Encephalitis lethargica, or the 'sleepy sickness', swept the globe between 1916 and 1927, infecting over a million people and claiming 500,000 lives. The cause remains unknown, and the disease vanished as suddenly as it appeared, leaving medical experts puzzled to this day.
The illness often started with flu-like symptoms before progressing to extreme lethargy, double vision, and a sleep-like state that could last months. Disturbingly, patients were not truly asleep but fully conscious, trapped inside their bodies while their minds remained active.
About one-third of sufferers died from respiratory complications during the acute phase, another third recovered, and the final third faced debilitating neurological effects. Some developed post-encephalitic parkinsonism, a degenerative brain condition causing stiffness and immobility, while others experienced profound personality changes, including impulsivity and violence.
Young victims were particularly affected, becoming increasingly uncontrollable and sometimes dangerous as they grew. The disease could turn previously calm children into aggressive individuals, with some engaging in self-harm.
Despite its severity, encephalitis lethargica remains a medical mystery. It emerged concurrently with the Spanish Flu pandemic, leading to speculation of a link, but no consensus was reached. The sudden disappearance of the epidemic has only deepened the enigma surrounding this strange and terrifying illness.
