Single-cell RNA sequencing revealed that only sustentacular cells and horizontal stem cells in the olfactory cleft, as well as the vascular pericytes in the olfactory bulb, co-express ACE2 and TMPRSS2, which explains why the local infection of these cells may cause a block of odor conduction, indicating that general disturbance of the mucosal architecture can obstruct the processing and signal transmission to the brain [99]. Here, TMPRSS2 is linked to infection.