Nose is a point of entry for coronavirus as West reinforces early Chinese research
- European team builds on Chinese findings from patient’s nose sample
- Nasal vulnerability means masks are crucial protection for medical staff and the public
The question, which seems simple enough for a child to answer, took a big research team involving nearly 100 health research institutes in the West months to find out.
And the answer is yes, according to a paper published in the journal Nature Medicine on Thursday.
The question was first raised by Chinese scientists after the first viral strain was isolated and identified in Wuhan early this year. Chinese researchers, including Professor Zuo Wei of Tongji University in Shanghai, found the cells producing ACE2 – a receptor binding protein targeted by the coronavirus – occurred mainly in some organs lower down in the human body, such as lungs, intestines and testicles.
Their findings seemed to coincide with the fact that in the early stage of disease onset Covid-19 patients had relatively mild symptoms in the upper airway. There was even speculation that this infectious disease might start from inside, such as in the stomach and lower parts of the lungs, before devastating the rest of the body.
But Professor Zheng Min, of the National Clinical Research Centre for Infectious Diseases at Zhejiang University, investigated further and found ACE2 expressing cells in nasal tissue, as well as a higher load of the virus in a patient’s nose samples than found in oral swabs.
Her discovery in early February helped Chinese health authorities strengthen the protection of health care workers and citizens with more stringent policies, including the mandatory use of face masks in public areas.
But the finding was based on the sample of one Asian donor. Whether the results could be repeated in other populations, such as Europeans, needed more investigation.
The new study led by Dr Waradon Sungnak, a postdoctoral fellow at the Wellcome Sanger Institute in Cambridge, Britain, had similar findings to the Chinese study by analysing data from a larger sample base.
Sungnak’s team found that the ACE2 expression in the nose could indeed be higher than other parts of the respiratory system, such as the mouth and throat, making the nose a possible entry point for the coronavirus.
The researchers cultured the nose epithelial cells and checked their ACE2 expressions. The results confirmed their estimate.
They also checked the ability of different viruses to infect the nose. They found strains with a higher ability could send more widely in communities. Mers, for instance, had weaker nose-entry efficiency than Sars-CoV-2. It might have limited the virus’ spread to only a few regions.
The Cambridge-led study did not cite the research by Zheng’s team. There was no mention of the earlier discovery of ACE2 expressing cells in the nose after the outbreak of Covid-19.
The quality of the Chinese study “was not at the standards that we were comfortable to cite or rely on scientifically”, Sungnak said in reply to queries from the South China Morning Post.
“For example, it lacked appropriate quality control steps and proper identification of the cell types done in single-cell RNA sequence analysis,” he added.
Zheng did not immediately respond to a request for comment.
