How Covid-19 smell loss differs from the common cold
Loss of smell and taste is more severe in Covid-19 patients than in patients with common colds and that could be due to the effect the coronavirus has on the brain and nervous system, British researchers reported.
New research from a European group of smell disorder experts, including Prof Philpott at the University of East Anglia, shows how smell loss associated with Covid-19 infection differs from what you typically might experience with a bad cold or flu.
The new study is the first to compare how people with Covid-19 smell and taste disorders differ from those with other causes of upper respiratory tract infections.
The main differences found are that, although Covid-19 patients also lose their sense of smell, they can breathe freely, do not tend to have a runny or blocked nose, and they cannot detect bitter or sweet tastes.
These findings lend weight to the theory that Covid-19 infects the brain and central nervous system.
The loss of smell and taste is a prominent symptom of Covid-19, however it is also a common symptom of having a bad cold. We wanted to find out exactly what differentiates Covid-19 smell loss with the kind of smell loss you might have with a cold and blocked-up nose.”, lead researcher Prof Carl Philpott, from UEA’s Norwich Medical School, said in a press release.
This research was led by the Cliniques Universitaires Saint-Luc (Belgium), Université catholique de Louvain (Belgium) in collaboration with researchers at University of East Anglia/The Norfolk Smell and Taste Clinic at the James Paget University Hospital (UK), Aristotle University (Greece), Acibadem Taksim Hospital in Istanbul (Turkey), Biruni University (Turkey) and University Hospital of Foggia (Italy).
‘Comparison of COVID-19 and Common Cold Chemosensory Dysfunction’ is published in the journal Rhinology on August 19, 2020.
Smell loss was much more profound in the Covid-19 patents
The research team carried out smell and taste tests on 10 Covid-19 patients, 10 people with bad colds and a control group of 10 healthy people – all matched for age and sex.
“We found that smell loss was much more profound in the Covid-19 patents. They were less able to identify smells, and they were not able to identify bitter or sweet tastes. In fact it was this loss of true taste which seemed to be present in the Covid-19 patients compared to those with a cold.
This is very exciting because it means that smell and taste tests could be used to discriminate between Covid-19 patients and people with a regular cold or flu.
Smell and taste tests
“Although such tests could not replace formal diagnostic tools such as throat swabs, they could provide an alternative when conventional tests are not available or when rapid screening is needed - particularly at the level of primary care, in emergency departments or at airports.
“This research also shows that there are altogether different things going on when it comes to smell and taste loss for Covid-10 patients, compared to those with a bad cold.
involvement at the level of central nervous system
Our results reflect, at least to some extent, a specific involvement at the level of central nervous system in some COVID-19 patients. “It is particularly interesting that Covid-19 seems to particularly affect sweet and bitter taste receptors, because these are known to play an important role in innate immunity.
“More research is needed to see whether genetic variation in people’s bitter and sweet taste receptors might predispose them to Covid-19, or conversely, whether Covid-19 infection changes how these receptors function, either directly or through a cytokine storm – the over-reaction of the body’s immune system”, researcher Prof Carl Philpott comments.