[Smell and Taste Dysfunctions owing to COVID-19]

Olfactory and taste dysfunctions are characteristic symptoms of coronavirus disease 2019 (COVID-19); however, their frequencies and pathogeneses keep changing because of rapid mutations of the viral strains. Angiotensin-converting enzyme 2, a receptor for the spike protein of SARS-CoV-2 in the olfactory epithelium, is involved in the development of olfactory dysfunction. In general, olfactory dysfunctions resolve in a few weeks. However, there are cases wherein the symptoms persist for several months or longer, and parosmia or phantosmia affects the patient's quality of life. It is also assumed that the damage owing to COVID-19 extends to olfactory nerve cells, resulting in sensorineural olfactory dysfunction similar to post-infectious olfactory dysfunction.