Lack of smell, a symptom of Covid-19

One day he woke up and was gone. "Disappeared," she whispers resignedly, bathed in the morning light. "My smell disappeared."

Days go by and, overwhelmed by thousands of cases similar to hers, Susan throws in the towel: “But life goes on. Food becomes spicier, saltier, sweeter, more bitter. You get used to it. The biggest loss is all the memories that are no longer triggered by a smell. Smell and memory are connected in the brain. The cinnamon might have reminded you of your grandmother's apron. Without smell, an ocean of past images disappears ”.

The testimony of this young epidemiologist sounds like that of several people whose bodies have been intimately altered by the coronavirus since the beginning of last year. The only difference is that Susan's (actually actress Eva Green) nose blew out in 2011. It happened in a scene from the movie. Perfect Sense.

While Contagion -directed by Steven Soderbergh and curiously released 10 years ago- recounts the unstoppable advance of an infectious disease around the world with surprising similarity to our current pandemic, David Mackenzie's film and also starring actor Ewan McGregor addresses the ravages caused by a virus in our senses and the emotional tsunami that invades after the sensory blackout.

Views in the distance, these movies look more like a documentary. Because if there is something that the pandemic demonstrated, it is that our reality ended up surpassing fiction. Despised for centuries by philosophers, ignored by scientists, and usually belittled in the Pantheon of the senses, smell was vindicated in this pandemic year. Thousands of people had to lose it to finally value it. Anosmia, that is, the sudden loss of the ability to smell, exposed how important this faculty is in our lives: when noses are turned off, in a way the world also turns off.

It is estimated that around 77% of people with covid lose their sense of smell and taste. Most get it back in two to four weeks. But not all. A significant number of people - 10% are believed - yet another surprise awaits. One more, an uncomfortable sequel. In further proof of its destructive power, the coronavirus not only steals the senses; it also deforms them.

A world smelling of smoke

Future historians of the Covid-19 pandemic will surely be struck by how the social perception of this disease was mutating: from pneumonia in an unknown corner of the world, it was considered by some to be a simple flu lasting only two weeks to a most mysterious infection that we still do not fully understand.

At the beginning of 2020, three symptoms were known: fever, cough and shortness of breath. But as the cases increased, the list did not stop growing. In addition to those who lost their sense of smell, there were those who had nausea or diarrhea, arrhythmias, or even heart attacks. Many suffered from persistent headaches, blood clots, rashes, and strokes. Others, surprisingly, had no symptoms.

In some cases, the symptoms did not go away. Rather, they persisted for months. This is how they began to speak, first softly and then with greater force, of "long covid" or "prolonged covid": people who report suffering from a constellation of symptoms for a long time, such as shortness of breath, heart palpitations, chest pain, fatigue, mental confusion, insomnia, joint pain and annoying olfactory distortions.

"I woke up and everything smelled the same: burned," recalls Julián. “Like the one you feel when you walk into a room where a while ago someone was smoking and left. Or when toast burns and you return home in the evening and it's still there. At first it was the only thing I perceived. Then I gradually began to smell other things but with that burning smell in the background. From the time I lost my sense of smell until I fully recovered it, a month and a half passed ”.

Other people have reported being constantly assaulted by foul smells such as fish or sewer odors. Previously delicious aromas of cooked garlic and onion suddenly became intolerable. The meat smells rotten and the coffee smells like gasoline.

"One day my friend came to my house, she threw air freshener in my bathroom," said a young woman on Twitter, "and I thought there was something on fire because she smelled smoke."

This rare olfactory anomaly has several names: "troposmia", "dysosmia" or "parosmia", which must be distinguished from another curious distortion called "phantosmia", an olfactory hallucination that occurs when a certain smell is perceived without any odorous stimulus.

"Because very few people before the COVID pandemic have reported anything like parosmia, this olfactory disorder has not been well studied," says researcher Jane Parker from the University of Reading in the UK. "That's why we don't have a lot of historical data."

The discomfort of good news

The first case of parosmia reported in the medical literature is from 1966. "Infectious diseases, especially the flu, can be followed by long parosmias," wrote Danish physician Kaj Zilstorff at the time, who examined women between 35 and 55 years old, who had never had olfactory disturbances before.

"We tried to treat these women with various methods including hormones, vitamins, sedatives and antiepileptics," he explained, "but we found that only blocking the olfactory region with cocaine improved rapidly and the parosmia subsided."

At present, this cocaine treatment is no longer widely accepted. Doctors often prescribe antihistamines, nasal corticosteroids, zinc, vitamin A, and sodium citrate nasal spray. Or they recommend so-called "olfactory training," that is, smelling different aromas, such as essential oils - and pleasant scents like eucalyptus, lemon, and rose - about three times a day for 10 to 15 seconds.

The surprising thing is that despite the discomfort, in reality, this olfactory distortion is a good sign: it indicates that the smell is recovering. "It suggests that nerve cells are making new connections and that we are getting that olfactory tissue regenerated and getting back to normal," says Justin Turner, medical director of the Smell and Taste Center at Vanderbilt University Medical Center.

Parosmia, seen in this way, is the final stage of internal destruction caused by the virus. Once in the body, the coronavirus is thought to kill olfactory neurons that are used for smelling and that carry signals from receptors in the nose to the terminals of the olfactory bulb in the brain. Hence the anosmia or olfactory silencing. But as these nerve cells recover, they grow back and connect to the brain. Although in certain cases, they do not do it quite well.

"Instead of being wired so that a lemon smells like lemon, the neurons drift a bit and don't connect correctly," says geneticist Danielle Reed of the Monell Chemical Senses Center in Philadelphia, United States. "So the brain is confused about how to interpret that information."

Otolaryngologist Donald Leopold of the University of Vermont compares parosmia to playing a piano with few keys. “Let's imagine that normally, a smell, say pink, touches six keys or neurons. If you contract the coronavirus and it kills some of those nerve cells, let's say you only have three of those neurons left, that no longer allows you to smell a rose correctly. "

This is understood by knowing that the perception of an odor is not produced by a type of molecule. The aromas are usually cocktails, mixtures of up to hundreds of volatile compounds. The smell of coffee, for example, is the result of up to a thousand different chemical compounds. Although we may not see it, it contains sulfur that smells good in combination with all the other molecules that give coffee its pleasant aroma, but not so much when it is smelled alone. They also include methanethiol, an organic compound responsible for bad breath and the bad smell of flatulence.

The hypothesis is that people with parosmia only perceive some of the volatile compounds that a substance contains and that smell bad in isolation.

Faced with this temporary situation, the English organization AbScent recommends consuming food at room temperature or cold; avoid fried foods, roast meats, onions, garlic, eggs, coffee, and chocolate, and try bland foods like rice, noodles, unroasted bread, steamed vegetables, and plain yogurt.

How long it may take for recovery differs from person to person. Most people smell good again in two to four weeks., but a smaller percentage live with this olfactory dysfunction for several months. Enough time to appreciate, perhaps for the first time in their lives, a meaning so ignored, capable of making us travel without moving and awakening long-forgotten memories.