Why do some COVID-19 patients lose ability to taste and smell? A team of Duke doctors is working to find out

DURHAM, N.C. (WTVD) -- A team of Duke doctors are teaming up to study one of the most common and longest-lasting symptoms of many COVID-19 patients: the loss of taste and smell.

"When it became clear that COVID-19 is causing fairly commonly persistent loss and taste disorders, it was sort of a natural collaboration with us to team up to try and tackle this problem," said Dr. Goldstein, an associate professor at Duke's School of Medicine in the Department of Head and Neck Surgery. The team began studying these issues in early spring.

"There are two things we should think - how to mitigate this short-term olfactory loss and how to make these long-term olfactory loss patients regain their sense of smell," said Dr. Hiroaki Matsunami, a neurobiology professor at Duke.

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Dr. Goldstein and Dr. Matsunami are joined by Dr. Nicholas Heaton, an assistant professor in the Department of Molecular Genetics and Microbiology, and Dr. Ashley Moseman, an assistant professor in the Department of Immunology.

A study published in the Journal of Internal Medicine looked at COVID-19 patients in 18 European hospitals, and found that nearly 86% of those with a mild case reported a loss of smell. While most patients regained their ability to do so within a few weeks, in some instances it takes several months.

Loss of smell is prevalent in other conditions, though it presents differently in COVID-19 patients.

"They can still breathe through the nose, no problem, yet they lose smell. And in previous knowledge, the virus mediated loss of smell usually associated with severe inflammation. Basically the clogged nose, stuffy nose, and then they can't smell it. But not this time," said Dr. Matsunami.

Researchers are working to learn how COVID-19 attacks those senses.

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"We wanted to focus on the mucus membrane because it is an accessible tissue in humans, and a likely site of pathology for coronavirus infections," said Matsunami in an earlier interview with Magnify, a magazine published by Duke's School of Medicine. "Not only that, it houses many types of cells, including olfactory sensory neurons, which have a direct line to the central nervous system. Healthy functioning of these neurons is necessary in order for a person to be able to smell."

"Probably about 15% of subjects seem to have this more long-lasting smell loss. And we don't really know why that is. And we've been seeing five, even six months out form COVID infection in my clinic complaining that their sense of smell is not returning. And we even give them smell tests that show their sense of smell is not functioning normally," said Dr. Goldstein.

They believe the loss of taste is tied to the loss of smell.

"As we're eating and chewing, all the volatile components of the food we're eating sort of go up behind your pallet and are actually detected by your smell nerves. So actually your brain is putting together input from your taste buds," said Dr. Brad Goldstein.

Dr. Goldstein explained there is some anecdotal evidence that smell therapies could help, though further studies are needed. Once they have a better understanding of how the virus attacks the senses, researchers hope to move to the next phase.

"Moving forward we would then anticipate hopefully starting some specific studies to test treatments," said Dr. Goldstein.
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