New findings on loss of smell and taste when infected with Covid-19

Scientists say that some people lose their sense of smell, as well as taste after contracting Covid-19 may be related to genetic factors.

Six months after contracting Covid-19, up to 1.6 million people in the US still cannot smell or have a disorder of the ability to smell, according to NBC.

The exact cause of the Covid-19-related symptom is still unknown, but scientists think it stems from infected cells in the nasal area, called the olfactory epithelium, being damaged. love. These cells protect the olfactory nerve cells, which help humans smell scents.

"How people with Covid-19 go from being infected to losing their sense of smell is still an open question," said Justin Turner, an associate professor of otolaryngology at Vanderbilt University.

'Preliminary data suggest that the cells that support the olfactory epithelium are the predominant cells infected with viruses. Perhaps this leads to the death of these very neurons,' he said.

"But we don't really know why and when that happens, or why it seems to only happen in certain individuals," he added.

Research published January 17 in the journal Nature Genetics has identified another genetic factor linked to the loss of smell after contracting Covid-19.

This discovery helps experts better understand olfactory dysfunction and possibly find the necessary treatment.

Inherited genes can lead to loss of smell and taste when infected with Covid-19.

Genetic risk

According to new research, a fixed gene location on a DNA molecule (locus gene), located near two olfactory genes, is associated with the loss of smell and taste caused by the corona virus.

Scientists at the biotech and genomics company 23andMe conducted the study as part of a larger project on Covid-19. All volunteers live in the US or UK.

Of the 69,841 people who self-reported as having tested positive for the SARS-CoV-2 virus, 68% reported experiencing a loss of smell or taste.

After comparing the genetic differences between people who lost their sense of smell and those who reported they weren't affected, the team found a region in the genome associated with this difference.

That is the region located near the two genes UGT2A1 and UGT2A2. Both genes are found in tissue in the nose, involved in smell, and play a role in the metabolism of chemicals that send signals from the olfactory receptor to the area of ​​the brain that processes scent.

'(Through research), we quickly gained biological insights into the disease that were difficult to do in the past,' said Adam Auton, vice president of genetics at 23andMe and a lead author of the study, said.

How UGT2A1 and UGT2A2 are involved in the process leading to loss of smell in people with Covid-19 remains unclear. Still, Mr. Auton and colleagues hypothesized that genes 'may play some physiological role in infected cells' and as a result lead to impaired, loss of sense of smell. .

An inherited genetic risk can increase the chance that a person infected with SARS-CoV-2 will lose their sense of smell or taste by 11%.

New research also shows that 4 out of 5 patients who experience this symptom will recover later. However, the condition can lead to long-term loss of smell, or the ability to smell and taste, and affect relationships, physical and psychological health, researchers warn.

Scientists will need to learn more about how these genes are expressed and their function in signaling to the sense of smell, Turner added.

Another direction

The researchers also found certain trends in people with Covid-19, experiencing a loss of smell, taste, or both.

For example, women are 11% more likely to develop this condition than men. Meanwhile, adults aged 26-35 make up 73% of this group.

The team also found that subjects with "East Asian or African ancestry were less likely to have a loss of smell or taste".

The cause of this new finding is still unknown. This may not be due to genetic variations on specific gene sites, says Auton.

However, NBC assessed the study as still having some limitations in terms of grouping the assessment and using self-reported data from the participants.

The team also note that this study was conducted mainly in people with European ancestry, so the reference data is limited.

Danielle Reed, deputy director of the Monell Center for Chemical Sensors, says the findings could help patients in two ways.

First, 'it helps answer the question of why me' when he has lost his sense of smell and taste after contracting Covid-19.

New research could help scientists find treatments for Covid-19 patients who have lost their sense of smell or taste.

'Some people experience this symptom and some don't. Inherited genetics may partly explain why,' she said.

Research can also help scientists find treatments. Previous research has shown that the loss of these senses is linked to 'receptive cells in the nose and tongue becoming infected with a virus,' says Ms Reed.

'This study suggests a different direction,' she said. 'From the very beginning, the metabolic pathways for the perception of smell and taste can be overactive or inactive, reducing or distorting the ability to taste and smell'.

Early research also shows that people infected with the Omicron strain rarely experience loss of smell and taste. However, this does not mean that it does not happen at all. In a study of 81 patients with Omicron infection in Norway, 12% reported impaired taste and 23% reported progressive loss of taste.