk that they would be buried alive.
What Is Encephalitis Lethargica in Simple Terms
The name sounds complex, but it’s easy to break down. Encephalitis is inflammation of the brain. Lethargica comes from the word lethargy, meaning deep sleepiness and sluggishness. Together it means: inflammation of the brain that causes a person to fall into a morbid slumber.
That’s exactly how the disease manifested. According to Mental Floss, it all started quite ordinarily: fever, headache, sore throat, weakness — symptoms resembling a common cold or flu. But then the disease struck the nervous system, and things began that doctors had never seen before. Some patients fell asleep for days and weeks; they could be awakened, but immediately slipped back into sleep. Others, on the contrary, couldn’t sleep at all and suffered from extreme agitation.
But the worst was yet to come. In those who survived the acute phase, months or even years later, a condition developed resembling Parkinson’s disease. Muscles stiffened, faces lost expression, movements slowed to a near standstill. Some people froze completely — they couldn’t move, couldn’t speak, yet remained fully conscious. This gave the disease its unofficial name — the sleeping sickness of the 20th century.
How the Sleeping Sickness of the 20th Century Spread Across the World
The first cases of the strange sleeping sickness were recorded in Europe during the winter of 1916–1917, in the midst of World War I. Doctors gave all sorts of diagnoses — meningitis, multiple sclerosis, delirium — but none quite fit.
In the spring of 1917, Austrian neurologist Constantin von Economo addressed the Vienna Psychiatric Society and described a new disease, which he called encephalitis lethargica. Almost simultaneously in France, military physician René Cruchet encountered the same kind of patients among soldiers.
From that point, the epidemic rolled across the world, through Europe, North America, and other regions. According to estimates by the American Society for Microbiology, between 1917 and 1930, more than a million people fell ill, and about 500,000 died. Survivors were often left with severe neurological impairments for the rest of their lives.
And by the 1930s, the epidemic simply… faded away. Just as suddenly as it had begun. Since then, only isolated cases have been recorded.
Symptoms of Encephalitis Lethargica
The disease was insidious in that it manifested completely differently in different people. Doctors identified several main forms.
- Somnolent form: the patient slept almost continuously; they could be awakened but would immediately fall asleep again, even during meals or conversation;
- Insomnia and agitation form: the person couldn’t sleep and became anxious or aggressive;
- Motor disturbances: tremor, tics, involuntary movements, difficulty with speech and eye control;
- Psychiatric changes: hallucinations, emotional outbursts, dramatic personality shifts. In children, behavioral changes were especially common.
Roughly a third of those affected died during the acute phase. Another third recovered without lasting effects. But the remaining third — hundreds of thousands of people — sustained severe neurological damage for life. It was they who, years later, turned into “living statues”: motionless, silent, yet aware of everything around them.
Survivors of encephalitis lethargica lost the ability to move but remained conscious
The last known patient from the era of the great epidemic, Philip Leather, died in 2002. He was diagnosed in 1931, when he was 11 years old. He spent his entire life in a psychiatric hospital.
Encephalitis Lethargica and the Spanish Flu
This question has tormented scientists for over a hundred years. Encephalitis lethargica and the Spanish flu pandemic of 1918 raged at practically the same time and in the same regions, so the coincidence looks too obvious to ignore.
However, modern research leans toward there being no direct connection between them. Analyses of preserved brain samples from patients, conducted since the 1970s, have not confirmed the presence of the influenza virus. As the authors of a major review in the Journal of NeuroVirology note, there is little direct evidence linking influenza and encephalitis lethargica, although it cannot be entirely ruled out yet due to technical limitations of the analyses.
There is another fact: the first cases of the sleeping sickness were recorded in 1916–1917 — before the Spanish flu pandemic reached full force. This doesn’t definitively disprove the connection, but it does cast doubt on it.
Among current hypotheses, researchers are considering theories about an unknown virus (possibly an enterovirus) and about an autoimmune reaction in which the immune system mistakenly attacks the brain itself after some infection.
Awakenings After Encephalitis Lethargica
Perhaps the most famous episode in the history of the sleeping sickness is associated with British neurologist Oliver Sacks. In 1966, while working at Beth Abraham Hospital in the Bronx, he discovered about 80 patients who had been in a catatonic state for more than 40 years.
In 1969, Sacks decided to prescribe them the experimental drug levodopa (L-DOPA), which was only just beginning to be used for Parkinson’s disease. The result was astonishing: people who hadn’t moved or spoken for decades suddenly woke up and began walking, talking, and recognizing loved ones. Sacks compared it to the awakening of dormant volcanoes.
Oliver Sacks described how patients after decades of immobility suddenly returned to life
However, the joy was short-lived. Over time, the drug’s effect weakened, patients developed severe side effects, and many sank back into their former state — or even worse. This story became the basis for Sacks’s book Awakenings (1973), and later the film of the same name starring Robert De Niro and Robin Williams.
Sacks’s story accomplished something important: it showed the entire world that inside those motionless bodies, people were still alive. Brain diseases like encephalitis lethargica serve as a reminder of how fragile the connection between consciousness and the body’s ability to obey it can be.
Why Encephalitis Lethargica Almost Disappeared
This is perhaps the greatest mystery of all. A disease that struck more than a million people across several continents virtually vanished by the 1930s. Since then, only extremely rare isolated cases have been recorded, and even those are difficult to definitively attribute to the same disease.
Scientists know neither the exact pathogen, nor the mechanism of transmission, nor the reasons for the epidemic’s disappearance. All analyses — serological tests, PCR, immunohistochemistry, and even modern next-generation sequencing — have failed to identify a specific viral agent.
The possibility of the epidemic recurring remains an open question. If the disease was indeed linked to some unknown pathogen or an autoimmune reaction following a respiratory infection, then the emergence of new pandemics, such as COVID-19, compels researchers to keep this topic in their sights.
More than a hundred years ago, doctors preserved brain samples from deceased patients in the hope that future technologies would unlock the mystery. Modern science has studied them — but the answers remain elusive.
