Why people with COVID-19 may lose their sense of smell

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In a new study, researchers have discovered the reason why so many people with COVID-19 lose their sense of smell, even when they have no other symptoms.

They studied tissue removed from patients’ noses during surgery.

In their experiments they found extremely high levels of angiotensin-converting enzyme II (ACE-2) only in the area of the nose responsible for smelling.

This Enzyme is thought to be the ‘entry point’ that allows coronavirus to get into the cells of the body and cause an infection.

The findings offer clues as to why COVID-19 is so infectious and suggest that targeting this part of the body could potentially offer more effective treatments.

The research was conducted by a team at Johns Hopkins University School of Medicine.

The team used tissue samples from the back of the nose of 23 patients, removed during endoscopic surgical procedures for conditions such as tumors or chronic rhinosinusitis, an inflammatory disease of the nose and sinus.

They also studied biopsies from the trachea (windpipe) of seven patients. None of the patients had been diagnosed with coronavirus.

They found by far the most ACE2 on the lining cells of the olfactory epithelium, the area at the back of the nose where the body detects smells.

The levels of ACE2 in these cells was between 200 and 700 times higher than other tissue in the nose and trachea, and they found similarly high levels in all the samples of the olfactory epithelium, regardless of whether the patient had been treated for chronic rhinosinusitis or another condition.

ACE2 was not detected on olfactory neurons, the nerve cells that pass information about smell to the brain.

The team says they saw that the levels of ACE2—the COVID-19 ‘entry point’ protein were highest in the part of the nose that enables us to smell.

These results suggest that this area of the nose could be where the coronavirus is gaining entry to the body.

They are now doing more experiments in the lab to see whether the virus is indeed using these cells to access and infect the body.

If that’s the case, they may be able to tackle the infection with antiviral therapies delivered directly through the nose.

One author of the study is Professor Andrew P. Lane, director of the division of rhinology and skull base surgery.

The study is published in the European Respiratory Journal.

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