Mysterious illness : Encephalitis Lethargica
I have always been intrigued by mysterious illnesses. Even as medicine progresses it is still difficult to assess everything surrounding an illness. The most frustrating part is not being able to find the solution. People would be permanently affected or die unexpectedly. Based on my research, that is the case with the epidemic of Encephalitis Lethargica.
What is Encephalitis Lethargica ?
It was a neurological disease characterized by extreme lethargy, fever, and a coma-like state. It seems to have affected millions from 1917 to 1930. Many died while others were left with permanent mental or physical damage. It is said that Encephalitis Lethargica would appear after a person exhibited flu like symptoms. Individuals would fall in a deep sleep that would go on for days. Some would lose consciousness or manifest oculogyric crises. Other signs include Parkinson’s and personality changes.
What happened after?
By the 1930s, Encephalitis Lethargica disappeared, leaving behind destruction. It later appeared to have lost the medical community’s attention. It was then believed that this disease came from the body’s immune reaction to an infection like influenza. However, nothing was concluded, especially the causes.
The last known survivor on record was Philip Leather. He died at the age of 82 in 2002. He was first diagnosed with Encephalitis Lethargica at the age of 11 when he was admitted to a mental hospital where he remained until he died. He was unable to move and was aware of his surroundings.
It is important to remember that such disease existed. It probably has taken a new form. Maybe today’s medicine might solve the mystery. We can only hope.
References
Rosen D. Asleep: the Forgotten Epidemic That Remains One of Medicine's Greatest Mysteries. J Clin Sleep Med. 2010 Jun 15;6(3):299. PMCID: PMC2883045.
Encephalitis Lethargica: A Mysterious Neurological Disease. Emily Lecea. Dec 5,2025.https://asm.org/articles/2025/december/encephalitis-lethargica-a-mysterious-neurological
