New York Times  2021.01.02

As the coronavirus claims more victims, a once-rare diagnosis is receiving new attention from scientists, who fear it may affect nutrition and mental health.

Until March, when everything started tasting like cardboard, Katherine Hansen had such a keen sense of smell that she could recreate almost any restaurant dish at home without the recipe, just by recalling the scents and flavors.

 

Then the coronavirus arrived. One of Ms. Hansen’s first symptoms was a loss of smell, and then of taste. Ms. Hansen still cannot taste food, and says she can’t even tolerate chewing it. Now she lives mostly on soups and shakes.

“I’m like someone who loses their eyesight as an adult,” said Ms. Hansen, a realtor who lives outside Seattle. “They know what something should look like. I know what it should taste like, but I can’t get there.”

 

A diminished sense of smell, called anosmia, has emerged as one of the telltale symptoms of Covid-19, the illness caused by the coronavirus. It is the first symptom for some patients, and sometimes the only one. Often accompanied by an inability to taste, anosmia occurs abruptly and dramatically in these patients, almost as if a switch had been flipped.

Most regain their senses of smell and taste after they recover, usually within weeks. But in a minority of patients like Ms. Hansen, the loss persists, and doctors cannot say when or if the senses will return.

Scientists know little about how the virus causes persistent anosmia or how to cure it. But cases are piling up as the coronavirus sweeps across the world, and some experts fear that the pandemic may leave huge numbers of people with a permanent loss of smell and taste. The prospect has set off an urgent scramble among researchers to learn more about why patients are losing these essential senses, and how to help them.

 

“Many people have been doing olfactory research for decades and getting little attention,” said Dr. Dolores Malaspina, professor of psychiatry, neuroscience, genetics and genomics at Icahn School of Medicine at Mount Sinai in New York. “Covid is just turning that field upside down.”

Smell is intimately tied to both taste and appetite, and anosmia often robs people of the pleasure of eating. But the sudden absence also may have a profound impact on mood and quality of life.

 

Studies have linked anosmia to social isolation and anhedonia, an inability to feel pleasure, as well as a strange sense of detachment and isolation. Memories and emotions are intricately tied to smell, and the olfactory system plays an important though largely unrecognized role in emotional well-being, said Dr. Sandeep Robert Datta, an associate professor of neurobiology at Harvard Medical School.

“You think of it as an aesthetic bonus sense,” Dr. Datta said. “But when someone is denied their sense of smell, it changes the way they perceive the environment and their place in the environment. People’s sense of well-being declines. It can be really jarring and disconcerting.”

 

Many sufferers describe the loss as extremely upsetting, even debilitating, all the more so because it is invisible to others.

“Smell is not something we pay a lot of attention to until it’s gone,” said Pamela Dalton, who studies smell’s link to cognition and emotion at the Monell Chemical Senses Center in Philadelphia. “Then people notice it, and it is pretty distressing. Nothing is quite the same.”

 

British scientists studied the experiences of 9,000 Covid-19 patients who joined a Facebook support group set up by the charity group AbScent between March 24 and September 30. Many members said they had not only lost pleasure in eating, but also in socializing. The loss had weakened their bonds with other people, affecting intimate relationships and leaving them feeling isolated, even detached from reality.

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