Since the first reports from Wuhan from China, Iran, and later Italy, we have learned that loss of smell was an important symptom of Covid-19 disease.
And now, after several months of reports, experts believe they have a model of how the new corona virus causes a loss of smell, based on reports in which Simon Jane, consultant ENT surgeon at University of London, and Jane Parker, associate professor, at the University of Reading .
According to Russia today, viral infection is one of the most common causes of loss of smell, such as colds or other upper respiratory infections.
Corona viruses that do not cause deadly diseases, such as “Covid-19”, SARS and MERS, are one of the causes of the common cold and are known to cause odor loss.
In most of these cases, the sense of smell returns when the symptoms become clear, because the loss of odor is simply the result of a stuffy nose, preventing the odor molecules from reaching the olfactory receptors in the nose. In some cases, the odor loss can last for months and years.
As for the new SARS-CoV-2 virus, the pattern of odor loss is different. Many people with “Covid-19” reported a sudden loss of their sense of smell and then a sudden and complete return to their normal sense of smell within a week or two.
Interestingly, many of these people said their noses were open, so the odor loss could not be attributed to stuffy nose. For others, the sense of smell was lost for a long time, and after several weeks they had no sense of smell.
Now, after performing a CT scan of the noses and sinuses of people with an odor loss due to “Covid-19”, we can see that the portion of the nose that smells, olfactory fissure, is blocked by swollen soft tissues and mucus – known as fissure syndrome. The rest of the nose and sinuses appear normal and the patient does not have a problem breathing through his nose.
We know that the corona virus infects the body by binding to ACE2 receptors on the surface of cells, which line the upper respiratory tract. Then a protein called TMPRSS2 helps the virus to invade the cell.
Once in the virus, it can reproduce, leading to an inflammatory response to the immune system. This is the starting point for the devastation and damage this virus causes once in the body.
Initially, experts thought the virus could infect and destroy olfactory neurons. These are the cells that transmit the signal from the odor molecule in the nose, to the region of the brain where these signals are interpreted as “smell.”
However, recent international cooperation has shown that the ACE2 proteins needed by the virus to invade cells, have not been found on olfactory neurons. But it was discovered in cells called “ventral neurons” that support olfactory neurons.
We expect these support cells to be affected by the virus, and the immune response will cause the area to swell but leave the olfactory neurons intact. When the immune system deals with the virus, the swelling recedes and the odor molecules have a clear pathway to their undamaged receptors, and the sense of smell returns to normal.
Why does the smell not return in some cases? The cause can be caused by what we know about inflammation in other systems, which is the body’s response to damage and results in the release of chemicals that destroy the affected tissues.
And when this inflammation is acute, other adjacent cells begin to be destroyed or destroyed because of this “damage”. We believe this is the second stage, in which olfactory neurons are destroyed.
The odor recovery is much slower because the olfactory neurons need time to regenerate, from the supply of stem cells within the lining of the nose.
The good news is that olfactory neurons can regenerate. It grows in almost all of us, all the time. We can harness this rejuvenation and direct it to “natural nose therapy”.
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