PURPOSE: The sudden onset of smell and taste loss has been reported as a symptom related to COVID-19. There is urgent need to provide insight to the pandemic and evaluate anosmia as a potential screening symptom that might contribute to the decision to test suspected cases or guide quarantine instructions.
METHODS: Systematic review of the PubMed/Medline, Cochrane databases and preprints up to May 3, 2020. Combined search terms included: "COVID-19", "SARS-CoV-2", "coronavirus", "nose", "anosmia", "hyposmia", "olfactory loss", "smell loss", "taste loss", and "hypogeusia".
RESULTS: Our search identified 18 reviewed articles and 6 manuscript preprints, including a large epidemiological study, four observational case series, five case-controlled studies, five cross-sectional studies, five case series of anosmic patients and four electronic surveys. Great methodological differences were noted. A significant prevalence of anosmia is reported in COVID-19 patients. Controlled studies indicate that anosmia is more common in COVID-19 patients than in patients suffering from other viral infections or controls. Most of the studies reported either smell loss or smell plus taste loss. Less severe COVID-19 disease is related to a greater prevalence of anosmia. A quick recovery of the smell loss may be expected in most COVID-19 cases.
CONCLUSION: Anosmia is more prevalent in COVID-19 patients than in patients suffering from other respiratory infections or controls.