The exact cause of this condition is unclear, but scientists believe it is due to damage to the olfactory epithelium (cells in part of the nose), which protects the olfactory nerve, help people smell the surroundings.
According to Dr. Justin Turner, associate professor of otolaryngology at Vanderbilt University, early data suggests that the cells that support the olfactory epithelium are the main cells that infect the virus. It is possible that this causes nerve cell damage. However, researchers still don’t know why and when it happens, and why it’s more common in certain patients.
Research published in the journal Nature Genetics on January 17 explains that. According to scientists, a genetic site near two olfactory genes is linked to the inability to smell scents after Covid-19 . This is the fixed position of the chromosomal gene.
That genetic factor increases the odds of post-Covid-19 loss of smell or taste by 11% . It is estimated that 4 out of 5 patients will regain their senses. However, the researchers warn that the condition can prolong or permanently reduce the ability to smell, affecting the physical and psychological well-being of patients.
The study was carried out by scientists at the biotech and genetics company 23andMe in the US and UK. Of the nearly 70,000 volunteers who had been infected with Covid-19, 68% reported having had sequelae of loss of taste and smell.
When comparing the genetic differences between the volunteers, the team found a genomic region that explains the condition, called UGT2A1 and UGT2A2. Two genes play a role in the metabolism of odorants.
“This is a really cool scientific example. Starting with people who were already involved in the study, we were able to quickly gain a biological understanding of the disease,” said Adam Auton, deputy head of genetics humans at 23andMe, the study authors said.
Experts are not sure how the odorants of UGT2A1 and UGT2A2 are metabolized. Auton and colleagues hypothesized that the two genes “play some role in the physiology of infected cells” and lead to loss of smell.
To further learn from this finding, scientists need to learn more about the genes that are expressed and their function in olfactory signaling, Turner said.
The study also showed that women are 11% more likely to experience this sequelae than men. Adults between the ages of 26 and 35 made up 73% of the group with loss of smell.
In addition, the experts found that East Asian Americans or African Americans had lower rates of loss of smell or taste. The researchers say the cause of this condition is still unclear, and note that the study’s data are limited, because they only focused on people of European ancestry.
Danielle Reed, deputy director of the Monell Chemical Senses Center, said the new discovery could assist patients with sequelae in two ways. First, it helps answer the question “why some people experience this symptom and some don’t”. It also helps scientists learn about treatments for this condition.
Previous work has shown that taste loss is caused by damage to the sensory neurons of the nose and tongue following nCoV infection. “This study suggests a different direction. It points to factors that disrupt the chemical messengers of taste that can fake the ability to taste or distort scents,” Ms. Reed said.
During the pandemic, loss of taste and smell is considered the hallmark symptom to distinguish the disease. Initial assessment shows that Omicron is less likely to cause this condition, but the incidence is not zero. In a study of 81 Omicron-infected F0 in Norway, 12% reported impaired taste and 23% progressive loss of taste.