Cause of Smell Loss in COVID-19 Patients Uncovered by Scientists

Loss of sense of smell is one of the most common symptoms of COVID-19, but some patients may not fully recover their sense of smell even after they have recovered from the virus.

A recent study led by Duke Health has shed light on the cause of this persistent smell loss and provides important insights into the underlying biological mechanisms of other long COVID-19 symptoms.

The study, published in the journal Science Translational Medicine, analyzed olfactory epithelial samples from 24 biopsies, including nine patients who suffered from long-term smell loss after COVID-19. The biopsy-based approach, using sophisticated single-cell analysis, revealed widespread infiltration of T-cells causing inflammation in the olfactory epithelium, the tissue in the nose where smell nerve cells are located. This immune response persisted despite the absence of detectable SARS-CoV-2 levels and was associated with a decrease in the number of olfactory sensory neurons, possibly due to damage from the ongoing inflammation.

Senior author Bradley Goldstein, M.D., Ph.D., associate professor at Duke, described the findings as “striking” and almost resembling an autoimmune-like process in the nose. He also noted that learning what sites are damaged and what cell types are involved is a crucial step toward designing treatments that could help restore a sense of smell. The researchers were encouraged by the fact that neurons appeared to maintain some ability to repair even after the long-term immune onslaught, and they are hopeful that modulating the immune response or repair processes within the nose of these patients could partially restore a sense of smell.

The findings of this study provide important insights into the cause of persistent smell loss from COVID-19 and offer hope for a potential solution for those affected.