Nearly 78% of people who lost their sense of taste or smell tested positive for COVID-19 antibodies, a new study found.
Of the people who tested positive for antibodies, nearly 40% didn’t have a cough or fever during their illness.
Losing these senses is now a “good indicator of COVID-19,” doctors say.
A lost sense of smell or taste could be a hallmark sign of COVID-19, possibly even without the presence of other common symptoms, like a cough or fever.
In a new study published in the journal PLOS Medicine, researchers surveyed 590 people who had experienced a loss of taste or smell in the previous month. Of that group, 567 were given COVID-19 tests and nearly 78% tested positive for antibodies to SARS-CoV-2, the novel coronavirus that causes COVID-19.
Of the people who tested positive for antibodies, nearly 40% didn’t have a cough or fever during their illness. However, the researchers did find that people who experienced just a loss of smell were nearly three times more likely to have SARS-CoV-2 antibodies than those who had just a loss of taste. Those who had a loss of smell and taste were four times more likely to have the antibodies.
Study co-author Rachel Batterham, Ph.D., a professor at the University College London, says she and her research team conducted their study in April and May, during the peak of the first wave of COVID-19 in the U.K. “At this time, loss of smell was not recognized as a symptom of COVID-19,” she explains. “However, I was aware of colleagues who had developed sudden onset loss of smell, so we were convinced that this was a key symptom.”
Early on, people could not be tested for COVID-19 unless they had a fever or a persistent new cough, she says, and her study participants “were generally fairly well, none were admitted to hospital. We were surprised when so many tested positive.”
Why does COVID-19 cause a lost sense of taste or smell?
Loss of smell, a.k.a. anosmia, doesn’t just happen with COVID-19. It can also be caused by allergies, the common cold, and other upper respiratory infections, says Richard Watkins, M.D., infectious disease physician and a professor of medicine at the Northeast Ohio Medical University.
A viral respiratory infection, like COVID-19, can cause inflammation and swelling in your nasal cavity and that, along with nasal congestion, can alter your sense of smell, says Rachel Kaye, M.D., assistant professor of laryngology-voice, airway, and swallowing disorders at Rutgers University.
The virus also replicates (i.e. spreads) in the nose and throat, where it could mess with your sense of smell and taste before impacting the rest of your body, Dr. Watkins says.
So, how common is a loss of taste and smell in COVID-19 patients?
There’s no clear answer. “I see it occasionally, but still infrequently in patients,” Dr. Watkins says.
Other studies have found that anywhere between 15% to 68% of patients with COVID-19 report having a loss of taste and smell. But the new study results indicate that “loss of smell or taste seems to be a very common symptom of COVID-19,” Dr. Batterham says.
Infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security agrees. “I do think most people don’t necessarily recognize it as a symptom of infection. They may just think it’s odd and not related,” he explains. “But it seems to be a good indicator of COVID-19.”
If you suddenly develop a loss of taste and smell, Dr. Kaye recommends calling your doctor about getting tested for COVID-19. While losing these senses does not automatically mean you contracted the novel coronavirus, she says “there is a significant chance” it could be due to COVID-19, especially in the absence of other symptoms.
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