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August 26, 2020

COVID-19 smell loss: the story so far

An update from the President of the British Rhinological Society

Claire Hopkins.jpg

More than 325,000 people in the UK are thought to have had COVID-19, with smell and taste loss being one of the primary symptoms. Since May 2020, anyone experiencing sudden loss of smell and taste is advised to self-isolate and seek a test. According to Professor Claire Hopkins, President of the British Rhinological Society and leading advocate of the link with loss of smell to COVID-19, it’s a more reliable symptom than fever and high temperature. From a study in Belgium, 98 percent of people with sudden loss of smell and taste tested positive for COVID-19.

Although there are six million recovered cases reported worldwide, with less than 12 months data to work with, everyday brings new insights for the global network of scientists working on this issue. Organisations like the Global Consortium for Chemosensory Research (GCCR) - a group of 600 scientists, clinicians, and patient advocates across 50 countries founded in response to the COVID-19 pandemic - are coordinating surveys and sharing data to combat the spread of COVID-19.

The story so far

COVID-19 patients with anosmia - the loss of the sense of smell - seem to be falling into two distinct groups. The first group, or around 50 percent of those affected, recover smell and taste within about two weeks. Professor Hopkins suggests the nose lining is affected by swelling but recovers quite quickly because the cells do not die off. 

The second group experiences more persistent anosmia due to injury to olfactory nerves. Recovery in these cases can take four months and more. These patients with persistent anosmia also report intense and unpleasant bouts of parosmia - abnormality in the sense of smell. Food and familiar fragrances smell downright disgusting and this can cause real distress and feelings of depression.

Although parosmia seems to be a particular problem in COVID-19, it’s not uncommon. Where anosmia is a result of a virus other than coronavirus, 56 percent of people experience parosmia and it’s shown to be a good sign for recovery. Functional MRI scans show activation in unusual areas of the brain as olfactory nerves recover.

Professor Hopkins shared the theory that anosmia protects from more severe infection. Some olfactory nerves are programmed to die off which can prevent the infection from travelling any further into the central nervous system where it can cause significantly more damage. Olfactory nerves do regenerate, and the good news is that they are very likely to recover. 

According to the professor, “Time, support and smell training are the most important things you can be doing”.

Watch the complete presentation on YouTube https://www.youtube.com/watch?v=sd9wAxawtIU&t=23s