-The highest levels of viral RNA and S proteins for SARS-CoV-2 were found within the olfactory mucosa sampled directly beneath the cribriform plate, as compared to other regionally defined tissue samples, indicating the area as an entry point.

-Proximity of neurons, nerve fibers and mucosa within the oro- and nasopharynx and the reported clinical–neurological signs related to altered smell and taste perception suggest that the neural–mucosal interface is exploited as a port of entry into the CNS.

-Local CNS infection was identified by HLA-DR+ inflammatory response in the CSF, with increased levels of inflammatory mediators such as interleukin (IL)-6.

Figure: Various SARS-CoV-related investigations of the individuals who tested positive for SARS-CoV-2 by RT–qPCR in the olfactory mucosa (OM), the CNS or both. SARS-CoV-2 RT–qPCR positivity was combined with results derived from SARS-CoV-specific immunohistochemistry (IHC) and ISH as well as EM in appropriate tissue as available.