How Could Covid-19 Cause Someone To Lose Their Sense Of Smell?

How Could Covid-19 Cause Someone To Lose Their Sense Of Smell?

In early March, 27-year-old California resident Isabelle Rosa began to experience symptoms that she would have brushed off as a typical flu just a few months ago.

But as her fever and dry cough lingered, and as the growing threat of the novel coronavirus to the U.S. became impossible to ignore, Rosa suspected that she may indeed have covid-19. Alas, as many people in the U.S. have experienced, Rosa was told remotely by a doctor to stay home, without getting tested, so long as her symptoms didn’t turn serious.

While her symptoms didn’t become life-threatening, they did become stranger. About three days into her illness, Rosa suddenly realised that she could no longer smell or taste anything.

“I found out because I drank spoiled milk. I had no idea I couldn’t taste it. And then with smelling, I couldn’t smell anything like perfume. I ate a lemon—no reaction. I’ve pretty much smelled around 50 different things and probably tried tasting around 30. Nothing,” Rosa told Gizmodo. More than a week later, as of March 24, her senses of smell and taste remain impaired.

Rosa isn’t the only person with suspected or confirmed covid-19 to report a loss of smell or taste as one of their symptoms in recent weeks. As the epidemic has swept across the globe, so too have local news reports of people experiencing these conditions. But what exactly about the newly discovered disease could be causing it? And could these distinctive symptoms have greater implications for how we track the disease?

There are more than a few ways to end up without a sense of smell and/or taste, conditions respectively known as anosmia and ageusia (because our sense of smell so heavily affects our sense of taste, the two conditions are often co-diagnosed). You can be born with a congenital disorder. You can get a neurological condition or traumatic injury that severs the brain’s ability to process information from the cranial nerve located between the nose and brain, known as the olfactory bulb. Or you can get a viral infection. When that last method happens, it’s often chalked up to respiratory illnesses like covid-19. But contrary to what you might guess, anosmia is not likely caused by a congested nasal passage, nor is it usually a sign of serious brain damage, according to Canadian clinical neurologist Paul Masiowski.

“The understanding is that respiratory viruses can cause damage to the sensory receptors for olfaction, which are needed for a normal sense of smell. There may also be some swelling of the olfactory nerve, which can lead to it bruising or pinching itself off completely,” Masiowski, who is not an ear, nose, and throat specialist but has treated patients with anosmia, told Gizmodo. “It wouldn’t usually be painful. And people don’t necessarily have especially bad nasal congestion at the moment the nerve function is damaged. It’s common to temporarily have a decreased sense of smell when the nose is plugged, like with a cold. But that tends to resolve when the congestion clears up.”

While there have been scattered reports of covid-19-related anosmia in Germany, Iran, and now the U.S., people like Rosa have primarily taken to social media outlets and forums like Reddit to voice their frustrations. It’s only in recent days that public health experts have started to look into the connection. On Monday, World Health Organisation officials said they were beginning to study the link, while cautioning that any evidence for the connection was preliminary.

There are a lot of unknowns about the relationship between covid-19 and anosmia. One key question is whether people with the infection are more likely to develop anosmia than those who come down with the typical flu or cold bug. Another is whether this complication is more severe or permanent in covid-19 patients than in people who have other viral infections. Anecdotally, many Reddit commenters have said their anosmia remains even as they’ve stopped feeling sick, while others report they have started to return to normal.

“With this form of anosmia, people can have a significant decrease in their sense of smell—even losing it completely—and that can continue long after the nasal congestion has gone. Some of the anosmia may improve with time, but the fear is that a significant part of the damage may be permanent.”

Masiowski isn’t so sure that covid-19 is causing more anosmia than a cold virus might—rather, it could be the spike in cases and worldwide focus on covid-19 that’s driving people to notice and speak out about their symptoms. But he thinks that it could very well serve as a rudimentary beacon for the disease.

In his free time, Masiowski has taken to combing Google search trends for terms like “loss of smell” in the native language of countries affected by covid-19. So far, he’s found a consistent pattern where people in those countries are now searching for anosmia-related terms en masse, sometimes before it’s obvious an outbreak is widespread there.

While the best way to track covid-19’s path through the world would be extensive testing (preferably with blood tests that can find antibodies against the coronavirus, regardless if someone is currently sick) and genetic analysis of the virus’s evolutionary history, Masiowski believes this sort of method could be used in the meantime to roughly trace where and when the virus has hit. Though Masiowski has no immediate plans to pursue his theory, researchers already employ social media as a way to detect and predict the trajectory of flu seasons. If nothing else, anosmia could also be another warning sign of covid-19 that doctors actively screen for, a suggestion made recently by the American Academy of Otolaryngology.

The lack of initial attention paid to this symptom by public health experts seems to reflect the short shrift that people who develop anosmia get in general. While certainly not as dangerous as severe pneumonia, it can be a frightening and life-altering experience.

“It’s really troubling. I don’t think I honestly appreciated my senses as much as I should have—it’s emotional. I like to cook a lot, as something that makes me feel good, and now I can’t taste anything I cook,” Rosa said. “I do feel a little depressed, and I don’t think a lot of people would consider something like this to be something you suffer.”

Masiowski’s experience in treating anosmia has given him added sympathy for people like Rosa. While people with the condition can regain some or all of their ability to smell, even if it takes years, there’s often little he can do for the patients who visit him, the window of opportunity to treat a potential cause (such as a viral infection) having been shut. He hopes these stories can galvanize young or healthy people to do as much as they can to avoid getting sick in the first place.

“If you’re in your 20s or 30s and you lose your sense of smell this month to covid-19, and then you live for 50 or 60 more years, and everything sucks—every meal you have for the rest of your life is worse—that is a serious impact on your quality of life. But this is a disease that’s been framed around how harmless it is to young people,” he said. “So my hope on this would be to educate people on this potential risk to them.”