 Title page ofEncephalitis Lethargica, Economo, 1931 | |
| Deaths | 20% mortality |
|---|---|
Theepidemic ofencephalitis lethargica lasted from around 1918 to 1930.[1] The cause is still unknown.[2] Though the cause was once attributed to the coincidingSpanish flu epidemic, modern research has disputed this claim.[3] The mortality was as high as 20%.[4]
The epidemic is thought to have started inRomania during 1915, and the disease supposedly spread through the movement of the various troops duringWorld War I. In 1917, it reached theepidemic status inVienna, where it was first described. Disease outbreaks of encephalitis were first reported in England and France during 1918, followed by Canada,Central America, India, and the United States in 1919. Disease outbreaks were also reported in Germany and theSoviet Union during 1920. The epidemic peaked between 1920 and 1929, with an estimated one million people diagnosed with encephalitis lethargica during the epidemic period. The disease suddenly disappeared in the beginning of the 1930s.
In the aftermath of the epidemic, many cases of post-encephalitic parkinsonism were reported. This condition was distinctive fromidiopathic Parkinson's disease, as it occurs in younger patients than typical idiopathic Parkinson's disease, and lacks the "pill-rolling tremor" of idiopathic Parkinson's disease.
Encephalitis lethargica is a neurological syndrome that causes lethargy, a "mask like" face, excessive blood in the meninges, and other generalneurological symptoms.[5] Officially recognized as its own condition in 1917, it is believed to have existed far longer in human history.[5] It is known to causepost-encephalitic parkinsonism.[3]
According to Urechia (1921), the pandemic possibly started in 1915, Romania. It is believed that the disease spread through the movement of the troops duringWorld War I.[6] In 1917, it reached theepidemic status inVienna, where it was first described.[6][7] It was followed by France and England in 1918. In 1919, the disease was present inEurope, theUS,Canada,Central America, andIndia.[6] In 1920, the disease was present in theSoviet Union andGermany.[8]
NeurologistConstantin von Economo published a paper in April 1917 on six cases he encountered in the winter months of 1916 and 1917 in the Psychiatric-Neurological Clinic of theUniversity of Vienna.[3][8] These patients, despite their various previous diagnoses, had a similar pattern of symptoms. This led him to suggest a novel disease, which he named Encephalitis lethargica.[3] In France, physicianRené Cruchet was encountering similar patterns, and published his findings within a few days of Constantin von Economo. Following these two reports, many more cases were reported, first in Europe, but quickly spreading around the globe.[3] Reviews from both works considers Economo as the first to describe the disease, while Cruchet reported a group of heterogeneous conditions.[8] Initially,encephalitis lethargica main symptoms were described assomnolence andlethargy, but after 1919 cases ofinsomnia andhyperkinesia appeared. Economo also describedhiccups as a symptom, which was later linked to the hyperkinetic–insomniac variety ofencephalitis lethargica, but no case between 1920 and 1930 showed this symptom.Endocrine symptoms, such asdiabetes, were only present in cases described between 1922 and 1923.[8]
Following von Economo description of the disease, many speculated that it had the same cause as theSpanish flu. Many poorly conducted experiments pointed to that hypothesis, but in 1923Simon Flexner highlighted the problems with the investigations.[9]
William Matheson founded the Matheson Commission in 1927, promising to find a cure to encephalitis lethargica within two years. They worked with two main hypothesis, that encephalitis lethargica was a form ofherpes or it was a focal infection resulting from a neurotropic form ofStreptococcus viridans. The commission ended in 1940 without finding the cure, but it produced data about the disease.[6]
The epidemic peaked between 1920 and 1929,[1] with an estimated million people diagnosed with encephalitis lethargica during the epidemic period.[5] In the beginning of 1930s, the disease suddenly disappeared, and the attention of the medical community changed to more pressing matters.[10] During the pandemic, approximately 9000 papers about encephalitis lethargica were published.[6]
The causes of encephalitis lethargica are still unknown.[3] Though the connection to the Spanish flu epidemic is often made, the encephalitis outbreak did begin slightly earlier. However, this cannot disprove the claim, simply point out that not all of the existing evidence lines up.[3]
In the aftermath of the epidemic, many cases of post-encephalitic parkinsonism were reported. This condition was distinctive fromidiopathic Parkinson's disease, as it occurs in younger patients than typical idiopathic Parkinson's disease, and lacks the "pill-rolling tremor" of idiopathic Parkinson's disease.[3]
Estimates of the number of people infected varies greatly, from a thousand to a million. The estimated mortality varies between 15% and 40%.[8] It is estimated that 50–75% of cases went unreported. At the same time, the number of reported cases may have been inflated byoverdiagnosis due to the description of generic symptoms and lack of established diagnostic criteria.[6]
BothSandmancomic books andseries depict the epidemic. In the story,Dream is locked against his will, thus causing his realm to collapse and the epidemic to start.[11]
The after effects of the pandemic are addressed in the filmAwakenings.