According to a studythe novel coronavirus may make its entry to the human brain through the nose.

The findings intended to understand the reason behind the neurological symptoms of the novel coronavirus.

The study, published in the journal Nature Neuroscience and carried by the researchers from Charite-Universitatsmediz in Berlin, Germany, found that Covid-19 not only attacks the respiratory tract but also impacts the central nervous system.

This causes neurological issues such as loss of taste and smell, headache, fatigue, and nausea.

“There is increasing evidence that SARS-CoV-2 not only affects the respiratory tract but also impacts the CNS, resulting in neurological symptoms such as loss of smell and taste, headache, fatigue, nausea, and vomiting in more than one-third of individuals with Covid-19,” the study read.

Methodology

For the study, the researchers examined the nasopharynx — the upper part of the throat that connects to the nasal cavity — a likely first site of viral infection and replication, and the brains of 33 patients — 22 males and 11 females —who died with the coronavirus infection.

The median age at the time of death was 71.6 years, and the time from onset of Covid-19 symptoms to death was a median of 31 days.

Findings

The researchers observed the presence of SARS-CoV-2 RNA, the genetic material of the coronavirus, and protein in the brain and nasopharynx. The intact virus particles were also detected in the nasopharynx.

The researchers revealed that the highest levels of viral RNA were found in the olfactory mucous membrane.

Notably, the duration of the infection was inversely correlated with the amount of detectable virus. This indicated that higher SARS-CoV-2 RNA levels were found in cases with shorter disease duration.

The team also found SARS-CoV-2 spike protein in certain types of cells within the olfactory mucous layer. The researchers speculated that the virus also exploits the proximity of endothelial and nervous tissue to gain entry to the brain.

In some patients, SARS-CoV-2 spike protein was found in cells expressing markers of neurons, suggesting that olfactory sensory neurons may be infected, as well as in the brain areas that receive smell and taste signals, the researchers said.

SARS-CoV-2 was also found in other areas of the nervous system, including the medulla oblongata — the primary respiratory and cardiovascular control center of the brain, they said.

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