Linkage between SARS-CoV-2 infection and neurodegenerative disorders: Review and current update

The emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002, followed by the Middle East respiratory syndrome coronavirus (MERS-CoV) that causes fatal illness in 2012, has made coronaviruses a public health concern. Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection does not only affect the respiratory system but has also been observed to elicit neurological manifestations, with anosmia and ageusia being the most common, followed by headache, seizures, neuropathies, and encephalopathy. In addition to SARS-CoV and MERS-CoV which have been proven to be neuroinvasive, SARS-CoV-2 has been found to worsen preexisting long-term neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease, apart from triggering the acute neurological symptoms. The association between COVID-19 and relatively rare neurodegenerative disorders such as amyotrophic lateral sclerosis and Huntington’s disease has yet to be corroborated due to limited significant data. Studies have shown that COVID-19 does not seem to exacerbate these disorders, and the severity of COVID-19-related disease and fatalities is not significantly higher in the affected patients than in the general population. However, increased complications have been reported among the patients in advanced stages of these diseases. Hence, it is imperative to conduct long-term, comprehensive investigations on the effects of SARS-CoV-2 on neurodegenerative disorders, with the ultimate aim of developing appropriate interventions. Studies involving larger cohorts of people of varying ages, disease duration, and ethnicity are urgently warranted.