Smell and taste dysfunction in patients with SARS-CoV-2 infection: A review of epidemiology, pathogenesis, prognosis, and treatment options.

During the initial pandemic wave of COVID-19, apart from common presenting symptoms (cough, fever, and fatigue), many countries have reported a sudden increase in the number of smell and taste dysfunction patients. Smell dysfunction has been reported in other viral infections (parainfluenza, rhinovirus, SARS, and others), but the incidence is much lower than SARS-CoV-2 infection. The pathophysiology of post-infectious olfactory loss was hypothesized that viruses may produce an inflammatory reaction of the nasal mucosa or damage the olfactory neuroepithelium directly. However, loss of smell could be presented in COVID-19 patients without other rhinologic symptoms or significant nasal inflammation. This review aims to provide a brief overview of recent evidence for epidemiology, pathological mechanisms for the smell, and taste dysfunction in SARS-CoV-2 infected patients. Furthermore, prognosis and treatments are reviewed with scanty evidence. We also discuss the possibility of using "smell and taste loss" as a screening tool for COVID-19 and treatment options in the post-SARS-CoV-2 infectious olfactory loss.