METHODS: We searched the PubMed and Google Scholar on 15th May 2020, with search terms including SARS-COV-2, coronavirus, COVID-19, hyposmia, anosmia, ageusia and dysgeusia. The articles included were cross sectional studies, observational studies and retrospective or prospective audits, letters to editor and short communications that included a study of a cohort of patients. Case reports, case-series and interventional studies were excluded.

DISCUSSION: A total of 16 studies were selected. Incidence of smell and taste dysfunction was higher in Europe (34 to 86%), North America (19 to 71%) and the Middle East (36 to 98%) when compared to the Asian cohorts (11 to 15%) in COVID-19 positive patients. Incidence of smell and taste dysfunction in COVID-19 negative patients was low in comparison (12 to 27%). Total incidence of smell and taste dysfunction from COVID-19 positive and negative patients from seven studies was 20% and 10% respectively. Symptoms may appear just before, concomitantly, or immediately after the onset of the usual symptoms. Occurs predominantly in females. When occurring immediately after the onset of the usual symptoms, the median time of onset was 3.3 to 4.4 days. Symptoms persist for a period of seven to 14 days. Patients with smell and taste dysfunction were reported to have a six to ten-fold odds of having COVID-19.