Anosmia is the loss of the sense of smell – and since the start of the pandemic, it has been one of the main known symptoms of COVID-19. The reason behind this mechanism is unknown… until now, that is.
The lack of smell is very vexing and frustrating to a lot of people who have had COVID-19, and the path to recovery can take a long time.
“Fortunately, many people who have an altered sense of smell during the acute phase of viral infection will recover smell within the next one to two weeks, but some do not,” said author Bradley Goldstein in a statement, “We need to better understand why this subset of people will go on to have persistent smell loss for months to years after being infected with SARS-CoV2.”
Researchers have found that there is an ongoing immune assault on olfactory nerve cells, and this is associated with a decline in the cells.
This study took olfactory epithelial (the tissue in the nose where the smell nerve cells are located) samples from 24 biopsies, nine from people that had long-term smell loss. Single-cell RNA sequencing and immunohistochemistry were conducted on the samples. It was found the nine smell-loss samples contained fewer olfactory sensory neurons than the controls. This reduction may have been because of damage to the tissue from ongoing inflammation.
Also, the results revealed that there was a widespread infiltration of T-cells engaged in the inflammatory epithelium.
“The findings are striking,” Goldstein said. “It’s almost resembling a sort of autoimmune-like process in the nose.”
“We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help to at least partially restore a sense of smell,” Goldstein said, noting this work is currently underway in his lab.
Despite the small sample size, the research outcomes seem promising, and the mechanisms behind the lack of smell could also explain other long COVID-19 symptoms, such as brain fog, generalized fatigue, and shortness of breath.
This work was published in the Science Translational Medicine.
Source Link: Finally, We May Have Found A Reason For Smell Loss In Long COVID-19