How loss of smell and taste could be symptoms of COVID-19

A new study gives weight to emerging evidence that a loss of smell and taste is a common symptom of COVID-19—according to University of East Anglia (UEA) smell expert Prof Carl Philpott.

The study, from Kinds College London, looked at responses from more than 400,000 people reporting suspected COVID-19 symptoms via an app.

It found that 59 percent of 579 people who said they had tested positive for the virus reported a loss of smell or taste.

But loss of smell and taste are also signs of other infections, such as the common cold.

Prof Philpott, from UEA's Norwich Medical School, said: "Coronaviruses have been associated with what we refer to as post-viral olfactory loss previously—this is smell loss that persists after a cold. There are many respiratory viruses that can potentially cause problems with the smell receptors.

"So far with COVID-19, the smell loss appears to be transient but only as time elapses will we know how many people have a more permanent loss."

"This latest research from Kings College London give some further weight to the emerging evidence that loss of smell, and perceived loss of taste, is a common symptom in those infected with COVID-19.

"It takes a snapshot of data over one week from self-reporting volunteers who have used the RADAR COVID-1 app.

"It is certainly helpful data to reinforce the call for the World Health Organisation and Public Health England to add this symptom as a warning sign for individuals to self-isolate."

Prof Philpott has recently written for The Conversation about how a sudden loss of smell and taste could be an early symptom of COVID-19.

But he warns that the new data is limited by a number of factors.

"Those who were tested for COVID-19 represent 0.1 percent of the cross-section examined which leads one to ask—what is the true denominator?

"There is also no data on timing and severity of this symptom, and this is only a snapshot over one week. Finally, the reported demographics don't tell us about the geography of respondents—are they all city dwellers or based in London?

"Nonetheless, this report does help to add to the prior data from countries like China and Italy that smell loss must be taken more seriously as a tool for identifying COVID-19 positive patients who may otherwise be unaware or have mild symptoms.

"With emerging evidence about the mechanism of smell loss in COVID-19 and the Global Consortium for Chemosensory Research about to launch an international survey of smell loss related to COVID-19, there is likely to be greater certainty about smell loss as a harbinger of the virus and whether it can be used in isolation, or how the timing of its onset relates to the course of the infection and its severity.

"With viral shedding highest in the nose, it is not surprising that the 'unprotected' smell receptor tissue at the top of the nose is vulnerable to infection," he added.

Another interesting point in the study according to Prof Philpott, is the fact that smell loss appears to be reported by a higher proportion of women.

He said: "This is commonly seen in a specialist smell and taste clinic where a ratio of 2:1 female to male patients is typically seen and women appear more troubled by smell loss than their male counterparts."

Prof Philpott's research has previously revealed how smell loss impacts people's lives.