Anosmia, a temporary loss of smell, has emerged as one of the defining neurological symptoms of COVID-19 but until recently no one has been able to explain the phenomenon.

Furthermore, there are fears that for some, the damage may be permanent, with one study saying that one in ten coronavirus patients who lost their sense of smell won’t get it back.

According to Dr. Jane Parker, an associate professor of flavor chemistry at the University of Reading, and Dr. Simon Gane, a rhinologist at the University of London, coronavirus patients may be losing their sense of smell from the “cleft syndrome” – when inflamed tissue and mucus block the olfactory cleft.

When the swelling goes down, the passageway to the olfactory neurons opens up and smell is regained. But some patients have a more aggressive inflammation response which can lead to tissue damage and a longer-lasting loss of smell.

However, the good news is that recently, an international team of neuroscientists at Harvard Medical School has found that surprisingly, the sensory neurons that relay the sense of smell to the brain are not among the cell types vulnerable to infection by SARS-CoV-2.

Instead, SARS-CoV-2 is infecting cells that provide support to olfactory sensory neurons, cell receptors called ACE2 which are found in the nose, as well as the throat, lungs, gastrointestinal system and heart.

According to the researchers, this is good news for those who still haven’t regained their sense of smell. The fact that olfactory neurons aren’t directly affected by the coronavirus means that permanent damage to olfactory neural circuits is unlikely.

“Our findings indicate that the novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of supporting cells,” said senior study author Sandeep Robert Datta, associate professor of neurobiology in the Blavatnik Institute at HMS.

“I think it’s good news, because once the infection clears, olfactory neurons don’t appear to need to be replaced or rebuilt from scratch.”

“Anosmia seems like a curious phenomenon, but it can be devastating for the small fraction of people in whom it’s persistent. It can have serious psychological consequences and could be a major public health problem if we have a growing population with permanent loss of smell.”

It should be noted that as coronavirus patients begin to regain their sense of smell, many develop what is called “parosmia” – a distorted sense of smell, with some people experiencing pleasant smells as metallic or burning odors.

Kelsey Meeks, an attorney in New Orleans, lost her senses of smell and taste due to COVID-19 in early April and still hasn’t regained them back three months later, although she is slowly beginning to smell a whiff here or there and can taste the difference between salty and sweet, a report by Business Insider (BI) said.

“I don’t wear perfume anymore because it’s just too depressing to spray it on every morning and not be able to smell it,” Meeks told BI. “Sometimes I can pick up a whiff of it, but the part I can smell now smells awful.”

Meeks is happy that she seems to be on her way to regaining her senses of smell and taste but says that the stress of worrying about whether she’ll fully regain them has been difficult for her, especially the thought of not being able to enjoy the taste of food.

“The impact of not being able to experience those things anymore feels like I’ve suffered a much bigger loss than just my senses,” Meeks said. “It’s a reminder multiple times a day that I had COVID-19 and that it still has me.”

(YWN Israel Desk – Jerusalem)