December 5, 2021

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Why do some people lose their sense of smell due to Covid-19?  Researchers find part of the reason |  Science

Why do some people lose their sense of smell due to Covid-19? Researchers find part of the reason | Science

Loss of smell is a common symptom of Covid-19 and is often the only symptom. More than 40 percent of Covid patients lose their sense of smell at least temporarily. At the moment, it’s not clear exactly how this happened, but an international research team that also includes UZ Leuven and AZ Sint-Jan Brugge-Oostende has discovered part of the reason. Their findings were published in Professional Cell Journal.




Loss of smell (loss of smell) has been one of the reported symptoms of Covid-19. The loss of smell is usually temporary, although about 5% of sufferers experience a reduced sense of smell for a longer period of time. This is often accompanied by a decreased sense of taste. How exactly this is and what exactly the virus does to our olfactory organs has long been a mystery, but new research is already shedding some light on the veil.

The good news is that the coronavirus does not affect the nerve cells of the olfactory organ. According to experts, the virus, via the olfactory nerve, is unlikely to damage brain tissue or cause permanent damage. In some cases, the virus was present in the meninges, but the cause and consequences of this are still unknown.

Bruises in the olfactory system

The virus infects the supporting cells or “bruising the olfactory system,” according to Laura van Gerven, MD, an otolaryngologist and ear doctor at the University of Leuven. Little is known about those support cells, which were thought to play a very small role in the olfactory organ. One of the lead researchers, Peter Mombaerts, explains that “infection of the support cells may indirectly cause abnormal functioning of the olfactory mucosa, and consequently a impaired sense of smell.” “What we do know for sure is that our bodies are constantly producing new support cells, which may explain the temporary nature of the loss of smell.”

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Anosmia is the complete loss of the sense of smell. Congenital defects are somewhat rare. Brain damage and sinusitis are the most common causes, but age-related diseases such as Parkinson’s disease and Alzheimer’s disease can also lead to a loss of smell.

Tissue samples from 70 deceased patients

In the cohort study, a study in which people were exposed to a risk factor (read: Covid-19 infection) for a period of time, tissue samples were taken through the noses of 70 deceased Covid-19 patients and 15 control patients.

The researchers used a technique that makes it possible to remove a very minute part of the mucous membrane of the respiratory tract, the olfactory mucosa, and the odor center in the brain. The sample is taken with the help of a small camera, or endoscope, so that the outside of the body remains completely intact. It is the first time that this technology has been used for research purposes.

“Due to the unique design of the study, the quality of our samples was very good: they were all usable for analysis, which is very exceptional in postmortem studies,” explains Van Gerven. As a result, we were able to catch the virus “red-handed” in them, while still a lot of new virus particles are produced in the olfactory mucosa.

The clinical study is now underway. Researchers want to learn more about the injury to the supporting cells and why some patients’ loss of smell does not fully recover.