Respiratory viral infections and associated neurological manifestations

Respiratory viruses as a major threat to human and animal health today are still a leading cause of worldwide severe pandemics. Although the primary target tissue of these viruses is the lung, they can induce immediate or delayed neuropathological manifestations in humans and animals. Already after the Spanish flu (1918/20) evidence accumulated that neurological diseases can be induced by respiratory viral infections as some patients showed parkinsonism, seizures, or dementia. In the recent outbreak of COVID-19 as well patients suffered from headache, dizziness, nausea, or reduced sense of smell and taste suggesting that SARS-CoV2 may affect the central nervous system (CNS). It was shown that different respiratory viral infections can lead to deleterious complications in the CNS by a direct invasion of the virus into the brain and/or indirect pathways via proinflammatory cytokine expression. Therefore, we will discuss in this review mechanisms how the most prevalent respiratory viruses including influenza and coronaviruses in humans can exert long-lasting detrimental effects on the CNS and possible links to the development of neurodegenerative diseases as an enduring consequence