Loss of smell isn't just a Coronavirus symptom. It could be key to slowing the spread.
Quarantine life is already enough fun when you still have a sense of smell. I realized mine was gone about a week and a half ago. I’d already had two solid days of what I assumed to be (mild) symptoms of COVID-19, the disease caused by the novel coronavirus: head and body aches, fatigue, a slight fever. The night between, I had some serious chills.
Overall, I was relatively lucky—though I don’t know for sure that I had it, since it is at this point unethical for me to seek a test that could go to better use. But it was only after the flu-like symptoms abated that I realized I was unable to smell food. Actually, a lot of the taste was stripped out of things as well. Because why shouldn’t one of the few remaining pleasures afforded to those of us blessed to live in the Year of Our Lord 2020—eating on the couch—get scratched off, too, along with "going places" and "doing things"?
To be clear, this wasn’t a zero-smell situation. There wasn’t nothing, some total absence of sensory input. There was something there that would flare up every time an external scent came wafting in. I would describe it as the scent of synthetic death, like some sort of chemical fire burned through the back of my nasal cavity and left a desiccated forest of nerve endings behind. When some odor would come billowing in, it would only succeed in activating the burnt-out nerves, like wind kicking up ash. Occasionally, the actual smell would poke through the smoke with around five or ten percent of its normal intensity. But the overwhelming sense was the back of my nose had become the California foothills during fire season.
Talking to some other folks here in New York—now d.b.a. The Epicenter—I personally know at least three people who believe they had COVID-19 and lost their sense of smell in the bargain. In fact, it's emerging as a fairly common symptom. To find out how common, and what the hell is happening here, I called up Claire Hopkins, a professor of Rhinology at King's College London and a consultant ear, nose and throat surgeon. As president of the British Rhinological Society, Hopkins released a statement last month on the organization's behalf tracing the growing evidence that anosmia is a symptom of the disease at the center of this worldwide pandemic.
"We often see post-viral anosmia," Hopkins told me, explaining they usually see it in patients who have the common cold and, because their noses are blocked up and stuffy, have lost some of their smelling capabilities. "But early on in the pandemic, I saw four patients in a row who were all young and healthy, who had, really in the absence of any other symptoms, lost their sense of smell. At the same time, I'd been participating in doctors' forums online, and colleagues from Italy had noticed that, amongst the doctors on the frontline, there were high numbers who had lost their sense of smell, and they speculated that this may be a sign of otherwise asymptomatic infection."
Around that point, Hopkins had a choice to make that became a question of medical ethics. On one hand, there was not much peer-reviewed evidence—the kind that scientists and doctors normally base their decisions on—of the link between COVID-19 and anosmia. In ordinary times, it would be unethical for the British Rhinological Society to make a statement on the possible connection.
But these were not ordinary times, and she began to worry that her colleagues in the field were at risk—particularly dangerous risk, because being an ear, nose, and throat doctor means getting up in people's faces, using tools that often cause patients to cough or sneeze—of contracting the virus from otherwise asymptomatic patients. (Regardless of what the governor of Georgia says, we have known for some time that asymptomatic spreaders pose a particular danger.) At the time, Hopkins was only using personal protective equipment (PPE) when seeing patients with respiratory distress, cough, or fever, and presumably so were most her colleagues in the field. Reports began to indicate there were high rates of COVID-19 infection in ENT doctors. Because part of her mandate is to look out for her colleagues' safety, she decided to go public using what she believed to be strong anecdotal evidence.
"I thought if we could include loss of sense of smell as one of the triggers to self-isolate," Hopkins says, "we might really reduce the risk of onward transmission."
Since then, researchers at Kings College London have developed an app, called the COVID-19 Symptom Tracker, for British citizens to document their Coronavirus Experience. It now has around 2 million users, Hopkins says, as Britons are encouraged to map their symptoms on a daily basis, even if they're feeling well. The goal is to learn more about the onset of the infection and "identify which symptoms occur at which stage of the disease." When Hopkins first put out the organization's statement, loss of smell was not included among the app's options. But she got in contact with the development team and convinced them to add it.
The app team released a statement this week announcing that sense of smell is "actually the strongest symptom to predict infection," according to Hopkins, including when compared to fever. They found 60 percent of patients who tested positive had lost their sense of smell, while in those that tested negative, only 18 percent had anosmia symptoms. This offers more specificity than a fever, which was commonly found in those who tested negatively. The takeaway, Hopkins says, was that "anyone with new onset loss of sense of smell should be self-isolating, and ideally tested." It's an early warning sign. Hopkins has developed a cohort of around 2,500 patients she's monitoring, and while the exact timeline of when anosmia occurs still isn't clear, she says around one-in-four lost their sense of smell before developing any other symptoms. Another one-in-four develop it around the same time as other symptoms, and for the other half, it comes after.
I was also interested in the mechanics here. Why does this happen—and in particular, why do I get the smell of synthetic death rather than nothing at all? Hopkins said the majority of patients report really severe loss. When they try to smell something, they get nada. A friend of mine told me this was his experience—he would try to smell coffee or candles and simply smell nothing. ("Onions," he said, "broke through the defenses.") But Hopkins says others have described "dysosmia"—when you go to smell something and it smells like something...else. Something unpleasant.
"We think there are problems with the receptors, so that pattern recognition is disrupted," Hopkins says. "But also, there are other nerves in the nose. For example, there's the trigeminal nerve, which detects noxious fumes, so it triggers a pain response. It also picks up thermal regulation. But it can pick up chemical smells. So when you smell menthol or cleaning fluids, it's actually stimulating the trigeminal nerve. When you take out our natural sense of smell, you still get some background stimulations through other pathways, that people often perceive as an unpleasant smell. So the loss of smell unmasks that background smell."
Apparently, this all has to do with how the virus takes root towards the back of the nose. "What we know is it's actually sort of an injury to the olfactory nerve, and the olfactory system itself," Hopkins says. Unlike with smell loss due to the common cold, there's no physical blockage in most COVID-19 patients. The odor is getting back there, but the receptors are damaged. "Coronavirus in particular can damage the nerve and then travel along the olfactory nerve to the olfactory bulb, which is the more simple processing part, and of course damage that as well," Hopkins adds. "Now fortunately, the olfactory nerves have the ability to recover, which is why they're being used in research for spinal cord injury. So they can regenerate and your sense of smell can return."
That was a somewhat crucial question for me. Is it going to come back? So far I'd say there's been significant personal improvement, but there are still times when the synth-death comes creeping in. "There are certainly people who have persistent, severe anosmia after post-viral infections," Hopkins says. "We know you can get persistent loss. Coronaviruses are known to cause long-term loss. Obviously, it's too early to tell what proportion of patients with COVID-19 will have long-term loss, but if you look at studies with post-viral loss in general, at least two thirds will make a good recovery. But that means that as many as one in three may not fully get their sense of smell back. In our cohort, at least 60 percent of people were seeing improvement within two weeks, and I just sent out a follow-up again today to try and see people beyond that."
And then there's the loss-of-taste situation. For a while there, everything I was couch-eating was mostly relegated to a texture experience. I was always under the impression that taste and smell were inextricably linked, that the two senses draw on the same chemicals in food to transmit information to the brain. This isn't strictly true.
"What we actually taste is sweet, sour, salt, bitter," Hopkins says, "and actually what we describe as 'taste' or 'flavor' actually all comes from sense of smell. So when we eat, we breathe out through our nose, we smell our food, we describe that flavor. So when you lose your sense of smell, food tastes very plain. People will report that they've lost their sense of taste," she adds, but that's something of an illusion.
Unless it's not. "Actually, we've had some patients describe finding it difficult to differentiate between salty, sour, bitter, and also getting a strange metallic taste. So it suggests [the infection] might be affecting taste in itself, and that certainly needs further investigation. What that suggests is that there may be some other central nervous system effects of the virus. We've also seen people describing change in hearing, and there are other effects, such as headache, drowsiness, severe central nervous system problems, suggesting that the virus can have wide effects within the nervous system."
Lovely. Apart from the time I tried to go for a run the week after my worst symptoms and it felt like I'd been repeatedly roundhouse-kicked in the chest, this is some of the more alarming feedback I've received on my case. Of course, this is all trivial compared to what many who are infected will experience. But as far as smell specifically, it does seem that for most people, it will come back. Hopkins says there's no need to seek medical attention if you lose your smell during the pandemic. Assume you've got COVID and self-isolate. If you want to feel like you're doing something about it, you can try "smell training," where you repeatedly smell something to stimulate the nerve and encourage recovery. But otherwise, there's no specific treatment. You're mostly at the mercy of the fascinatingly complex systems that make up our bodies and how they interact with the world outside—including the deadly pathogens that have the capability to upend our lives.