IN EARLY MARCH, Peter Quagge began experiencing COVID-19 symptoms, such as chills and a low-grade fever. As he cut pieces of raw chicken to cook for dinner one night, he noticed he couldn’t smell the meat. “Must be really fresh,” he remembers thinking. But the next morning he couldn’t smell the Dial soap in the shower or the bleach he used to clean the house. “It sounds crazy, but I thought the bleach had gone bad,” he says. When Quagge stuck his head into the bottle and took a long whiff, the bleach burned his eyes and nose, but he couldn’t smell a thing.

The inability to smell, or anosmia, has emerged as a common symptom of COVID-19. Quagge was diagnosed with COVID- 19, though he was not tested, since tests were not widely available at the time. He sought anosmia treatment with

multiple specialists and still has not fully recovered his sense of smell.

Case reports suggest that anywhere between 34 and 98 percent of hospitalized patients with COVID-19 will experience anosmia. One study found that COVID-19 patients are 27 times more likely than others to lose their sense of smell, making anosmia a better predictor of the illness than fever.

For most COVID-19 patients who suffer anosmia, the sense returns within a few weeks, and doctors don’t yet know if the virus causes long-term smell loss. While not being able to smell may sound like a small side effect, the results can be devastating. The sense is intricately tied up in self-preservation—the ability to smell fire, chemical leaks, or spoiled food—and in our ability to pick up on complex tastes and enjoy food.

“So many of the ways we connect with each other is over meals or over drinks,” says Steven Munger, director of the Center for Smell and Taste at the University of Florida. “If you can’t fully participate in that, it creates a sort of social gap.”

Smell even plays a role in our emotional lives, connecting us to loved ones and memories. People without smell often report feeling isolated and depressed and losing their enjoyment in intimacy. Now scientists are starting to unravel how COVID-19 affects this critical sense, hoping those discoveries will help thousands of newly anosmic people looking for answers.

The olfactory system, which allows humans and other animals to smell, is essentially a way of decoding chemical information. When someone takes a big sniff, molecules travel up the nose to the olfactory epithelium, a small piece of tissue at the back of the nasal cavity. Those molecules bind to olfactory sensory neurons, which then send a signal by way of an axon, a long tail that threads through the skull and delivers that message to the brain, which registers the molecules as, say, coffee, leather, or rotting lettuce.

Scientists still don’t fully understand this system, including exactly what happens when it stops working. And most people don't realize how common smell loss really is, Munger says. “That lack of public understanding means there’s less attention to try to understand the basic functions of the system.”

People can lose their sense of smell after suffering a viral infection, like influenza or the common cold, or after a traumatic brain injury. Some are born without any sense of smell at all or lose it because of cancer treatments or diseases like Parkinson’s and Alzheimer’s. It may also fade as people age. While smell disorders aren’t as apparent as hearing loss or vision impairment, data from the National Institutes of Health (NIH) show that nearly 25 percent of Americans over the age of 40 report some kind of change in their sense of smell, and over 13 million people have a measurable disorder like anosmia, the total loss of smell, or hyposmia, a partial loss. Such conditions can last for years or even be permanent.

It’s not clear if COVID-19 anosmia is different from other instances of smell loss caused by a virus, but those who experience anosmia due to COVID-19 appear to be unique in a few ways. First, they notice the loss of the sense immediately because it’s not accompanied by the congestion or stuffiness that generally characterizes the early stages of virally induced anosmia.

“It’s very dramatic,” says Danielle Reed, associate director of the Monell Chemical Senses Center in Philadelphia, which studies smell and taste loss. “People just cannot smell anything.”

Another notable difference is that many patients with COVID-19 who report losing their sense of smell get it back relatively quickly, in just a few weeks, unlike most people who experience anosmia from other viruses, which can last months or years.

Quagge estimates he’s recovered about 60 percent of his sense of smell so far, but he says in the early days, without any information about when or if he’d ever get it back, he was scared. An avid amateur chef, he had to rely on his family to tell him if the milk was bad, and he couldn’t smell his wife’s perfume. “Stuff that gets to your soul,” he says. “It bummed me out.”

(Adapted from https://www.nationalgeographic.com/science/2020/08/thousands-covid-19-patients-lost-sense-smell-will-get-back-cvd/)

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