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Autopsies of 33 patients who died from Covid-19 revealed traces of viral material in the brain, which appears to come from the nose. While these are preliminary findings, they are rather worrying.
The evidence is piling up
The upper part of the human nasal cavity, known as the nasopharynx, is believed to be one of the earliest sites of infection and replication of the SARS-CoV-2and it could also be a weak point in our brain defenses. Although the latter is separated from the rest of the body’s bloodstream by a semipermeable barrier of cells, called the blood-brain barrier, designed to protect our precious neurons from toxins and pathogens, some particularly subtle viruses are able to cross it. Which would be the case with SARS-CoV-2.
Some scientists even believe that this invasion route could be the cause of many associated neurological symptoms COVID-19including loss of smell and taste, headache, dizziness, nausea and severe fatigue.
Recently, several studies have identified traces ofARN virus in the brain and cerebrospinal fluid of some patients with COVID-19, suggesting that the virus’s spike proteins promote inflammation in the endothelial cells and the brain barrier, which would create a breach that would allow the virus to reach the central nervous system.
Viral RNA found in the top of the nose and in different areas of the brain
Published in the magazine Nature Neuroscience, this new work suggests another possible path. During their analyzes, the researchers not only found intact viral particles in the endothelial cells of the nasopharynx, but also in theARN viral in the upper part of the nose (mucosa) and in different regions of the brain. The genetic material detected was minimal, but the study authors recall that autopsies occurred on average one month after deaths.
Although it is not possible to see how the virus travels inside the brain, in some patients the spike proteins present on the surface of the brain SARS-CoV-2 they were also found in cells that the researchers identified as neurons. This suggests that the virus may somehow cross the blood-brain barrier and enter the brain via the long, threadlike projections of the olfactory nerves.
Consider several avenues of invasion
But even if it turns out that neurons in the nose carry the SARS-CoV-2 to the brain would probably just be an entry point. The researchers found that some brain regions with traces ofARN they had no direct connection to the olfactory mucosa and were more involved in respiration and cardiovascular control, suggesting that the virus also enters it through another means.
This could pass through endothelial cells, as suggested by other studies, or attach to another cell type that is authorized to cross the blood-brain barrier, particularly to carry essential resources.
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