Monitoring loss of smell could be key to COVID-19 detection

Researchers have found that persons who test positive for COVID-19 disease have common symptoms, including fever, cough, shortness of breath, and a temporary loss of the sense of smell. A commonly asked question is the difference between loss of sense of smell associated with common cold versus COVID-19. Researchers assure that the latter shows a more significant loss of smell. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) on their websites list fever, cough, and shortness of breath as the main symptoms of COVID-19 and recently have added two new symptoms –  the loss of sense of smell and taste.

Can smell be the determining factor in diagnosis?

With the novel coronavirus or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 1,911,407 individuals worldwide are reported as infected, and the death toll now stands at 118,854. Researchers explain that these numbers are the confirmed cases, and there may be many more persons who have the virus, either untested or are asymptomatic.

In some like France, patients who complain of sudden onset of loss of smell are being suspected to be positive for COVID-19 even without testing. In the United Kingdom, the Weizmann Institute of Science investigators, working with Edith Wolfson Medical Center, Israel, have developed an online platform called the SmellTracker. This tracker can effectively monitor a person’s sense of smell and detect COVID-19 early even before the other symptoms appear.

The tracker

Prof. Noam Sobel, from the Weizmann Institute’s Department of Neurobiology, works with the olfactory functions and feels that each individual had a unique sense of smell, and this may be an “olfactory fingerprint.” He and his team developed a mathematical model that can that characterize the sense of smell in an individual.

The olfactory fingerprint of the person in the middle remains consistent, even after 30 days (right), but is very different from that of another person (left)
The olfactory fingerprint of the person in the middle remains consistent, even after 30 days (right), but is very different from that of another person (left)

The team developed an algorithm that is used in an online test. It can help the user to map their sense of smell. For each of the tests, the sensor can help the user work through five different scents found in the home. These scents include spices, toothpaste, vinegar, extracts of scented substances and peanut butter. The sensor itself is a tiny wearable device weighing only six grams. It transmits data via Bluetooth.

Within five minutes, the test can monitor if there is any alteration in the sense of smell in the user. This could be an early indicator of COVID-19, the researchers explain.

How good is the app at detecting cases of COVID-19?

The researchers explain that this new sensor can successfully identify early and asymptomatic cases of COVID-19. Suspected cases are later confirmed to be positive for the coronavirus using standard tests, they wrote. Using the sensor, they explain, a unique olfactory fingerprint could be identified, and if there is an alteration, it could indicate the early stages of COVID-19.

What do we know of smell loss in COVID-19?

The first cases of COVID-19 were detected in Wuhan, Hubei province of China. In the patients infected with the novel coronavirus in the region, there were no reports of loss of smell, write the researchers. With time more and more cases were reported from other nations, including Iran and Israel. In around 60 percent of the patients with COVID-19, there was a significant loss of smell. Researchers in South Korea state that 30 percent of the patients test positive for loss of sense of smell in COVID-19 patients. Germany, too, has reported that two-thirds of their COVID-19 patients develop a loss of sense of smell or anosmia. This was announced by Claire Hopkins of the British Rhinological Society and Nirmal Kumar, president of ENT UK.

The researchers at Sobel’s lab explain that there are eight active strains of the coronavirus infecting people around the world. Sobel and his colleagues explain that the difference between the strains could lie in their ability to alter the sense of smell. Prof. Sobel said that the loss of sense of smell is quite rapid “with no restriction on nasal airflow.” He said, “That is, they can sniff, they’re not blocked. They don’t have a stuffy nose. But they just cannot smell a thing.”

Way forward

If the current research holds true, Sobel and colleagues believe that the SmellTracker app could help researchers map the outbreaks of COVID-19 across the world cost-effectively and straightforwardly.

The team is also developing simple kits called “scratch and smell” that can be sent to patients who have been confirmed to have COVID-19. The test would provide a detailed look at the duration of the alteration of olfactory senses in the coronavirus-infected patients. Unique questionnaires would also be given to the patients.

Israel’s Ministry of Defense is supporting this new venture, and soon it may be promoted in other regions, including Sweden and France. At present, the wearable sensor containing the smell test is available in English, Arabic, and Hebrew. It will soon be available in other languages, including French, Swedish, German, Persian, Spanish, and Japanese.

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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