New Delhi: As the world battles the novel Coronavirus, researchers have identified how the loss of smell and taste, a key symptom of virus infection of Covid-19, differs from the common cold or flu.

According to a study published in the journal Rhinology, the loss of smell and taste due to Coronavirus is different from what one experiences during common cold and viral infection.

The main difference is understood to be is that in the case of coronavirus, people can breathe freely, may not have running or blocked nose, and their taste buds remain non-functional.

The study in the journal Rhinology 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.

These findings lend weight to the theory that COVID-19 infects the brain and central nervous system.

The research team hopes that their work could help develop smell and taste tests for fast COVID-19 screening – in primary care and emergency departments.

Lead researcher Prof Carl Philpott, from UEA’s Norwich Medical School, said: “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.”

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.

Prof Philpott said: “We wanted to see if their smell and taste test scores could help discriminate between COVID-19 patients and those with a heavy cold. We know that COVID-19 behaves differently to other respiratory viruses, for example by causing the body’s immune system to over-react, known as a cytokine storm, and by affecting the nervous system.”

“So we suspected that patterns of smell loss would differ between the two groups. 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.”

It has previously been suggested that the COVID-19 virus affects the central nervous system, based on the neurological signs developed by some patients. There are also similarities with SARS, which has also been reported to enter the brain, possibly via smell receptors in the nose.

“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,” Philpott said.