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Why Covid-19 patients lose their sense of smell

CAPE TOWN – A team of researchers may have found the reason behind many Covid-19 patients losing their sense of smell even why no other symptoms are present.

In a recent study published in the European Respiratory Journal, researchers believe they may have found the reason why so many infected Covid-19 patients lose their sense of smell. This is after investigated the removal of tissue from infected patients nose.

The study conducted by Professor Andrew P Lane, the director of the division of rhinology and skull base surgery, Dr Mengfei Chen and colleagues from Johns Hopkins University School of Medicine, with the team discovering extremely high levels of angiotensin-converting enzyme II (ACE-2) in the area of the nose responsible for smelling which is also the enzyme seen as an “entry point” where the coronavirus gets into the cells of the body and then leads to an infection.

Professor Lane said, “I specialise in nasal and sinus problems, so the loss of the sense of smell in Covid-19 is of particular clinical interest to me. While other respiratory viruses generally cause loss of the sense of smell through the obstruction of airflow due to swelling of the nasal passages, this virus sometimes causes loss of smell in the absence of other nasal symptoms.”

With tissue samples they collected, the team of researchers found by far the most ACE2 levels in the olfactory epithelium, which is part of the body responsible for smelling, with between 200 and 700 times higher than other tissue in the nose and trachea.

Dr Chen said: “This technique allowed us to see 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. The olfactory epithelium is quite an easy part of the body for a virus to reach, it’s not buried away deep in our body, and the very high levels of ACE2 that we found there might explain why it’s so easy to catch Covid-19.”

The team of researchers say the findings from their study may suggest targetting that exact part of the body could result in more effective treatments, with Professor Lane adding, “We 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, we may be able to tackle the infection with antiviral therapies delivered directly through the nose.”


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