Online smell-test can help detect COVID-19 cases and map their spread

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(Disponível em Português)

The test, called SmellTracker, offers an easy way to assess olfactory function and is available in 15 languages. Preliminary results indicate that this test may help individuals monitor their health as well as serve to detect and track the spread of COVID-19 across the population

The words cinnamon, honey, and coffee may bring to mind a lovely breakfast, but SmellTracker has an original use for these and other everyday household items – COVID-19 tracking. “By visiting the SmellTracker website and taking this simple test, anyone can easily assess whether their sense of smell is altered – an indication that they might have COVID-19”, says Zachary Mainen of the Champalimaud Centre for the Unknown, whose group is coordinating the SmellTracker study in Portugal. 

The loss of sense of smell has emerged as one of the main symptoms of COVID-19. Some experience it as an early symptom, followed by others, such as cough and fever, while for some it is the only physical sign of infection.

Though the loss of smell can happen due to other conditions, various studies and reports indicate that a sudden alteration in olfactory function appears to be a distinguishing feature of COVID-19. As it turns out, this unusual symptom, which in the majority of cases passes within a few weeks, may be a blessing in disguise.  

“The high infection rate of the virus means that finding a quick and easy way to detect COVID-19 cases is critically important, for personal and public health. However, widespread physiological COVID-19 testing is challenging to implement”, says Cindy Poo, a researcher involved in the study. “This is where SmellTracker comes in.” 

SmellTracker addresses this problem by allowing individuals to monitor their symptoms while gathering vital information about patterns of COVID-19 symptoms across the population. The test, originally developed in the lab of Israeli scientist Noam Sobel, collects subjects’ impressions about the pleasantness and strength of five odours (chosen by participants from a long list of options). At the end of the short test, the subject learns whether he or she is exhibiting an abnormal response. The test can be revisited freely, for continuous monitoring.

Is SmellTracker an effective way to track and monitor COVID-19? A study conducted in Sweden with thousands of participants has provided promising results. It showed that data collected with this test can predict population incidence of COVID-19 as well as other (non-olfactory) COVID-19 symptoms.

“This is a unique type of a citizen science project”, points out Poo. “At the individual level, this can help people make more informed decisions about their own health, such as seeking medical assistance sooner. Tracking these symptoms across many people may also help health authorities to monitor the spread of the disease more accurately and respond more quickly to an outbreak.”

Indeed, studies of this kind may have a far-reaching impact on public health policy. For instance, in the UK, studies like this one have led to the revision of general guidelines: now individuals who experience a sudden onset of this symptom are instructed to self-isolate, even if they are not exhibiting others.

As with most citizen science projects, one of the strengths of the project is its scale. To date, it has been running in nine different countries, and the number of participants is increasing daily. “We encourage people to visit the SmellTracker website and take the test. It is easy and actually interesting to assess one’s olfactory acuteness. The more people participate, the more we’ll know about the efficacy of this approach for personal and public health. And please remember that you should always consult a doctor if you think you have any symptoms of COVID-19, including loss of smell”, Mainen concludes. 

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