Encephalitis lethargica epidemic of 1918–1930

Encephalitis lethargica is a neurological syndrome that causes lethargy, "mask like faces", excess blood in the meninges, and other general neurological symptoms.[4] It was officially recognized as its own disease in 1917, though it is believed to have existed long before that point.[4] It is also known to cause postencephalitic parkinsonism (PEP).[3] Though often thought of as a disease of the past, it is still seen in occasional cases today.[2]

Neurologist Constantin von Economo published a paper in April 1917 describing some of the cases he encountered in the winter months of 1916–1917.[3] These patients, despite varying diagnoses, had a similar pattern of symptoms which led von Economo to suggest a novel disease, which he called Encephalitis Lethargica.[3]

In France, physician Jean-René Cruchet was experiencing something similar, and he published his findings within a few days of von Economo.[3] After these two, many more reports began being released about the disease, starting in Europe before moving around the globe.[4]

In the United States the epidemic peaked from 1920 to 1924.[1] It is estimated that as many as one million people were diagnosed with Encephalitis Lethargica during the epidemic period.[4]