Loss of smell could be a ‘highly reliable indicator’ of Covid-19, research says

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.

The researchers, based in the United Kingdom, wrote in their study that people who lose either smell or taste should consider self-isolating, even if they have no other symptoms.

“Our findings show that loss of smell and taste is a highly reliable indicator that someone is likely to have Covid-19 and if we are to reduce the spread of this pandemic, it should now be considered by governments globally as a criterion for self-isolation, testing and contact tracing,” Rachel Batterham, of University College London and University College London Hospitals, who helped lead the study team, said in a news release on Thursday.

The team studied 590 volunteers who experienced a new loss of smell or taste, and they tested 567 of them for Covid-19.

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.

About 40% of those who tested positive for antibodies had neither a fever nor a cough.

Batterham and her colleagues also found that participants with loss of smell alone were nearly three times more likely than patients with just a loss of taste to have Covid-19 antibodies, and participants with a combined loss of smell and taste were four times more likely to have antibodies.

“These findings suggest that a loss of smell is a highly specific symptom of Covid-19, in contrast to a loss of taste, despite their comparable frequency,” the researchers wrote in the study.

The study recruited its volunteers between April 23 and May 14, during the peak of the Covid-19 outbreak in London. The findings come with some limitations, including that the study does not include a comparison group of people who did not lose their sense of smell and/or taste.

Overall, the loss of smell — called anosmia — emerged early on in the pandemic as a possible Covid-19 symptom. In May, it was added to the official list of coronavirus symptoms in the United Kingdom, the Department of Health and Social Care announced.

At the time, a government statement said that “all individuals should self-isolate if they develop a new continuous cough or fever or anosmia.”

CNN’s Jacqueline Howard contributed to this report.