Anosmia: Why COVID-19 patients lose their sense of smell?

Anosmia: Why COVID-19 patients lose their sense of smell?

Scientists found the possible reason why coronavirus patients lose their sense of smell, saying it is likely temporary, unlike anosmia caused by other viral infections.

For the majority of COVID-19 patients, anosmia or the loss of sense of smell is among the first symptoms they noticed before cough or fever. The mechanisms that trigger the case, however, is still a mystery for medical professionals.

But recently, scientists from Harvard Medical School introduced a new light as to why coronavirus infection often leads to anosmia.

The science behind anosmia

The study, which was published in Science Advances, suggests that losing one’s smell after contracting SARS-CoV-2—the virus that causes COVID-19 disease—occurs when supporting cells or non-neuronal cell types are infected, rather a neurological condition.

As seen in the journal, the scientists wrote:

“Single-cell sequencing revealed that ACE2 is expressed in support cells, stem cells, and perivascular cells, rather than neurons. […] These finding suggests CoV-2 infection of non-neuronal cell types leads to anosmia and related disturbances in odor perception in COVID-19 patients.”

At first, the researchers focused on two possible theories as to how anosmia happens. One is through olfactory sensory neurons, and the second is through mucus membranes cells found in the nasal cavity.

They then observed that olfactory neurons do not expel the gene that encodes ACE2 receptor protein. Instead, they found it in the cells that provide “metabolic and structural support to olfactory neurons.”

The said observation also implies that the changes in olfactory neural circuits caused by coronavirus is likely a temporary phenomenon. It means that those who lost their smell will eventually (a few weeks) get it back again.

Scientists said the loss of smell is temporary

Coronavirus patients need not worry whether the damage is permanent or not too. As said, the condition is observed to be temporary only.

Anosmia: Why COVID-19 patients lose their sense of smell?

However, some patients took refuge in what people describe as “smell therapy.” While it is a not cure, the founder of a U.K. charity AbScent told Business Insider that her group is now three times larger compared to when COVDI-19 is still unknown—proof that people are anxious about their condition.

“I think it is good news because once the infection clears, olfactory neurons do not appear to need to be replaced or rebuilt from scratch,” said Professor Sandeep Robert Datta, one of the authors of the study.

Yet he added that the community still needs more data to better understand the underlying factors that prompt anosmia.

Still, it is a relief that the damage caused by SARS-CoV-2 is far from what other viral infections can do, which is found to have direct damage in olfactory sensory neurons and typically take months before the patient regain his sense of smell.

Images courtesy of Pixabay, Chris F/Pexels

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