A terrifying illness that swept the globe a century ago, leaving half a million dead, still baffles doctors today. Encephalitis lethargica, known as 'sleep sickness', first emerged in 1916 and vanished just as suddenly a decade later, with only a handful of cases recorded since.
The disease began with flu-like symptoms such as sore throat, cough, and fever, but quickly escalated to double vision and extreme fatigue. Patients would fall into a coma-like sleep for weeks or months, yet remain fully conscious and aware of their surroundings, unable to move or react. Around a third of sufferers died during this phase, often from respiratory complications.
Survivors frequently experienced profound neurological changes. Some became frozen like statues, trapped within their own bodies for life. Others underwent disturbing personality shifts, becoming criminally impulsive or engaging in self-harm, including one patient who gouged out their own eye. Children, in particular, could turn feral, with their brains rapidly degenerating into a condition called post-encephalitic parkinsonism.
Named by Dr Constantin von Economo in 1917, the cause of Encephalitis lethargica remains unknown. Autopsies revealed inflammation at the base of the brain, but no cure or prevention was ever found. The epidemic infected over a million people and coincided with the Spanish Flu pandemic, leading some to suspect a viral link, though this was never confirmed.
