Loss of smell and taste are a strong sign that someone is infected with the coronavirus that causes Covid-19 -- and in some cases it may occur without the other symptoms of cough or fever, according to new research published Thursday. … Among those 567 people who were tested, 77.6% tested positive for Covid-19 antibodies. In total, 80.4% of participants reporting smell loss and 77.8% of those reporting taste loss had a positive test result, the researchers reported in the journal PLOS Medicine.