Tuesday, October 26, 2021

Covid-19 may cause loss of smell

After taking away the joys of hugs, handshakes and the comfort of human touch, the novel coronavirus is now raiding our sense of smell, writes Dr Noor Gill

Stop and smell the roses was how we asked our folks to take a break and enjoy the little joys of life in the pre-corona times. After taking away the joys of hugs, handshakes and the comfort of human touch, the novel coronavirus is now raiding our sense of smell. Depriving us of the smell of rajma-chawal and wet soil after the first rain. How dare it muster the courage to threaten the one thing that was going right for us. But like the feeling of having forgotten something at home and running back to get it (mostly the mask these days) does this loss of smell also stay on? 

What is Anosmia? 

Firstly, let’s answer what anosmia really is? Anosmia is defined as the absence of all olfactory function, which can be caused by a variety of causes, with upper respiratory tract infections being a frequent cause. 

Patients with Covid-19 can present a sudden onset of anosmia without any other symptoms. However, in some other patients, before the onset of anosmia, other mild symptoms related to Covid-19, such as dry cough might also present. 

There is increasing evidence of olfactory dysfunction with the coronavirus. As said before, it can occur alone or it can be accompanied by other symptoms of coronavirus. 

The pathogenic mechanism of olfactory dysfunction and its clinical characteristics in Covid-19 patients still remains unknown. 

What do the studies say? 

However there have been cross sectional studies and research that has been working to find answers for all our questions. And here is what they have for us, till now- 

The American Journal of Otolaryngology, under the NCBI, publishes “In Covid-19 patients, the main manifestations were fever and cough and characterised by lymphocytopenia (lymphocytopenia is a condition of having abnormally low lymphocyte count in the blood. Lymphocytes are a type of white blood cells that play an important role in the functioning of the immune system) and ground-glass opacity changes on chest computed tomography (Chest CT). Patients with severe infection can also develop neurological manifestations such as acute cerebrovascular diseases, skeletal muscle injury and impaired consciousness. Besides, some patients may present with upper respiratory symptoms such as pharyngodynia (pain in the throat), sore throat, nasal congestion, rhinorrhea (discharge from the nasal cavity) and olfaction alterations. 

Olfactory dysfunction, including anosmia and hyposmia, manifests itself particularly prominently among these symptoms in Covid-19 patients. However, the extent of potential olfactory dysfunction manifestation of Covid-19 has remained unclear.”

During the study, when samples from the pharynx and the nasal cavity were taken from both symptomatic and asymptomatic patients, the viral loads in the nasal cavity were higher than those in the pharynx. Hinting that the nasal cavity might be the first gateway for the initial infection. 

What is the viruses possible mode of action and is the damage permanent? 

In another study done by the scientists and researchers at Harvard Medical School, they said, “Temporary loss of smell or anosmia, is the main neurological symptom in Covid-19patients and it is also the most commonly reported indicators of Covid-19. Studies suggest that the involvement of the nervous system presenting as loss of smell/taste better predicts the disease than the other well-known symptoms.” 

This being said, the underlying mechanism for loss of smell in patients with coronavirus has not been entirely understood. 

The olfactory sensory neurons don’t express the gene that encodes for the ACE-2 receptor protein which the coronavirus uses to enter the human body. So how does it manage to affect the patient’s sense of smell? Dr Sandeep Robert Datta an associate professor of Neurobiology in the Blavatnik Institute at Harvard Medical School says- “our findings indicate that the novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of the supporting cells. This indirectly caused changes in the olfactory sensory neurons.” 

This is not bad news, because this means that it is unlikely for SARS-CoV-2 infections to cause permanent damage or persistent anosmia. 

Every day, we learn something new about the novel coronavirus. Anosmia/loss of smell is something one should look out for, but it is also something that will not stay, as concluded by the studies done, as off this writing. It is not entirely good news, but seeing the infamy horrors the virus has been spreading, not entirely bad news is still good news.

Dr Noor Gill
Dr Noor Gill, MBBS, deciphers the space between heartbeats, figuratively and literally. Powered by frequent long naps and caffeine, she believes that “knowledge without giving back to society is meaningless” and works to make caring cool again.

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