This article is a part of a series by The Better India to share verified information about COVID-19 care. While several posts on various aspects of fighting COVID-19 are being circulated on social media and messaging services like WhatsApp, we urge you not to trust unverified content. To separate fact from fiction, we will be sharing the videos and content with doctors and experts and bring you their responses with scientific research-backed information.
One of the symptoms of COVID-19 include loss of smell. According to a European study, patients with mild cases of COVID-19 were much more likely to report losing their sense of smell than patients with moderate to critical cases. Almost all the patients got their sense of smell back within 6 months, the study said.
Loss of sense of smell may be indicative of higher risk of pneumonia for certain groups, Hindustan Times said in a report.
To ascertain whether loss of smell in COVID-19 patients could be an indication of developing pneumonia at a later stage, The Better India spoke to Dr Bharat Gopal Senior Consultant, Pulmonology, Fortis Hospital, Vasant Kunj.
1. What is the significance of loss of smell in COVID-19 patients?
Dr Gopal: Early in the COVID-19 pandemic, it was reported that many people infected with the COVID-19 virus were complaining of a loss of sense of smell, even without exhibiting any other symptoms.
A study by Pierron, D. et al. in 2020 observed that self-reported changes in smell or taste were a better marker of the spread of the infection than many other indicators. So this symptom was touted as almost a surrogate marker for the RT-PCR test.
2. How many patients experience loss of smell?
Dr Gopal: While few studies have looked into it, the number of patients who experience a loss of smell can vary from 18-40 per cent in various cases.
In one questionnaire-based study, 96 per cent of the participants had some degree of olfactory dysfunction [reduced or distorted ability to smell].
According to the Centers for Disease Control and Prevention (CDC), Loss of smell (anosmia) or taste (ageusia) has been commonly reported, in a third of patients in one study, especially among women and younger or middle-aged patients.
3. What triggers loss of smell in COVID-19 patients?
Dr Gopal: Although the mechanisms are not fully understood, a team of researchers led by neuroscientists at Harvard Medical School have identified the olfactory [relating to smell] cell types in the upper nasal cavity most vulnerable to infection by SARS-CoV-2.
Surprisingly, sensory neurons that detect and transmit the sense of smell to the brain are not among the vulnerable cell types.
4. After having lost sense of smell, when is it likely to return?
Dr Gopal: In one of the large studies published in the Journal of Internal Medicine, 95 per cent of patients regained their sense of smell within six months.
In our experience, what we have noticed is that COVID-19 infection is unlikely to cause permanent damage to the olfactory circuits and lead to persistent anosmia [inability or decreased ability to smell]. Patients over a period of time gradually recover their sense of smell.
5. Is there a correlation between contracting pneumonia and losing sense of smell?
Dr Gopal: No, there is no clear evidence that links the two. We need to be vigilant in all cases, irrespective of the loss of smell, as 15 per cent of the cases may fall under the moderate-severe category.
Do not, therefore, rely on the loss of smell or any other olfactory senses to get tested and treated.
6. Are there any symptoms to check if the COVID-19 infection has reached the lungs?
Dr Gopal: Clinical symptoms like persistent and worsening cough, chest pain, blood in sputum or reduction in oxygen saturation on pulse oximeter are clear indicators of progression of COVID-19 to the lungs.
Adding to this, Dr Vikas Maurya said in an earlier interview, “When you have a persistent high-grade fever, it means lungs are getting involved. At this stage, it is imperative to reach out to your physician to get your medicines checked, and dosage increased or changed if the need arises.”
7. What is smell training? Can one actively work on getting their sense of smell back?
Dr Gopal: Researchers are calling for people struggling to regain their sense of smell after contracting COVID-19 to undergo “smell training”. This is a process that involves sniffing different odours over a period of months to retrain the brain to recognise different smells.
One treatment that has been prescribed by some doctors is a course of steroids hence the researchers are trying to see if smell training is safer and faster.
Smell therapy is not new — some of the first evidence that it might be helpful emerged in a 2009 study published in Laryngoscope for other diseases. The exact biological mechanism by which smell therapy helps patients improve this sense isn’t totally understood right now but the goal of smell therapy is to stimulate the sense of smell and assist with recovery.
8. If one loses their sense of smell, should they be worried?
Dr Gopal: No, as I mentioned earlier, 95 per cent of the patients recover their sense of smell within six months. I would advise them to be patient and not panic.
(Edited by Yoshita Rao)