Loss of smell (anosmia) was a significant symptom of the disease. Coronaviruses that don’t cause deadly diseases, such as COVID-19, SARS, and MERS, are one of the causes of the common cold and have been known to cause smell loss. One of the most common causes of smell loss is a viral infection, such as the common cold, sinus, or other upper respiratory tract infections.
Watch: Loss of Smell Explained by Experts
The COVID-19 pandemic, also known as the coronavirus pandemic caused by severe acute respiratory syndrome coronavirus 2. Many people with COVID-19 reported a sudden loss of smell and a quick return to an ordinary sense of smell in a week or two.
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Interestingly, many of these people said their nose was bright, so smell loss cannot attribute to a blocked nose. For others, smell loss prolongs, and several weeks later, they still had no sense of smell. Any theory of anosmia in COVID-19 has to account for both of these patterns.
COVID-19 smell loss can indicate that the part of the nose that does the smelling, the olfactory cleft, is blocked with swollen soft tissue and mucus – known as a cleft syndrome. The rest of the nose and sinuses look healthy, and patients have no problem breathing through their nose. SARS-CoV-2 infects the body by attaching to ACE2 receptors on the surface of cells that line the upper respiratory tract.
A protein called TMPRSS2 then helps the virus invade the cell. Once inside the cell, the virus can replicate, triggering the immune system’s inflammatory response. the ACE2 proteins the virus needs to invade the cells not found on the olfactory neurons. But they were found on cells called “sustentacular cells,” which support the olfactory neurons. When the immune system has dealt with the virus, the swelling subsides, and the aroma molecules have a clear route to their undamaged receptors, and the sense of smell returns to normal.
Inflammation is the body’s response to damage and results in the release of chemicals that destroy the tissues involved. Olfactory neurons can regenerate. They’re regrowing in almost all of us, all of the time. We can harness that regeneration and guide it with “physiotherapy for the nose.”