Scientists could be closer to understanding one of the most common symptoms of even mild covid-19: the loss of smell and taste. New Study Suggests Novel Infection coronavirus can damage important cells that support nerve cells responsible for transmitting odor to the brain
Partial or total loss of smell, also known as anosmia, is occasionally caused by many respiratory infections, including covid-19. There are even some evidence that anosmia is a more accurate predictor of having covid-19 than other known symptoms like fever or dry cough.
However, a mystery that has endured is exactly how covid-19 leads to anosmia. This new study, published in Science Advances over the weekend, it’s one of the first attempts to figure that out.
The researchers looked at the cells that line our nasal cavity, including those in the upper region of the nose that houses the olfactory nerve. The olfactory nerve is the set of nerve fibers that are the first to receive information about odors from the outside world, through receptors that react to various chemical compounds that we know as aromas. These fibers then send that information to the brain, where it is processed in our perception of smell.
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In the tissue area where the olfactory nerve is located, the researchers found that the cells expressed two key proteins for the coronavirus, ACE2 and TMPRSS2. The virus hijacks the receptors for these proteins as a way to enter and infect new cells. But other experiments showed that, surprisingly, it was not the nerve cells that expressed ACE2; was their supporting cast. Specifically, these were two types of non-nerve cells: the sustain cells, which physically support and provide energy to the olfactory nerve, and the basal cells, the stem cells that replace damaged cells in that area.
“Our findings indicate that the new coronavirus changes the sense of smell in patients by not directly infecting neurons but by affecting support cell function,” said study lead author, Sandeep Robert Datta, a neurobiologist at Harvard Medical School. , in a statement published by the university.
That’s somewhat surprising, since other viruses that cause anosmia, including other coronaviruses, tend to directly infect olfactory nerve cells. Ideally, that could also be good news for covid-19 survivors, as indirect damage to our tracking process should be less likely to result in the long term. loss of smell, the authors said. It is also compatible with other evidence that suggests the brain is rarely directly attacked. by the coronavirus. But it is still too early to rule out that our olfactory nerve cannot be permanently damaged by covid-19 (one of the various theories of the authors is that the damage to these supporting cells is still enough to kill the olfactory nerve cells). And there has been reports of people being unable to smell long after your initial infection has subsided.
Even if only some people get COVID-19 suffer anosmia long-termThe authors noted that this still leaves many survivors potentially at risk for a truly tragic deficit. By some estimates, one-third to two-thirds of people with symptoms of covid-19 experience anosmia.
“Anosmia seems like a curious phenomenon, but it can be devastating for the small fraction of people in whom it is persistent,” Datta said. “It can have serious psychological consequences and it could be a major public health problem if we have a growing population with permanent loss of smell.”
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