Lost sense of smell is the most common phenomena these days . The Covid-19 affectees even after their recovery suspiciously cant smell nothing, nothing at all.

Smell lost is more accurate predictor than fever or other symptoms

An approximate 80% of patients with COVID-19 have odor problems, and many also have dysgeusia or ageusia (disruption or lack of taste, respectively) or chemesthesia changes (the ability to sense chemical irritants such as hot chilies). In persons with the illness, smell deficiency is so widespread that some scientists have recommended its use as a screening test because it could be a more accurate predictor than fever or other symptoms.

Dysgeusia, also known as ageusia, is a distortion of the sense of taste.

Reason behind smell loss

Physicians and researchers worried early in the pandemic that COVID-19 related anosmia would signal the virus to make its way through the nose into the brain, where it might cause significant and permanent damage. Via the olfactory nerves that detect smells in the air and relay these signals to the brain, a suspected path would be. But tests have shown that this is definitely not the case, says Harvard Medical School neuroscientist Sandeep Robert Datta.

“We don’t fully understand what those changes are yet, however,” Datta said. “Sustentacular cells have largely been ignored, and it looks like we need to pay attention to them, similar to how we have a growing appreciation of the critical role that glial cells play in the brain.”

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A cartoon of the olfactory bulb and epithelium. Cells of note – Top right: A pericyte (light orange) wraps around a blood vessel (red). Bottom right: Olfactory sensory neurons (light red, orange) surrounded by sustentacular cells (tan) and basal cells (yellow and light orange). Image: Brann et. al., 2020.

The findings also offer intriguing clues into COVID-19-associated neurological issues. The observations are consistent with hypotheses that SARS-CoV-2 does not directly infect neurons but may instead interfere with brain function by affecting vascular cells in the nervous system, the authors said. This requires further investigation to verify, they added.

The study results now help accelerate efforts to better understand smell loss in patients with COVID-19, which could in turn lead to treatments for anosmia and the development of improved smell-based diagnostics for the disease.

“Anosmia seems like a curious phenomenon, but it can be devastating for the small fraction of people in whom it’s persistent,” Datta said. “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.”

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The team also hope the data can help pave inroads for questions on disease progression such as whether the nose acts as a reservoir for SARS-CoV-2. Such efforts will require studies in facilities that allow experiments with live coronavirus and analyses of human autopsy data, the authors said, which are still difficult to come by. However, the collaborative spirit of pandemic-era scientific research calls for optimism.

“We initiated this work because my lab had a couple of datasets ready to analyze when the pandemic hit, and we published an initial preprint,” Datta said. “What happened after that was amazing, researchers across the globe offered to share and merge their data with us in a kind of impromptu global consortium. This was a real collaborative achievement.”

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