A More Delicious COVID Screener
This story is a part of Science Friday’s coverage on the novel coronavirus, the agent of the disease COVID-19. Listen to experts discuss the spread, outbreak response, and treatment.
One of the most bizarre symptoms of COVID-19—a nearly surefire way to know if you have been infected—is a loss of taste or smell. Estimates of how many people are impacted range wildly, with the highest estimates reaching 75 to 80% of COVID-19 survivors. There’s still a lot scientists don’t understand about why this happens and what part of the olfactory system or brain is actually responsible for this change.
Researchers at Ohio State University are trying to figure out more about how COVID-19 impacts taste and smell using a familiar and tasty item: hard candy. Study participants eat an uncolored piece of candy each day and describe the flavor. If a participant is suddenly unable to identify which fruit the candy is emulating … well, it’s time to take a COVID test.
Joining Ira to talk about this delicious research and learning more about how COVID-19 impacts our senses is Chris Simons, sensory scientist at Ohio State University in Columbus, Ohio.
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IRA FLATOW: This is Science Friday. I’m Ira Flatow. A bit later in the hour, our annual salute to the strange and silly in science. Yeah, it is time for the Ig Nobel Prizes. First up, though, we are all familiar with the symptoms of COVID infection, right? Most notably, a fever. But there is a symptom that’s become a hallmark of infection, almost a surefire way to know if you have COVID-19. And that is a loss of taste or smell.
Yeah, it’s estimated that this loss affects somewhere between 5% and 75% of people who get COVID. The thing is there are still a lot of unanswered questions about how this loss of senses works and why it happens. So researchers are turning to a different method of testing, using hard candy to see if people can tell one flavor from another. And if they can’t, well, it’s time to take a COVID test.
Joining me now is Dr. Chris Simons, sensory scientist at Ohio State University in Columbus. Welcome to Science Friday.
CHRIS SIMONS: Thanks so much, Ira. I’m really happy to be here.
IRA FLATOW: Nice to have you. So what kind of candy are we talking about here?
CHRIS SIMONS: So we’re talking sort of the traditional hard candy Jolly Rancher style. So we actually partnered with a small company in North Carolina who made these candies for us. And they’re a little bit unique in the sense that they all look alike. We remove the colors that are often used to sort of signify the flavor of the candy. So they’re all sort of this opaque clear sort of color and then flavored with traditional familiar flavors that people will experience, hopefully, often as they’re consuming candy in their everyday lives.
IRA FLATOW: So the trigger then that makes them realize that they have lost their sense of smell or taste, they’re unable to detect the flavor of the candy.
CHRIS SIMONS: Exactly. So there’s really two pieces that we’re interested in. So one is the ability to identify the flavor. So we do that by having them both smell it before they put it into the mouth, as well as actually putting it into their mouth and then identifying the flavor. But we’re also interested in the intensity that people perceive. Because it’s possible with COVID that you actually have a reduced sensitivity, but you’re still able to recognize the flavors. And so we want to be able to capture both of those elements.
IRA FLATOW: Ah, so you’re looking for both smell and taste.
CHRIS SIMONS: We are actually looking for taste as well. So when I say smell, we’re looking at what we call often retronasal smells. So that’s when we put it in your mouth. And we often do this with we call it the jelly bean test. So if you put a jelly bean in your mouth and you plug your nose you know pinch your nose, you can’t tell what flavor it is until you release it. And it’s, oh, that’s the strawberry flavor or the orange flavor.
So that’s all retronasal smell. So we refer it to the mouth. And that’s one of the problems is that oftentimes in our common everyday vernacular, we call that taste. But taste is really sweet, sour, salty, bitter, and umami. And those sensations are transferred to the brain via different nerves. And so it’s actually really important for us to be able to measure both of those elements because there’s some question whether or not it’s smell loss that’s associated with COVID, which we seem to have pretty good documentation, of or whether that may also include taste loss, which I believe there’s much less empirical evidence to support.
IRA FLATOW: How much taste loss do you have to have? Maybe people have a taste loss for some other reason. Is there a limit or a threshold you have to pass to say, that’s COVID?
CHRIS SIMONS: Yeah, so the way this test works, so we’ve entered into what we’re calling phase two. So it’s really a prospective study. So it’s a way of actually allowing people to monitor their smell and taste over time. And so people will evaluate a candy once a day. And essentially what’s unique about COVID is the loss of smell and taste, potentially taste, is sudden.
So it’s not a gradual decrease like you see with a cold. And it’s pretty significant. And so the idea is that as people are evaluating these candies over time, if the system, so if the way that they’re inputting the data identifies sort of the sudden drop in their perceived intensity of those flavors or they’re no longer able to recognize the flavors, it sends a flag and says, hey, you’ve had symptoms that are consistent with COVID. You should go get tested. So we use their own historical data as a way of monitoring.
IRA FLATOW: I’ve heard a lot of anecdotes from people who got COVID, where some people lost their ability to taste a little bit. Some people lost it completely. Some people say that things taste different for them than they used to. Are you seeing this range in your study?
CHRIS SIMONS: That’s what’s really great about this, the way that we’ve designed it, is that we can pick up what is called anosmia. And I would say there’s different levels of anosmia. So anosmia’s basically the loss of smell. So it can be complete loss of smell.
There’s another phenomenon that is associated with taste, which is called ageusia. But if we sort of talk about anosmia in general, that’s the loss of smell. So you can have a complete anosmia, or you can have anosmia where it’s reduced sensitivity.
So in that case, you may still be able to identify the aroma as being cherry, for instance. But it’s suddenly very weak. And so now as you’re rating the intensity, your scores drop from something like an eight or nine down to like a three or four. So that would be indicative of somebody who has anosmia.
Somebody could have complete anosmia, where there they smell nothing. And they’re unable to both identify it– it’s basically like putting in a marble in your mouth. And so you would have no idea what flavor it is. And it wouldn’t have any taste.
IRA FLATOW: Wow. Do we know why this happens in the brain, what’s going on in the brain because of COVID-19, where you’re losing those senses?
CHRIS SIMONS: Yeah. Well, there’s a couple of different hypotheses. So we think what’s going on in these acute losses, so within these sort of first two weeks of infection, is an infection of the COVID virus into the support cells in the nasal cavity that support our olfactory neurons. These are cells that secrete mucus and help those smell neurons sort of survive. Those become infected with COVID. And it looks like COVID, when it enters those cells, it actually either kills them or essentially makes them sick. So they’re no longer able to do their job.
And as a consequence, the smell neurons, or those smell nerves, are no longer able to do their job. So that mechanism has been pretty well worked out and actually worked out fairly early in the COVID crisis. The same mechanism hasn’t really been identified for taste nerves. And so that’s why there’s some question as to whether or not people are really losing their sense of taste because the receptors that seem to be involved in binding to the COVID and bringing it into the olfactory or the smell neurons don’t seem to be expressed in the taste cells.
So if there is taste loss, there may be some differences in how that’s being done. But this is also really different from what we’re seeing in these so-called long COVID cases, so people that have experienced COVID for more than three months. And so in these cases, it’s more likely that there’s actually damage to the olfactory neurons likely due to inflammation or the inflammatory consequences of having the COVID infection, still not entirely known what the mechanism for this long COVID smell loss is.
IRA FLATOW: So you really need a lot of research to go into this.
CHRIS SIMONS: Yeah, exactly. And this is what’s kind of nice about this tool is that we can start to measure. So as people are doing this candy test, if they get COVID, we can start to measure sort of the recovery in these acute cases. So it seems like it’s roughly about two to three weeks. In which case, people start to recover. And then long COVID, how long do people have to experience smell loss in long COVID before they start to recovery? And this is really a question that we don’t know yet.
IRA FLATOW: Here in the US, Thanksgiving kicked off our holiday food season. Do you think the holidays are a good time to realize you’ve lost your sense of taste? I’m thinking you’re sitting down at Aunt Martha’s table and suddenly you say, oh, I don’t want to be insulting, but I don’t taste.
CHRIS SIMONS: [LAUGHS] Yeah, Aunt Martha, your cake doesn’t taste as well as it did last year.
IRA FLATOW: Do you think that’s happening during the holidays?
CHRIS SIMONS: Yeah, I think so. I think especially these effects are pretty dramatic. So it just so happens that my own experience is I actually had COVID early, early on in March of 2020. And so was before we actually even knew that smell and taste loss was a cardinal symptom. And actually my entire family got it.
We were in Spain. And we came back right before the borders were closed and so forth. And it was quite interesting because we had very varied responses. So I had anosmia, but it wasn’t complete. My wife had complete anosmia, and she was a long hauler. And so she had loss of smell and taste for probably about nine months. She just started to get it back maybe about six months ago.
IRA FLATOW: Oh, I’m so sorry to hear that.
CHRIS SIMONS: Yeah. And it was sort of slow. And so it’s interesting studying this and then also seeing it in real time in my own family and with myself. And so I think as you said with Thanksgiving, I have no doubt that people as they’re sitting down at the table and the foods that they’re expecting to taste great, don’t.
And so that should be a signal to people that ooh, maybe I should be wearing a mask at Thanksgiving table or something like that, right? Because the effects that are seen with chemosensory loss seem to be much more telling than other symptoms, such as fever, such as aches and pains. And that’s why it’s a nice way of assessing people as well because it’s a better predictor of somebody who has been exposed and has potentially has a COVID, an active COVID infection.
IRA FLATOW: Could you see the candy that you’re using to test people, see it rolled out on a larger scale? And would people be benefiting by using the candy? Or could they use something else? I guess I’m asking, what could you do at home to give yourself a test?
CHRIS SIMONS: Yeah. So candy’s really a fantastic tool for this because it’s amenable to all age groups, kids through the elderly. It’s inexpensive to make. It’s easily deployable. It assesses both smell and taste. So it allows us to sort of assess both of those systems.
But realistically you can really use anything. You can use coffee. I didn’t have any other symptoms besides smell loss. I was training for a marathon. So I was still running. I had zero– zero– symptoms. I actually made a cocktail for myself. And I was like, oh, my gosh, this doesn’t taste the same as it usually does.
And being in the field that I am, I knew that viral infection was often a cause of smell loss. And so this was before a lot of that data came out. And so, yeah, cocktails, coffee, cinnamon rolls– you can even use the fragrances that you plug in or whatever in your house. Anything that allows you to assess your sense of smell can be used as a monitoring system.
IRA FLATOW: Well, Dr. Simons, thank you for those words of wisdom on how to test yourself because as we’re sitting down to eat all during this holiday season, I’m certainly thinking about it all the time, and I’m sure you are. So thank you for taking time to be with us today.
CHRIS SIMONS: It’s my pleasure. Thanks so much for having me.
IRA FLATOW: Dr. Chris Simmons is a sensory scientist at Ohio State University in Columbus, Ohio.