>>43589

I've seen multiple explanations and looks like there still no consensus about mechanism of smell loss. At least two main reasons are proposed: problem in nasal nerve cells and problems in brain nerve cells.

One main reason of uncertainty is evidence about long-term loss of smell - months and more. Nerve cells in nose must be restored faster, but this doesn't happen.

I've personally know person who was sick in January and still has no sense of smell, but there were no other serious symptoms, even almost no cough - everything was just like prolonged common cold. So, it is not related to severity of covid too, at least not directly.

I've experienced near two weeks of smell loss and all senses returned to normal. It is hard to compare though, because I never care about smells much in past and could be wrong.

This explanation >>43590 looks pretty good too.

>But to take away the sensing ability is new.

Smell loss can happen in different non-covid cases. For example, temporary loss is common for respiratory diseases, although it is rarely noticed, and may be partial (transport mechanism is damaged). Full smell loss is also happens, but mostly when people have brain-related problems (sensing mechanism is damaged). Covid case is interesting because it works more like brain-related, disabling smell completely and fast, but rarely does other brain damage at all.

One explanation of mechanism says that some covid proteins have affinity or look similiar as these nerve cells, and immune system attacks them heavily. Same mechanism explains inflammation and heavy pneumonia (parts of virus looks same as lung cells, so immune system kills both).