BackLoss of smell a covid sign to watch out for
A study used symptoms of around 824,000 users of a mobile app to conclude that loss of smell and taste was quite prevalent among those who tested positive for coronavirus
PremiumLoss of smell, or anosmia, recently entered the World Health Organization’s list of possible symptoms of the coronavirus infection. Days before, a study in Nature had found that loss of smell and taste was a more common covid-19 symptom than believed, and thus, could help predict the infection.
Researcher Cristina Menni and others examined symptoms reported by users of a mobile app in the US and the UK. Though 2.6 million users reported having symptoms, only around 824,000 identified specific ones. Of these, 18,401 said they had got tested for covid-19, and 7,178 were found positive. The researchers found that around 65 percent of those who turned positive had reported loss of smell and taste, but this was only around 20 percent for those who tested negative.
The researchers used this to suggest that loss of smell and taste could be used to identify potential mild cases rather than just relying on flu-like symptoms. Impact on smell receptors has been observed even in other respiratory viruses and previous coronaviruses.
The authors said it is important to look at combinations of symptoms such as loss of smell along with fatigue, cough and loss of appetite. Using such combinations reported by positive cases on the app, they predicted that 17.4 percent of those who identified symptoms but did not get tested could also be infected. This means 5.4 percent of the app responders were likely to be infected as opposed to only 0.3 percent who actually tested positive.
While the model has limitations as it is based on self-reported symptoms and may have over-predicted infections, it provides emerging insight on the varying symptoms of a new disease. As of now, most countries rely on established flu symptoms for testing and isolation. A restrictive definition would mean non-detection of mild and asymptomatic cases. Looking for loss of smell as well could help detect more cases.
Also read: Real-time tracking of self-reported symptoms to predict potential COVID-19
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