Not a biologist, but reading the paper, the chain of reasoning appears to be summarized in this section:<p>> <i>Taken together, the neuroinvasive propensity has been demonstrated as a common feature of CoVs. In light of the high similarity between SARS-CoV and SARS-CoV2, it is quite likely that SARS-CoV-2 also possesses a similar potential. Based on an epidemiological survey on COVID-19, the median time from the first symptom to dyspnea was 5.0 days, to hospital admission was 7.0 days, and to the intensive care was 8.0 days 15. Therefore, the latency period is enough for the virus to
enter and destroy the medullary neurons. As a matter of fact, it has been reported that some patients infected with SARS-CoV-2 did show neurologic signs such as headache (about 8%), nausea and vomiting (1%).</i><p>There's also this rather disquieting anecdote used as evidence of a link to the nervous system:<p>> <i>According to the complaints of a survivor, the medical graduate student (24 years old) from Wuhan University, she
must stay awake and breathe consciously and actively during the intensive care. She said that if she fell asleep, she might die because she had lost her natural breath.</i><p>Supposing that this neurological link is real,<p>> <i>the precaution with masks will absolutely be the most effective measure to protect against the possible entry of the virus into the CNS. It may also be expected that the symptoms of the patients infected via facal-oral [sic?] or conjunctival route will be lighter than those infected intranasally. The possible neuroinvasion of SARS-CoV-2 may also partially explain why some patients developed respiratory failure, while others not. It is very possible that most of the persons in Wuhan, who were the first exposed to this previously unknown virus, did not have any protective measure, so that the critical patients is much more in Wuhan than in other cities in China.</i><p>So let me ask a dumb question for someone with actual biomedical knowledge. Are they saying that infection of the CNS is somehow easier through the nose, in which case high-quality face masks actually do matter?<p>I'm also confused by this sentence in the introduction, which appears to contradict the hypothesis that the upper respiratory tract is a high-impact area?<p>> <i>However, different from SARS-CoV, SARS-CoV-2-infected patients rarely showed prominent upper respiratory tract signs
and symptoms, indicating that the target cells of SARS-CoV-2 may be located in the lower airway.</i><p>I will note that, unlike some other papers on this topic, this one has been peer-reviewed in what seems to be a legitimate medical journal (Journal of Medical Virology), so there should be some genuine substance here.