Study: Persistent COVID-19 Smell Loss Linked to Virus Hiding in Nasal Cavities

Published in the journal Science Translational Medicine, the study, carried out on eleven patients and also on golden Syrian hamsters, reveals that RT-PCR tests can give negative results, while the virus is lodged at the bottom of the nasal cavities, in the olfactory mucosa. It would therefore be indicated to perform a nasal brushing, in addition to the nasopharyngeal sampling, in patients with a loss of smell in order to better diagnose Covid-19, notes the study.

"According to our results, the loss of smell can persist for several months in some Covid-19 patients, and this persistence of clinical signs is attributable to the persistence of the virus and inflammation in the olfactory mucosa," explains Marc Lecuit (Pasteur, Inserm, AP-HP), co-author of the study.

The researchers performed nasal brushing on seven less severe Covid-19 patients who had reported a loss of smell. The results indicate that the virus had taken refuge in the olfactory neurons, immune cells and other types of cells in the olfactory mucosa, causing inflammation and cell death. Four other patients suffering from long-term loss of smell that the PCR test could not detect also underwent this analysis.