Review of taste and taste disturbance in COVID-19 patients.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic that has become a significant global public health concern. The virus gains entry to cells via angiotensin-converting enzyme-2 (ACE2) receptors, which have been found to be the functional receptor for SARS-CoV-2 infection. High expression of ACE2 is found in type II alveolar cells, macrophages, bronchial and tracheal epithelial cells and in the oral cavity, particularly on the tongue. Taste disturbance is one of the early symptoms of COVID-19, suggesting that taste cells in taste buds are vulnerable to SARS-CoV-2 infection. Taste is modulated by hormones that are regulated in the renin-angiotensin-aldosterone system. Hypothetical causes of taste disturbance by SARS-CoV-2 may be due to direct cell and/or neuronal injuries, inflammatory responses and dysregulation of ACE2.