Published on Jul 15, 2020

  • The novel coronavirus can damage nerve cells responsible for sending smell and taste signals to the brain.
  • COVID patients are 27 times more likely than others to lose their sense of smell, according to a new study.
  • Results from the study suggest that temperature may not be the best way to gauge if someone is sick with COVID.

Video Transcript


JOHN WHYTE: Hi, everyone. You're watching Coronavirus in Context. I'm Dr. John Whyte, chief medical officer at WebMD. Have you had your temperature checked lately as you've entered a building or gone into a restaurant? They're pretty common right now. But are they the right test in trying to detect asymptomatic COVID-19? To answer that question, I've asked Dr. Andrew Badley. He's professor of medicine at Mayo Clinic. Dr. Badley, thanks for joining me.

ANDREW BADLEY: Good morning.

JOHN WHYTE: I was fascinated by your recent study that talked about-- you said that COVID-19 patients were 27 times more likely than others to have lost their sense of smell. But they were only 2.6 times more likely to have fever or chills. So are we measuring the right thing when we're looking at temperature as a detection method for asymptomatic COVID-19?

ANDREW BADLEY: Well, I think the results of our findings suggest that we should consider looking at other factors as well. We know that many patients who develop COVID infection or COVID disease do get fevers, but not all. And similarly, we know that a variety of patients who are COVID infected get a loss of a sense of smell and/or taste.

Now, why is that? We're not sure. But we can think of several possible reasons. So possible reason number one is that we know the virus can cause damage to neurons. And neurons are responsible for transmitting signals to and from the brain, including the signals of taste and smell.

The other reason that it's possible that-- that COVID may interfere with the sense of taste and smell has to do with a sodium transporter which is present, uh, in our airways and-- and nose and mouth. And it turns out the SARS-CoV-2 virus itself may interfere with that sodium transporter.

But going back to your original question, what should we screen for as we're looking for asymptomatic cases, certainly, if we had a person who was otherwise healthy, did not have preexisting reasons for loss of taste and/or smell, that should raise our index of suspicion that-- that they could have, uh, SARS-CoV-2 infection whether or not they had additional symptoms as well.

JOHN WHYTE: So what should patients be thinking about at home? Because we talk about loss of smell, loss of taste. You know, what's a good measure for them, um, you know, to understand that symptom? We can't just say they'll know it when-- when they know it.

Is it because that orange juice in the morning tastes a little funny or, you know, there's flowers in the house that they enjoy that, you know, they're not appreciating? What are some of the tools that viewers could use to say, you know what? Maybe I'm losing my sense of smell or my sense of taste. And I need to talk to my doctor.

ANDREW BADLEY: Yeah. So-- so great question. So there's a variety of tools that clinicians use to assess that. And when and if you see your physician, then they'll use those.

But at home, I think a good screen is to take things that are normally vibrant smells and taste for you. So that could be a freshly brewed pot of coffee, orange juice, flower, peppermint. And most people will have an understanding of what that normally smells like and tastes like. And if that is altered, that is a suggestion.

And-- and what you should do with that information is probably two things. One is talk to your health care professional. And the second is, until you have had that conversation with your health care professional, try to socially distance in case you are one of those asymptomatic cases so you don't spread it to others. Not everybody who has lost their taste-- sense of taste and smell is going to end up having SARS-CoV-2 infection. Um, but it is a good screening maneuver I'd suggest.

JOHN WHYTE: Is it often the only symptom? So if I didn't smell that, you know, fresh pot of coffee in the morning but I don't have any other symptoms, like cough, or I just feel lousy, is that a good predictor as a sole symptom? Or is it often in conjunction with others? Help us think through as consumers maybe watching this to think like, what should I do?

ANDREW BADLEY: So-- so that's a great question. Is it a good predictor in any context? We don't know that yet. We-- we know that it's associated. Is it a good predictor? Studies will have to tell. Some patients who-- whose data is included in our study did have that as the only finding. So it is possible. But is it a sensitive and/or specific screen? We don't have enough data to answer that yet.

JOHN WHYTE: You mentioned your doctor might do a more vigorous test for smell. I'm not so sure many of them will. I'm in-- in primary care, and I haven't done a smell test. They may just simply do a COVID test. But I saw the gold test is the University of Pennsylvania, my alma mater, smell identification test. But is that realistic in clinical settings as opposed to research settings-- that they use 40 different types of scents?

ANDREW BADLEY: Point well taken. Um, it is unlikely that you're non-smell specialist is going to do a full screen of 40 tests, no question about it. There-- there are physicians who can be in ear, nose, and throat or neurology or both who do specialize. And they'll do a much more detailed level of examination.

JOHN WHYTE: And what made you do research in this area? Was it just the anecdotes that you had been hearing from patients who had COVID who had consistently been talking about loss of smell or taste? How-- how did you come upon this discovery?

ANDREW BADLEY: So exactly right. In my research career, we have always tried to take what patients are telling us and convert that into testable hypotheses and find out if it's real or not. And that's true in the laboratory and in the clinical setting. And this research was initiated based on some of the anecdotes we were hearing from patients.

And so we use that to delve into patients' medical records to understand, how common is this symptom? And is it more common than other symptoms that would be more common when you think of as being associated with COVID disease.

JOHN WHYTE: What do you-- what do you see the future? Do you see us, um, smelling things to-- to get on a plane or as entry to school? You know, I'm being somewhat tongue in cheek. But your data are pretty robust in terms of detecting, you know, early COVID. Is that something that we should be thinking more about-- using a smell test? What's on the horizon, Dr. Badley?

ANDREW BADLEY: Yeah. So-- so my thought is that before we use it as a screen to get on an airplane or go in a restaurant or go to school, we have to study it more. And by that, I mean we need to do studies in patients who have as their symptoms loss of taste and/or smell and determine how often that's associated with SARS-CoV-2 infection. And results of that will inform how we should use it for screening purposes.

JOHN WHYTE: Well, Dr. Badley, I want to thank you for providing your insights today and helping us to understand the role of smell, the role of taste, uh, with COVID. And you've given us some good advice. If, you know, a consumer of yours is experiencing loss of smell or loss of taste, they definitely should be thinking about self-quarantining and talking to their physician and having additional testing. Is that right?

ANDREW BADLEY: I fully agree with that recommendation. And thank you for having me on your program today.

JOHN WHYTE: Absolutely. And thank you for watching Coronavirus in Context.