ACE2 and infection: This might occur via initial infection of the nasal mucosa and movement from there up the olfactory nerve into the brain.65,66 Alternatively, movement of the S1 part of the spike protein across the blood–brain barrier by transcytosis has been reported,67 and crossing the endothelial cell layer may also occur via infection of monocytes (which express ACE2 highly68 and can cross endothelial cells) or via breakdown of the blood–brain barrier as a result of cytokines released as a result of lung inflammation.69