20th Aug 2020
20th Aug 2020
Curated by Endre Szvetnik
There is mounting evidence that the novel coronavirus is highly contagious because it can infect us through cells in an easy-to-reach part of the nose.
A recent paper has found a 200-700 times larger concentration of the key ACE-2 enzyme in cells in the section of the nasal airway called the olfactory epithelium than in other cells. ACE-2 is the entry point of the virus into our organism. Not all of our cells carry this enzyme, so areas, where it is highly concentrated, are the places where the virus can easily start infecting us. Researchers discovered the abundance of ACE-2 in the nose by investigating why so many COVID-19 patients lose their sense of smell. The olfactory epithelium was a good starting point as this is the section of the nose responsible for detecting smells. The team compared the concentration of ACE-2 in human nasal tissue to cells in the human windpipe, to identify where the infection was more likely to occur. The striking difference of ACE-2 concentrations between the upper and lower airways (much more ACE-2 expressed in the upper airways) suggest the olfactory epithelium is the main route where the virus enters the body.
Is there solid proof of it and what can we do with this knowledge? The findings need to be reliably confirmed by further research. However, several papers that appeared at an earlier stage of the pandemic have already suggested the nose as a primary route for the virus into our bodies. A research paper from March identified a subgroup of the above mentioned nasal epithelial cells – so-called nasal goblet and ciliated cells – as ones with the highest ACE-2 concentrations. It also highlighted the high expression of a protein, TMPRSS2 in the same cells, which plays a key role in helping the virus penetrate into human cells. All this suggests that the easily accessible upper part of the nasal airway is where SARS-CoV-2 largely establishes its foothold. Researchers hope that this knowledge can help us design prevention strategies and therapies. For example, by administering antiviral drugs directly through the nose could help stop the infection and prevent transmission of the virus from the infected individual to other people.
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