Covid-19. Loss Of Smell Can Be Caused By The Destruction Of Nasal Cells
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Millions of people around the world who have lost their sense of smell after contracting covid-19 may have an abnormal and continuous immune response that destroys cells in the nose, concluded a group of researchers responsible for a study published in the latest issue of the scientific journal Science .
This group of researchers studied tissue from the nasal lining of 24 patients with covid-19, including nine who lost their sense of smell for at least four months. Tissue from patients with a loss of smell revealed that T lymphocytes involved in inflammation had infiltrated the nasal lining, where olfactory nerve cells can be found. This unusual immune response was observed even though the virus that causes Covid-19 was no longer detectable, suggesting that this response persisted even after the infection had cleared.
Bradley Goldstein, an associate professor of neurobiology at Duke University in North Carolina (USA) and one of the authors of the study, told The Guardian newspaper that the tissue lining the nose of these patients “contained unique immune cells that produce inflammatory signals, combined with fewer olfactory nerve cells.” The unusual response was seen only in patients whose loss of smell lasted for several months.
According to a study published in July of this year in The BMJ , about 5% of adults infected with covid-19 experience changes in smell and taste months after the illness.
The work estimates that, among the more than 550 million cases of infection already registered so far, at least 27 million adults may still suffer from deficiencies in smell or taste (15 million and 12 million, respectively). It concludes, therefore, that a “substantial proportion” of patients with covid-19 can develop lasting changes in smell or taste, which contributes to the “increasing weight” of prolonged covid-19 (“ long covid ”).
For now, there is no treatment for patients who experience prolonged loss of smell after being infected with the SARS-CoV-2 coronavirus, which causes covid-19. “To develop treatments, we need to understand the problem: what is damaged and where”, says Goldstein. But the findings of this study could pave the way for new treatments. Still according to the researcher, one option is to locally block the immune cells that lead to inflammation in the nasal lining, a part of the body that is easy to treat with creams and nasal sprays .