Loss of smell from COVID-19 may be due to genetics: US study

A new study reveals that the loss of smell caused by Covid-19 might be due to a hereditary risk factor. While the exact origin of sensory loss caused by Covid-19 is unknown, scientists believe the virus destroys cells in the olfactory epithelium, which is a component of the nose.

Olfactory neurons, which help people smell, are protected by cells in this area of the nose. Researchers in the United States studied the genetic variations between persons who tested positive for Covid-19 and lost their sense of taste or smell and those who did not, using data from genomics testing firm 23andMe.

They discovered a region near two genes, UGT2A1 and UGT2A2, which is the precise location of a gene on a chromosome. The olfactory epithelium expresses the UGT2A1 and UGT2A2 genes. They have an impact on how we process odours.

Experts said that those who have this genetic region are more susceptible to lose their sense of smell. The exact involvement of UGT2A1 and UGT2A2 in the process is unknown, but according to the study, these genes may play a role in the physiology of infected cells and the resultant functional impairment that contributes to loss of capacity to smell.

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‘It was this really beautiful example of science where, starting with a large body of activated research participants who have done this 23andMe test, we were able to very quickly gain some biological insights into this disease that would otherwise be very, very difficult to do’, Adam Auton, vice president of human genetics at 23andMe and the lead author of the study said.

In May 2020, the United Kingdom recognised a loss of smell or taste as a symptom of Covid-19. Covid-19 was found in all 69,841 participants who took part in the research, and 68% of them reported a loss of smell or taste.
Women were more likely than males to experience a loss of taste or smell, with 72 percent reporting it compared to 61 percent of men.

Furthermore, those of East Asian or African American ancestry are less likely to report a loss of smell or taste, according to researchers.