Loss of smell, taste may hint at possible COVID-19 infection

British scientists monitoring the symptoms of the novel coronavirus-caused respiratory disease COVID-19 say a loss of the sense of smell and an inability to taste food should be added to the list of well-known indicators of infection, which include a high temperature, sore throat, and persistent dry cough.

The scientists made the discovery after analyzing data collected through an app, called Covid Symptom Tracker, that they developed to help monitor the pandemic.

The researchers from King's College London said around 60 percent of people who were subsequently confirmed as having COVID-19 reported a loss of smell and taste among their symptoms.

The information was gleaned from interactions between 1.8 million users and the app between March 24 and March 31.

Of those, most reported no symptoms but around 400,000 reported having symptoms commonly associated with the disease. Of those with at least one symptom, 1,702 had been tested for COVID-19.Some 579 of them had a positive result and 1,123 had a negative result and did not have the disease.

The team looked at the information harvested from the app and developed a mathematical model that was able to conclude which symptoms in combination were the best at predicting who would subsequently test positive for the disease.

The total basket of symptoms included fever, persistent cough, fatigue, diarrhea, abdominal pain, loss of appetite, and loss of smell and taste.

"When combined with other symptoms, people with loss of smell and taste appear to be three times more likely to have contracted COVID-19 according to our data, and should therefore self-isolate for seven days to reduce the spread of the disease," Tim Spector, the King's College professor who led the study, told the Reuters news agency.

Spector's team believes around w13 percent of the app users would have a positive result for COVID-19 if they took the test.

However, the team cautioned that a loss of smell and taste can also be an indicator of other respiratory infections, such as a common cold, so not everyone with those symptoms will have COVID-19.

They said a high fever and persistent cough remain the most important indicators of an infection and the loss of smell and taste should only be noted if they are in combination with other symptoms.

So far, Public Health England and the World Health Organization have not added a loss of smell and taste to their lists of common symptoms of COVID-19 infection. They say more research is needed.

ITV News quoted Stephen Powis, the national medical director of NHS England, as saying: "The two commonest (symptoms) are by far cough and a fever and that is exactly why they are the two symptoms that we are asking people to self-isolate if they get those symptoms."