Both Covid-19 and common cold patients lose their sense of taste and smell but study finds key differences

These findings could help in developing smell and taste tests for fast Covid-19 screening in emergency departments or at airports


                            Both Covid-19 and common cold patients lose their sense of taste and smell but study finds key differences
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Both Covid-19 and a common cold can block your sense of smell and taste. But how do you tell them apart? According to a new study, there are some key differences. These findings could help build smell and taste tests for fast Covid-19 screening in emergency departments or at airports, the researchers said.

In the study, researchers from Europe examined how smell and taste disorders varied in different patients. The study included 30 participants — 10 with Covid-19, 10 with a common cold and 10 healthy people. All participants took part in a smell and taste test to study the differences.

"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," lead researcher Prof Carl Philpott from the University of East Anglia's (UEA) Norwich Medical School, said in a statement. They set out to figure out the differences in smell loss between the new coronavirus infection and cold or a blocked-up nose.

Their analysis showed that Covid-19 patients have a more intense loss of smell. "They were less able to identify smells," Philpott said. Further, these patients do not struggle with nasal congestion, a runny or blocked nose, unlike other respiratory infections. They also lose their ability to detect bitter or sweet tastes. In fact, it was this loss of true taste that seemed to be present in the Covid-19 patients compared to those with a cold," he added.

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Loss of smell and taste from Covid-19 and its links with the brain

All of these differences add weight to the theory that the new coronavirus attacks the brain and the nervous system. "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," Philpott said. 

Some Covid-19 patients have developed symptoms linked to the brain. For instance, some have had a condition known as encephalitis, which is swelling and inflammation in the brain. Other disorders such as delirium, impaired consciousness and stroke are also connected with the disease. "Our results reflect, at least to some extent, a specific involvement at the level of the central nervous system in some Covid-19 patients," he noted.

The researchers hope to understand if some versions of genes could make some people more vulnerable to the loss of smell and taste. "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."
 
Still, the results open avenues for developing screening tools. "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."

The study is published in Rhinology.

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