Coronavirus: Scientists Uncovr Why Some People Lose Their Sense Of Smell

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From the first reports coming out of Wuhan, Iran and later Italy, we knew that losing your sense of smell (anosmia) was a significant symptom of the disease. Now, after months of reports, both anecdotal and more rigorous clinical findings, we think we have a model for how this virus may 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. Those 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. In most of these cases, sense of smell returns when symptoms clear, as smell loss is simply the result of a blocked nose, which prevents aroma molecules reaching olfactory receptors in the nose. In some cases, smell loss can persist for months and years.

For the novel coronavirus (SARS-CoV-2), however, the pattern of smell loss is different. Many people with COVID-19 reported a sudden loss of sense of smell and then a sudden and full return to a normal sense of smell in a week or two.

Interestingly, many of these people said their nose was clear, so smell loss cannot be attributed to a blocked nose. For others, smell loss was prolonged 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.

This sudden return of a normal sense of smell suggests an obstructive smell loss in which the aroma molecules cannot reach the receptors in the nose (the same type of loss one gets with a clothes peg on the nose).

Now that we have CT scans of the noses and sinuses of people with COVID-19 smell loss, we can see 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 normal and patients have no problem breathing through their nose.

By Simon Gane, Jane Parker
06-19-2020
Source and complete article by: theconversation.com