Changes in taste and smell as symptoms of COVID-19
1 June 2020. Related: COVID-19: pathogenesis, COVID-19.
Simon Collins, HIV i-Base
On 20 April 2020, based on accumulated evidence, the i-Base Q&A service included information about changes and taste being a common symptom of COVID-19. 
Early anecdotal reports in the US also included taste and smell changes and this was now supported by a published study that confirmed these as symptoms. 
The US study reported that smell and taste loss were reported in 68% (40/59) and 71% (42/59) of people who had COVID-19, respectively. This compared to only 16% (33/203) and 17% (35/203) of people that did not have COVID-19. People reporting smell and taste changes were about ten times more likely to have COVID-19.
Two other studies have reported more details. [3, 4]
The letter in JAMA reported that taste and smell changes occurred in about 1 in 3 people with coronavirus. Also, that this could occur at any time – ie before or after other symptoms. In a few people (about 3%) this was the only symptom of coronavirus.
Approximately a month later the UK government also added changes in taste and smell as key symptoms that would enable someone to test for COVID-19. 
Other papers have since confirmed these symptoms as common. 
- i-Base Q&A. Are taste and smell changes common with COVID-19?
- Yan CH et al. Association of chemosensory dysfunction and Covid-19 in patients presenting with influenza-like symptoms. International Forum of Allergy & Rhinology, 2020; DOI: 10.1002/alr.22579.
- Giacomelli A et al. Self-reported olfactory and taste disorders in SARS-CoV-2 patients: a cross-sectional study. Clin Infect Dis. 2020;ciaa330. Published online March 26, 2020. doi:10.1093/cid/ciaa330. (26 March 2020).
- Spinato G et al. Alterations in smell or taste in mildly symptomatic outpatients with SARS-CoV-2 infection. JAMA, research letter. (22 April 2020).
- gov.uk. Everyone in the United Kingdom with symptoms now eligible for coronavirus tests (18 May 2020)
- Mercante G et al. Prevalence of taste and smell dysfunction in coronavirus disease 2019. JAMA Otolaryngol Head Neck Surg. DOI:10.1001/jamaoto.2020.1155. (18 June 2020).