A loss of smell and taste may be one of the clearest indicators of whether someone has COVID-19, a new study suggests.
Researchers gleaned the information from nearly 2.5 million people in the United Kingdom and about 170,000 people in the United States who entered whether they were feeling well or experiencing symptoms into a smartphone app from March 24 to April 21.
Some of the app users also reported results of PCR diagnostic tests for the SARS-CoV-2 virus, which causes COVID-19 (SN: 3/6/20). Nearly 65 percent of roughly 6,400 U.K. residents who tested positive for the virus described a loss of taste and smell as a symptom, researchers report May 11 in Nature Medicine. And just over 67 percent of the 726 U.S. participants with a positive test also reported losing those senses. Only about 20 percent of all people who tested negative had diminished smell and taste.
Using data from the app, a team of scientists led by clinical researchers Claire Steves and Tim Spector, both of King’s College London, devised a formula for determining which symptoms best predict COVID-19. A combination of loss of taste and smell, extreme fatigue, cough and loss of appetite was the best predictor of having a positive result from the PCR test, the team found. Based on those symptoms, the researchers estimate that more than 140,000 of the more than 800,000 app users who reported symptoms probably have COVID-19.
The World Health Organization lists loss of taste and smell as a less common COVID-19 symptom. But the new findings suggest that it should be added to the list of top symptoms used to screen people for the disease, the researchers say.