Covid Research: Why do some people lose their sense of smell? Scientists answer

Six months after infection by Covid-19, about 1,6 million people in the US still suffer from loss or deterioration of smell

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Because some people lose their sense of smell when they are infected with it Covid-19; Experts gathered data to answer this question and found that the answer has to do with genetic factors.

Η study published Monday in the scientific journal Nature Genetics has identified a genetic factor linked to olfactory loss following Covid infection. This is a discovery that brings experts closer to understanding this complex pattern and may pave the way for possible treatments.

Six months after infection by Covid-19, approximately 1,6 million people in the US still suffer from loss or deterioration of smell. The exact cause remains unknown, but scientists believe it stems from damage to infected cells in a specific area of ​​the nose, also known as the olfactory epithelium. These cells protect the olfactory neurons, which allow humans to recognize odors.

"How we go from infection to olfactory loss remains unclear," he said. Justin Turner, an associate professor of otolaryngology at Vanderbilt University, did not participate in the study.

"Initial data show that the olfactory support epithelial cells are the ones that are most infected with the virus, and this may lead to the death of the neurons themselves," he said. "But we do not really know why and when this happens, and why it seems to happen more to specific people."

A genetic factor close to two olfactory genes is associated with the loss of smell and taste by Covid, according to the study. This factor has to do with the constant position of a gene on a chromosome.

This genetic risk factor increases by 11% the chance that a person infected with coronavirus will experience a loss of smell or taste.

In addition, while some estimates suggest that 4 out of 5 patients with Covid regain these sensations, research shows that persistent weakness or reduced sense of smell and taste affect relationships, physical health and psychological well-being.

The researchers also compared the genetic differences between people who lost their sense of smell from the infection and those who did not show this symptom, and found an area of ​​the genome associated with this separation that is close to two genes, UGT2A1 and UGT2A2. Both of these genes are located in the nasal tissue associated with odor and play a role in odor metabolism.

The study also found that African Americans, or people of East Asian descent, were much less likely to report loss of smell or taste. "The cause is not yet known," said Adam Otto, lead author of the study. The team notes, however, that the study shows a biased picture of the case of people of European descent, due to limited data.

The study's findings can help patients in two ways, says Daniel Reed, deputy director of the Monell Chemical Senses Center, which studies the individual-to-individual differences in olfactory and taste loss due to Covid and does not participated in the new research.

First: "It helps to answer the question 'why me' in terms of the loss of smell and taste from Covid", he explains. "It happens to some and not to others. "Genetic traits may partly explain why."

Second, the study could help scientists find cures. Initial research shows that the loss of these senses is associated with a "failure to protect the sensory cells of the nose and tongue from viral infection," Reed said.

"But this study shows a different direction," he notes. "The pathways that break down the chemicals that cause taste and smell may be dysfunctional or overly functional from the start, reducing or altering the ability to taste and smell."

With information from NBC News