Why COVID-19 patients might lose sense of smell 

When examining how SARS-CoV-2 enters the body, one part of the nose may provide further insights into transmission, symptoms, and potential avenues of treatment for COVID-19, researchers suggested from a lab study of human tissue samples.

ACE2 receptor expression was 200- to 700-fold greater in the olfactory epithelium -- the center of smell detection -- relative to other areas of the nose and trachea, reported Andrew Lane, MD, of Johns Hopkins Outpatient Center in Baltimore, and colleagues. ACE2 is the primary portal through which the SARS-CoV-2 virus enters host cells.

"The olfactory epithelium is quite an easy part of the body for a virus to reach, it's not buried away deep in our body, and the very high levels of ACE2 that we found there might explain why it's so easy to catch COVID-19," co-author Mengfei Chen, PhD, also of Johns Hopkins, said in a statement.