Long-term sequelae of coronavirus disease 2019 (COVID-19) due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are now recognized. However, there is still a lack of consensus regarding the terminology for this emerging chronic clinical syndrome, which includes long COVID, chronic COVID syndrome, post-COVID-19 syndrome, post-acute COVID-19, and long-hauler COVID-19. In this review, I will use the term "long COVID". A review of the medical history and epidemiology of past pandemics and epidemics in modern literature review identifies common long-term post-infectious disorders, with the common finding of altered cognition. In the brain, the cerebral hypoxia induced by SARS-CoV-2 infection may be caused by mitochondrial dysfunction, resulting in "brain fog". Historically, the common symptom of altered cognition has been reported during earlier pandemics, which include the influenza pandemics of 1889 and 1892 (Russian flu), the Spanish flu pandemic (1918-1919), encephalitis lethargica, diphtheria, and myalgic encephalomyelitis (chronic fatigue syndrome or post-viral fatigue syndrome). There are similarities between chronic fatigue syndrome and the "brain fog" described in long COVID. During past viral epidemics and pandemics, a commonality of neural targets may have increased viral survival by conformational matching. The neurological and psychiatric sequelae of SARS-CoV-2 infection, or long COVID, may have emerged from neural effects that have emerged from an invertebrate and vertebrate virosphere. This review aims to present a historical overview of infections and disorders associated with neurological and psychiatric sequelae that have shown similarities with long COVID.

Center for Cognitive and Molecular Neuroscience 1st Faculty of Medicine Charles University Prague Prague Czech Republic

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Biomedical Perspectives of Acute and Chronic Neurological and Neuropsychiatric Sequelae of COVID-19

HIV, HSV, SARS-CoV-2 and Ebola Share Long-Term Neuropsychiatric Sequelae

Unexplained post-acute infection syndromes

Reassessment of the blood-brain barrier: a potential target for viral entry into the immune-privileged brain

Dysfunctional mitochondrial processes contribute to energy perturbations in the brain and neuropsychiatric symptoms

Editorial: The Pathogenesis of Long-Term Neuropsychiatric COVID-19 and the Role of Microglia, Mitochondria, and Persistent Neuroinflammation: A Hypothesis