Encephalitis lethargica epidemic of 1918–1930
# Encephalitis lethargica epidemic of 1918–1930

An Encephalitis Lethargica Epidemic took place between 1918 to 1930. It is still unknown what caused this epidemic. Though it used to be believed that it was connected to the Spanish flu epidemic, modern research provides arguments against this claim.

## Background

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

## Timeline

Neurologist Constantin von Economo published a paper in April 1917 describing some of the cases he encountered in the winter months of 1916–1917. 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.

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

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

