December 1, 2020

Coronavirus: Is it in the brain?

Coronavirus has taken over the world, causing most of the world’s population to self-quarantine and resulting in over 6.4 million cases and 300,000 deaths worldwide. Its symptoms include fever, chills, cough, difficulty breathing, headaches, loss of taste and smell, sore throat, or diarrhea. It takes anywhere from 2-14 days for symptoms to develop and the virus to incubate. It mainly spreads through direct person to person contact – usually when someone sneezes or coughs. In order to prevent this direct contact, social distancing orders have been put into effect so that there is a reduced chance of spreading the virus. It can also spread indirectly by touching an object that an infected person has touched and then touching your mouth although it is not the main reason behind the explosive spread.

Recent research has suggested that coronavirus may have effects on the nervous system. In a study looking at serious COVID cases from China, researchers found that around 40% of patients had neurological symptoms often in the absence of “normal” symptoms. Scientists are not yet sure if these symptoms are the result of an underlying issue, the virus itself, or as a result of the stress on the body after contracting the virus.

Since one of the main symptoms of COVID is the loss of smell and taste, scientists suspect that this was a result of the virus affecting the nerves in the nervous system. Furthermore, similar neurological symptoms such as headaches, disorientation, or seizures were more common as the illness progressed and became more severe in most cases.

Researchers are also studying whether the virus’s effect on the nervous system could be a reason as to why younger people with no existing conditions are developing severe cases of COVID. A similar virus, SARS, which shares a comparable structure and infection mechanism also affects the nervous system and was found in the brain stem which controls breathing.

The SARS coronavirus binds to cells through ACE2 receptors which are found in the respiratory system (the nose, lungs, etc.) but not in the nervous system, implying that the SARS virus entered the brain from another cell in the body. Studies of the virus in mice provided evidence that the virus entered the nervous system through the olfactory nerves. Although it has not yet been shown that a similar process occurs in coronavirus, based on the similarities between the two diseases, it is likely that there is an analogous mechanism.

Scientists are also investigating the role of inflammation in the cause of neurological symptoms. Since it has already been established that there is a strong inflammatory response where the body creates innumerable cytokines in COVID patients, it is highly likely that this inflammation has the possibility to affect the brain.

COVID-19 also has caused an increased number of strokes even in younger patients most likely due to the significantly higher risk of blood clots after contracting the disease. It is still unclear as to what exactly is causing the strokes as they are also caused by severe diseases and infections, age, and underlying health issues.

One such experiment that scientists are performing to determine the exact impact that COVID-19 is happening at MIT in the Tsai lab. Researchers are using a “miBrain” chip that models the blood-brain barrier complete with astrocytes, endothelial cells, and other glial cells. It also mimics the permeability which allows scientists to determine which particles would be able to cross the blood-brain barrier. In regards to COVID, researchers are testing whether the virus can permeate the BBB in all patients or if it varies as well as whether viral entry increases after the cytokine storm caused by the immune system.

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