Back to the future: lessons from past viral infections and the link with Parkinson's disease.

During the current coronavirus disease 2019 (COVID-19) pandemic, there has been noticeable increase in the reporting of neurological symptoms in patients. There is still uncertainty around the significance and long-term consequence of these symptoms. There are also many outstanding questions on whether the causative virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) can directly infect the central nervous system (CNS). Given the long association between viral infections with neurodegenerative conditions such as Parkinson's disease (PD), it seems timely to review this literature again in the context of the COVID-19 pandemic and to glean some useful information from studies on similar viruses. In this commentary, we will consider the current knowledge on viral infections in the brain. In addition, we review the link between viral infection and neurodegeneration in PD, and review the recent literature on SARS infections, the potential link with PD and the potential areas of study in the future.