Can the coronavirus attack neurons?
Coronaviruses are a family of many viruses that can cause a wide variety of diseases in humans, from the common cold to COVID-19. On the possibility that SARS-CoV-2 also affects the brain, researchers have discovered that these viruses could spread through the olfactory nerve in the central nervous system.
Less specific symptoms of the new coronavirus, such as cough, shortness of breath, and fever, include loss of smell (anosmia) and taste (ageusia). A peculiarity found in a large number of patients infected with SARS-CoV-2 that could suggest that the virus can attack, in addition to the lungs, the nervous system. Researchers at the French National Institute for Scientific Research believe that the evidence supports that it is actually the entire family of human coronaviruses, which is likely the cause of a wide range of diseases ranging from "a cold to a serious lung infection, as well as other respiratory viruses that could reach the brain."
The last ones affirm that the loss of smell could come from an infection of the olfactory neurons. The scientific team has highlighted similar processes in cold coronaviruses, as they explain in an article published in the journal Viruses in January, shortly before the first cases of Covid-19 were identified. "Our research on the neuroinvasive and neuropathogenic power of human coronaviruses suggests that they reach the center of smell located in the brain, primarily using the olfactory nerve as a vehicle," explains Professor Pierre Talbot, who says he has been studying coronaviruses closely for 40 years.
Olfactory neurons, first affected
The first infected neurons would be those in the nasal cavity, which can detect odors. But this loss of smell, although sudden, would be temporary. "Olfactory neurons can regenerate unlike most other neurons in the brain. We could assume a return of smell when new olfactory neurons take over," say the specialists. Then, the neurons in the center of smell could become infected, because they are in direct communication with those in the nasal cavity.
"Neurons can also indicate the presence of a virus so that other cells in the brain and cells of the immune system can help them fight," they said. However, the question arises whether the virus can reach the brain compared to people with weakened immune systems (the elderly, young children, transplant recipients taking anti-rejection medications, etc.). This could, they say, cause acute inflammation of the brain as a result of a viral infection (encephalitis) and cause serious long-term damage.
Can the virus cause multiple organ dysfunction?
"During the writing of our article, we noted that viral encephalitis rarely occurs. For those caused by the herpes virus, for example, we can think of less than one in 10,000 cases," the scientists report. "It's still important to keep in mind when dangerous inflammation occurs: one in two deaths to one in four deaths according to studies. It is still too early to know whether people recovering from Covid-19 will have neurological sequelae as The effects of coronavirus on the nervous system are beginning to be studied, but now they ask that this possibility be considered.
"In mice, we have shown that the cold coronavirus can cause neurodegenerative diseases with similarities to multiple sclerosis and Alzheimer's and Parkinson's diseases." In the case of the SARS (Severe Acute Respiratory Syndrome) epidemic in 2003, the coronavirus responsible also had this type of stroke, "they conclude. In addition to the fact that the scientific community is accumulating data showing that coronaviruses can be harmful For the brain, there are also more and more studies to analyze the possible consequences of the current coronavirus on the heart and kidneys.