Fig. 3
From: COVID-19 and Alzheimer’s disease: how one crisis worsens the other
Potential routes of SARS-CoV-2 invasion into the CNS. Based on the tissue/cell expression patterns of the viral binding receptor ACE2 and cell entry-associated proteases TMPRSS2 on the olfactory epithelium, myelin-forming cells, enteric neurons, and vascular endothelium, it is plausible that SARS-CoV-2 enters the human brain via the neural route of myeline sheaths of olfactory, enteric and vagal nerves, and via the hematogenous route across the blood-brain barrier