Fully a third of all people with Covid-19 report neurological symptoms such as loss or change in their sense of smell or taste, headaches, fatigue, dizziness, and nausea. There’s been clear evidence of the SarsCoV2 virus being present in brain tissue, but the question has been how did the virus jump from the respiratory tract to the brain.
Recent research just published in the Journal Nature by Dr. Helena Radbruch of Charité's Department of Neuropathology, Dr. Frank Heppner, and a multidisciplinary team of researchers has now traced how the virus enters the central nervous system and subsequently invades the brain.
SarsCoV2 spike protein was found in certain types of cells within the olfactory mucous layer, where it may exploit the proximity of endothelial and nervous tissue to gain entry to the brain. Evidence suggested that olfactory sensory neurons may be directly infected, as well as in the brain areas that receive smell and taste signals. Which can explain a wide range of the well-documented neurological symptoms in Covid-19, including alterations of smell and taste perception well after recovery from the respiratory-phase of the disease.
Interestingly, SarsCoV2 was also found in other areas of the nervous system, including the medulla oblongata, the primary respiratory and cardiovascular control center of the brain. Researchers suggest this could exacerbate impact on respiratory function, adding to breathing problems due to SARS-CoV-2 infection of the lungs.
Quotes from the Lead Researcher
From Dr. Helena Radbruch:
These data support the notion that SARS-CoV-2 is able to use the olfactory mucosa as a port of entry into the brain," says Heppner. This is also supported by the close anatomical proximity of mucosal cells, blood vessels, and nerve cells in the area. "Once inside the olfactory mucosa, the virus appears to use neuroanatomical connections, such as the olfactory nerve, in order to reach the brain.
It is important to emphasize, however, that the COVID-19 patients involved in this study had what would be defined as severe disease, belonging to that small group of patients in whom the disease proves fatal. It is not necessarily possible, therefore, to transfer the results of our study to cases with mild or moderate disease.
Our data suggest that the virus moves from nerve cell to nerve cell in order to reach the brain. It is likely, however, that the virus is also transported via the blood vessels, as evidence of the virus was also found in the walls of blood vessels in the brain.
SARS-CoV-2 is far from the only virus capable of reaching the brain via certain routes. Other examples include the herpes simplex virus and the rabies virus.
In our eyes, the presence of SARS-CoV-2 in nerve cells of the olfactory mucosa provides good explanation for the neurologic symptoms found in COVID-19 patients, such as a loss of the sense of smell or taste.
We also found SARS-CoV-2 in areas of the brain which control vital functions, such as breathing. It cannot be ruled out that, in patients with severe COVID-19, presence of the virus in these areas of the brain will have an exacerbating impact on respiratory function, adding to breathing problems due to SARS-CoV-2 infection of the lungs. Similar problems might arise in relation to cardiovascular function.
Additional Scientific References
Research Paper from the Journal Nature:
Olfactory transmucosal SARS-CoV-2 invasion as a port of central nervous system entry in individuals with COVID-19
Reporting from Genetic Engineering News:
SARS-CoV-2 May Enter the Brain through the Nose
About the author:
I am a scientist with 20+ years in the biotech industry. I currently work as a consultant with companies involved in developing molecular diagnostics platforms, including some of the key testing platforms used to detect the SarsCoV2 virus.
So I bring an insider’s perspective that is scientifically oriented but directed to a general audience trying to make sense of the conflicting stories surrounding the Covid pandemic.
To learn more: https://www.linkedin.com/in/dalewharrison/
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