The Loss of Smell and Taste in the COVID-19 Outbreak: a Tale of Many Countries

Abstract

Purpose of review: Olfactory dysfunction in upper airway viral infections (common cold, acute rhinosinusitis) is common (> 60%). During the COVID-19 outbreak, frequency of sensory disorders (smell and/or taste) in affected patients has shown a high variability from 5 to 98%, depending on the methodology, country, and study.

Recent findings: A sudden, severe, isolated loss of smell and/or taste, in the absence of other upper airway inflammatory diseases (allergic rhinitis, chronic rhinosinusitis, nasal polyposis), should alert individuals and physicians on being potentially affected by COVID-19. The evaluation of smell/taste disorders with a visual analogue scale or an individual olfactory or gustatory test, at the hospital or by telemedicine, to prevent contamination might facilitate an early detection of infected patients and reduce the transmission of SARS-CoV-2. During the COVID-19 outbreak, patients with sudden loss of smell should initiate social distancing and home isolation measures and be tested for SARS-CoV-2 diagnostic test when available. Olfactory training is recommended when smell does not come back after 1 month but can be started earlier.

Keywords: Acute rhinosinusitis; Anosmia; COVID-19; Hyposmia; SARS-CoV-2; Smell and taste dysfunction.

Fig. 1

High variability in the frequency/incidence of loss of smell (from 5 to 98%) in studies and surveys conducted across different countries from Asian, European, and American regions during the COVID-19 outbreak. Study first authors and corresponding countries are displayed in the Y axe legend. In international studies: single asterisk indicates studies/surveys were performed in France, Belgium, Italy, and Spain; double asterisks indicate studies/surveys were performed in the USA, Mexico, Italy, and UK; triple asterisks indicate studies/surveys were performed in France, Belgium, Italy, Spain, and Switzerland