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Toronto, Ontario (CTV network) — Scientists are working to identify the cause behind loss of smell, one of the most characteristic side effects of early strains of COVID-19.
The symptom has become less common as new variants spread, but if you suddenly lost your sense of smell in 2020, it was an immediate sign to get tested for COVID-19.
And while this loss of smell is temporary for many, for others the sense is never properly restored, and millions of people suffer from the loss of smell for months and years. To find the mechanisms behind this, a new study examined olfactory epithelial samples collected from 24 people, including 9 people with long-term loss of smell due to COVID-19 cases. I was.
“One of the first symptoms usually associated with COVID-19 infection is the loss of the sense of smell,” said senior author of the new study, associate professor in the Department of Head and Neck Surgery and Communication Sciences and Neurobiology at Duke University. says Bradley Goldstein. , said in a press release.
“Fortunately, many people with altered sense of smell during the acute phase of viral infection regain their sense of smell within the next week or two, but some do not. We need a better understanding of what persists.We see persistent odor loss for months to years after being infected with SARS-CoV2.”
according to published research Earlier this year, as many as 5% of COVID-19 survivors suffered long-term loss of smell, an estimated 15 million people. About 17% of people lost their sense of smell when the Omicron subspecies became dominant in 2021.
In this recent study, researchers found that among people suffering from chronic olfactory loss after COVID-19 infection, nasal tissue with olfactory nerve cells was inflamed and there were fewer olfactory sensory neurons within the nose. I discovered that Overall, compared to the control group, the researchers suspected inflammatory damage may be the cause.
In a paper published in the journal Science Translational Medicine In mid-December, researchers explained that SARS-CoV-2, the virus that causes COVID-19, was not detected in any of the subjects, but in subjects with chronic odor problems, an ongoing Inflammation persisted.
Researchers obtained additional samples from people who had suffered from chronic olfactory impairment for at least four months after being infected with COVID-19. At the time of sampling, he had no acute illness with COVID-19 and no previous medical intervention such as intubation.
One of the major problems was that in patients previously infected with COVID-19, parts of the immune system were out of balance. Her T cells in the olfactory samples were working longer and causing inflammation.
The job of T cells is to attack specific foreign particles to help the body fight the virus, but in these patients the virus was long gone.
“The findings are amazing,” says Goldstein. “It’s almost like a sort of autoimmune-like process in the nose.”
This is important research into the problem that remains for people who can’t smell anything, a condition called anosmia, and a distorted sense of smell that affects their ability to eat food without nausea. Parosmia is the term used to describe a condition in which a person’s sense of smell is dulled and many objects smell sour or have chemicals attached to them.
Previous research on this topic focused primarily on autopsies of patients who died after being infected with COVID-19, so as the researchers did in this new study, patients were asked about their odor experiences and I couldn’t have them take a smell test.
While this study answers some questions, much more needs to be done to truly pinpoint the reasons for the long-term loss of smell in COVID-19 patients. This study points out that there are still several possibilities for the cause of long-term damage: one is that early cell damage in acute disease may lead to stem cells within the olfactory region being responsible for olfactory perception; There is a possibility that it overwhelmed the ability to reconstruct new cells.
A theory that appears to be disproved by this new study is that the long-term loss of smell was caused by an ongoing infection for which the researchers had not found any symptoms.
There was a silver lining – researchers have observed that neurons attempt to self-repair even after long-term damage.
“By modulating the aberrant immune response and repair processes in these patients’ noses, we hope to at least partially restore the sense of smell,” Goldstein said.
His lab is currently working on this aspect of the problem. The researchers acknowledged that their current study is limited by its narrow scope.
