Loss of taste and smell may be top indicators of COVID-19

Losing the ability to smell and taste may be some of the clearest signs that someone has COVID-19. That’s the finding of a new study. It was based on data from a COVID-19 smartphone app.

Between March 24 and April 21, nearly 2.5 million people in the United Kingdom used that app. So did another 170,000 people in the United States. Each fed in data on whether they felt well or had symptoms.

Some of those app users had been tested for the virus and reported their results. Those tests use what’s known as PCR to search for genetic evidence of SARS-CoV-2. That’s the virus that causes COVID-19. In all, 6,400 U.K. residents and 726 U.S. participants had tested positive for this coronavirus. Nearly two in every three individuals known to have the virus reported having lost their sense of taste and small. Only about one in five people who tested negative had diminished senses.

Not everyone with COVID-19 has all the same symptoms. Claire Steves and Tim Spector work in England at King’s College, London. They led a team that used data from the app to figure out which mix of symptoms best predicted who had COVID-19. Among people already diagnosed with coronavirus, loss of taste and smell, extreme fatigue, cough and loss of appetite proved the most predictive symptoms.

Based on these data, the researchers estimated how many of the untested app users were likely to be infected, too. More than 800,000 people said they were ill. About 140,000 of those ill people probably have COVID-19, the researchers now predict.

They researchers shared their findings May 11 in Nature Medicine.

The World Health Organization lists loss of taste and smell as a less common COVID-19 symptom. But the King’s College team say their new findings suggest those sensory losses should be added to the list of top symptoms used to screen people for the disease.