Stuff You Should Know — "The Mystery of the Sleepy Sickness"

Hosts: Josh Clark & Chuck Bryant
Original Air Date: October 2, 2025

Episode Overview

In this classic “medical mystery” episode, Josh and Chuck dive deep into the bizarre and unsettling story of Encephalitis lethargica—also known as the “sleepy sickness”—a disease that tore through the globe from 1916 to the 1930s, left hundreds of thousands dead or potentially frozen in their own bodies, then abruptly disappeared. The hosts explore the epidemic’s origins, symptoms, attempts to identify its cause, and the mysterious chronic cases still referenced in medicine and popular culture today.

Key Discussion Points & Insights

1. What Was the “Sleepy Sickness”? (01:17–04:07)

• Encephalitis lethargica, or EL, struck suddenly in the 1910s–20s, crippling patients with sleep-like states, paralysis, coma, and even death.
• Chuck: “We’re talking about an outbreak that happened in the early 20th century…people would kind of out of nowhere lose mobility. Some would fall into a coma-like state…Many people died within days. It’s a medical mystery because we still don’t know exactly why it happened or why it just kind of suddenly went away.” (02:37)

2. Initial Observations and Dr. von Economo (04:18–06:10)

• Dr. Constantin von Economo in Vienna identified and described the syndrome after puzzling over flu-like symptoms and neurological changes in patients who didn’t match any then-known diagnoses.
  • Also referenced: French physician Dr. René Cruchet, who considered a behavioral link.
• Von Economo stressed it was likely transmissible and infectious, not just behavioral.

3. Symptoms and Ubiquity (06:10–09:28)

• Starts with fever and malaise, progressing to severe drowsiness (hypersomnolence), and unpredictable neurological or psychiatric symptoms.
• Josh: “They weren’t like Sleeping Beauty…They might have their hand in the air and their mouth open in a silent scream. Their eyes were open, they just weren’t moving at all.” (03:14)
• Personality changes could manifest—kleptomania, psychosis, or mood alterations.

4. Age Range and Mortality (08:31–09:28)

• Affected all ages, but half of cases were in people aged 10–30.
• Mortality rate dramatic; some died within days or weeks.
• Set the stage for “chronic” post-encephalitic conditions.

5. Subtypes of Encephalitis Lethargica (09:28–14:24)

• Von Economo categorized three main acute subgroups:

  • Somnolent–ophthalmoplegic (most common):

    • Pronounced sleepiness, ocular paralysis, potential waxy flexibility (patients poseable like wax figures).
    • Delirium, catatonia, confusion.
    • Josh: “You can pose somebody in this state any way that you want them to. So you have to be very kind when you’re dealing with patients like this.” (13:38)

  • Hyperkinetic variety:

    • Marked by mania, involuntary vocalizations, jerky movements, and sometimes a reversed sleep cycle.
    • Hallucinations and nerve pain possible.

  • Ameostatic-akinetic (least common):

    • Immobility bordering on total body “statue state;” classic “frozen” symptom.

• Memorable Moment: Chuck jokes “waxy flexibility” could be a Guided by Voices album (14:01).

6. Mental Awareness & Chronic Cases (14:24–16:21; 19:21–23:39)

• Profound horror: Many chronic sufferers were mentally present yet trapped, unable to communicate or move for years or decades.
• Josh: “They’re essentially in the same boat where they’re aware, time’s passing, people are interacting with them. They cannot respond…they can’t do anything that would suggest to anyone that they are there in any way, shape or form.” (14:50)
• One third died, one third survived with recovery, one third relapsed later.

7. Chronic/Post-Encephalitic Syndrome & Neurological Legacy (19:21–23:39)

• Chronic EL often involved “statue” state (now: post-encephalitic parkinsonism).
• Patients could develop mood swings, psychosis, increased libido—or a tendency for “excessive silliness and the use of puns” (20:30).
  • Chuck: “Excessive silliness and the use of puns was an actual symptom…seen over and over again.”
• Key medical point: Resembled Parkinson’s disease, but had distinct features—onset could be sudden, not gradual (22:09).

8. Awakenings – The Medical Miracle (23:39–29:08)

• In the late 1960s, neurologist Oliver Sacks treated chronic EL patients in New York with L-DOPA, a new Parkinson’s drug.
• Patients awakened after decades of “statue” state—depicted in Sacks’ book and the 1990 film Awakenings (Robin Williams/Robert De Niro).
• Josh: “[L-DOPA] brought akinetic Parkinson’s disease patients back to life. If you’ve seen the movie Awakenings, that’s basically a big storyline…” (41:25)
• Some patients experienced a brief recovery, then relapsed into immobility, making for a bittersweet and tragic outcome.

9. Medical Riddles—How Is It Contracted? (29:08–36:25)

• Mystery persists: Contagious or not? Evidence is deeply mixed.
  • Group outbreaks (21 affected in a home) vs. single cases among large families.
  • Environmental toxins ruled out early; infectious origins (virus/bacteria) explored but not proven.
  • Extensive research (nearly 9,000 papers) failed to conclusively link Spanish flu, herpes, or strep as causative agent.
• Josh: “We just don’t know…One of the big ones is, how do you even catch this terrible disease?” (28:12)

Memorable Quotes & Moments

• Notable humor: “Waxy flexibility sounds like an album title…Guided By Voices or somebody.” (Chuck, 14:01)
• On awareness: “They were left to just go back to their frozen statue state again. And don’t forget, there is a great level of consciousness within them when they’re in this state.” (Josh, 43:48)
• On chronic sufferers: “[A patient] knew about Pearl Harbor…about Kennedy’s assassination. She said, ‘Nothing has seemed real since 1926, when I got the encephalitis and came to a stop…’” (Chuck quoting Oliver Sacks’ case, 44:48)

Modern Perspective (46:55–51:33)

• The syndrome disappeared as mysteriously as it arose.
• Only 80 suspected cases in the last 75 years.
• Best current theory: EL is likely an autoimmune disorder, perhaps triggered by viruses like strep, herpes, or something similar that causes the immune system to attack the brain in susceptible individuals.
• Treatment for chronic symptoms sometimes includes L-DOPA and, occasionally, electroconvulsive therapy for psychiatric symptoms.
• Von Economo was nominated thrice for the Nobel Prize due to his work.

Cultural Impact

• The story of Encephalitis lethargica, particularly through Sacks' Awakenings, has become emblematic of medical mysteries—highlighting human consciousness, resilience, and the deep unknowns about the brain.

Timestamps for Key Segments

• Historical context & outbreak: 02:37–06:10
• Symptoms and age range: 06:10–09:28
• Von Economo’s subtypes & waxy flexibility: 09:28–14:24
• Mental awareness—patients trapped inside: 14:24–16:21, expanded at 19:21–23:39
• Chronic syndrome/post-encephalitic parkinsonism: 23:39–29:08
• Awakenings/Oliver Sacks/L-DOPA: 41:25–46:55
• Cultural moment—Awakenings film: 24:12–25:13
• Scientific search for causes: 29:08–36:25
• Modern understanding & theories: 46:55–52:10

Tone & Delivery

Throughout, Josh and Chuck maintain their trademark mix of curiosity, humor, empathy, and a relaxed explanatory style—interspersing their digressions, pop culture asides, and personal reflections to make the harrowing subject relatable and engaging.

Conclusion

• Despite nearly a century of research, EL remains unsolved—a haunting reminder of neurological vulnerability and the limits of current science.
• Josh (epilogue): “It’s so fascinating that you have to stop and remind yourself, this actually happened to people. Then you realize how terrifying the whole thing really is.” (51:33)