The study will be a retrospective-prospective, longitudinal case-control observational study using a convenience sample drawn from patients presenting for COVID-19 screening, and will recruit both males and females above the age of 21 years who consent to provide anonymised data online on recent changes to their taste and smell. There will be no intervention (medication or foods) as part of this study. Potential participants will be screened to ensure they meet the study inclusion and exclusion criteria and all participants will sign an informed consent.

During their first recruitment session at the hospital/clinic, participants will be required to complete a series of questionnaires to record recent changes in taste and smell sensitivity. The series of questionnaires will include: Singapore Smell and Taste Questionnaire (SSTQ), Sino-nasal Outcome Test-22 (SNOT-22) and optionally, the Global Consortium of Chemosensory Research Questionnaire (GCCRQ). The purpose of administering the different questionnaires is to cover wide range of complementary questions that capture information related to changes in taste and smell function associated with COVID-19 infection. Thereafter participants will be briefed on how to complete the home-use standardized smell and taste test (Home-use Test). The Home-use Test (HUT) will be completed daily over a 28 day period at participants place of residence, to enable self-monitoring of changes to smell and taste abilities. During the HUT, participants will rate their sense of smell using the two standardised odour pens they are provided on the first day of their session at the hospital/ clinic. For each pen, participants will be asked to identify the odour and rate the perceived intensity. This will then be followed a taste test where participants will take a small quantity of a powder representing each of the four prototypical basic tastes sweet (sugar), salt (table salt), bitter (coffee powder or tea) and sour (lime powder), to the tip end of their tongue with a small spoon to taste. Participant are asked to self-report that they confirm that can identify the taste quality and to rate the perceived intensity on line scales provided in an online questionnaire. All measures are self-administered and completed independently by the participant, with responses captured using unique identifier code for each participant through an online software (CompuSense, Guelph, Ontario). During the 28-day home use test period, once a week participants will be asked to complete a 'Follow-up Questionnaire' which will assess how the symptoms experienced have impacted their enjoyment of food, appetite and food-related quality of life.