ABSTRACT
@#and taste loss were early subclinical symptoms of COVID-19patients. The objective of this review was to identify theincidence of smell and taste dysfunction in COVID-19,determine the onset of their symptoms and the risk factorsof anosmia, hyposmia, ageusia or dysgeusia for COVID-19infection.Methods: We searched the PubMed and Google Scholar on15th May 2020, with search terms including SARS-COV-2,coronavirus, COVID-19, hyposmia, anosmia, ageusia anddysgeusia. The articles included were cross sectionalstudies, observational studies and retrospective orprospective audits, letters to editor and shortcommunications that included a study of a cohort ofpatients. Case reports, case-series and interventionalstudies were excluded. Discussion: A total of 16 studies were selected. Incidence ofsmell and taste dysfunction was higher in Europe (34 to86%), North America (19 to 71%) and the Middle East (36 to98%) when compared to the Asian cohorts (11 to 15%) inCOVID-19 positive patients. Incidence of smell and tastedysfunction in COVID-19 negative patients was low incomparison (12 to 27%). Total incidence of smell and tastedysfunction from COVID-19 positive and negative patientsfrom seven studies was 20% and 10% respectively.Symptoms may appear just before, concomitantly, orimmediately after the onset of the usual symptoms. Occurspredominantly in females. When occurring immediately afterthe onset of the usual symptoms, the median time of onsetwas 3.3 to 4.4 days. Symptoms persist for a period of sevento 14 days. Patients with smell and taste dysfunction werereported to have a six to ten-fold odds of having COVID-19.Conclusion: Smell and taste dysfunction has a highincidence in Europe, North America, and the Middle East.The incidence was lower in the Asia region. It is a strong riskfactor for COVID-19. It may be the only symptom and shouldbe added to the list of symptoms when screening for COVID-19.KEYW