Reports and studies from various countries around the world have indicated that many COVID-19 survivors may continue to experience the loss of smell and taste for several months after recovery. It is noted that the currently dominant Omicron variant does not usually lead to the loss of these senses, and its symptoms are generally mild and resemble those of the flu.
In an attempt to explain the loss of smell and taste following COVID-19 infection, scientists have identified a "genetic factor" that may pave the way for finding an appropriate treatment for this persistent symptom. An NBC News report highlighted a study published in the journal Nature Genetics, stating that "approximately six months after contracting the virus, 1.6 million people in the United States remain unable to smell or have experienced changes in their sense of smell."
The scientists involved in the study, organized by a genomics and biotechnology company and including participants from the United States and the UK, believe that the precise reason for the loss of these senses is due to damage to infected cells in a part of the nose known as the olfactory epithelium. Dr. Justin Turner, an assistant professor of otolaryngology at Vanderbilt University who was not part of the study, remarked: "How do we move from infection to loss of smell? It is still unclear." He added, "Early data suggest that the virus targets the supporting cells of the olfactory epithelium, leading to the death or damage of the nerve cells within it, but we really do not know why this occurs in certain individuals."
According to the study, the loss of senses is linked to a genetic location for smell and taste on a chromosome. This genetic risk factor increases the chances of a virus-infected person losing their sense of smell or taste by 11%. Some estimates indicate that 4 out of every 5 COVID-19 patients regain these senses.
Among a group of 69,841 individuals who reported a positive COVID-19 test, 68% of them reported a loss of smell or taste. By comparing the genetic differences between those who lost their sense of smell and those who did not, the study team identified a region in the genome associated with this phenomenon, specifically the UGT2A1 and UGT2A2 genes.
To use these findings for treatment development, scientists need to learn more about how these genes are expressed and their functions in sensory activation. The study also revealed that women are 11% more likely than men to experience a loss of smell and taste, while adults aged 26 to 35 represent 73% of this group.
Since its emergence in China in December 2019, COVID-19 has caused the deaths of at least 5,537,051 people worldwide. The United States has recorded the highest number of virus-related fatalities, totaling 850,605, followed by Brazil (621,045), India (486,451), and Russia (321,990). The World Health Organization estimates that the total number of deaths may be two to three times higher, taking into account the excess deaths attributed to the pandemic.
