Whilst the classic symptoms of COVID-19 – fever, persistent dry cough, shortness of breath – are now drummed into anyone following the spread of this novel coronavirus, a potential new symptom has begun to be reported by medical experts – a loss of smell or taste.
This was highlighted recently in a report by two senior ear, nose and throat (ENT) specialists in London, Claire Hopkins and Nirmal Kumar. Hopkins is president of the British Rhinological Society and Kumar is the president of ENT UK.
“While further research is required, loss of smell, or anosmia, has been reported in as many as 1 in 3 patients in South Korea and, in Germany, this figure was as high as 2 in 3 patients,” said Simon Carney, a professor of otolaryngology (head and neck surgery) at Flinders University, in a press release.
Damage to olfactory neurons
Impairment of our sense of smell is a common symptom of having a viral infection, such as a cold or influenza, because these viruses invade our upper respiratory tract and cause damage to the olfactory receptor neurons that enable us to smell. But previous health advice had not highlighted this symptom in relation to infection with SARS-CoV-2.
Importantly, these reports remain unverified by peer-reviewed research, but speaking to the Science Media Centre, Carl Philpott, a professor of rhinology & olfactology at the University of East Anglia, said, “Coronaviruses have previously been associated with what we refer to as post-viral olfactory loss – 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.”
Asymptomatic carrier risk
Carney expressed concern that individuals with coronavirus-induced anosmia but without other symptoms may be unaware that they are infected. This could represent a potential source of asymptomatic carriers who could be at risk of unknowingly infecting others. In their statement, Hopkins and Kumar highlighted four patients they had seen, all under 40, who had reported sudden anosmia in the last week. The normal rate for such symptoms, they said, was no more than one per month. The patients, with their current symptoms, don’t meet the criteria for testing or self-isolation, but Hopkins and Kumar suggested that by asking adults with sudden-onset anosmia to self-isolate, the rate of viral transmission could be reduced.
Philpott agreed with this recommendation: ““We’re not yet aware yet as to whether this symptom is common or a sign of a poor outcome but certainly recommend a warning sign to self-isolate and if heeded may help to prevent spread.”