Abstract: After the outbreak of the novel coronavirus (SARS-CoV-2), there have been more and more reports on the sequelae of COVID-19. Considering the current news from all over the world, the fight with this virus is not positive, for it may threaten multiple organs, even the brain.

Although mankind has been working together to fight against SARS-CoV-2, and the virus is still spreading and spreading in various countries. And those who survived this catastrophe are still struggling with illness. According to reports, in European and American countries which were hit by the epidemic, more and more recovered patients showed sequelae.

The most common sequela is lung injury. Many patients still have symptoms such as cough and fatigue after they are cured. After returning to work, some people cannot even take short walks due to shortness of breath and muscle aches. The damage to the liver and kidney is also alarming. Experts in the United Kingdom and Canada have also found that 8%-12% of COVID-19 (coronavirus disease) patients receiving intensive care have liver or kidney failure and need to rely on perennial dialysis to survive.

In addition, a research report published by British scientists in The Lancet-Psychiatry also showed that the SARS-CoV-2 may cause many negative effects on the brain, and may even cause stroke or mental illness.

In April 2020, neuroscientists, neurologists, and psychiatrists across the UK entered detailed information on some severely ill patients with COVID-19 in a database and analyzed them. Of the 125 critically ill patients cited in the study report, 77 had interrupted blood flow to the brain, which is usually caused by a blood clot in the brain.Blood clot is a relatively common complication of COVID-19, and many young patients with severe infection also have shown this symptom. The report showed that 37 of the 125 patients had changes in their mental state, such as obvious personality changes and depressive symptoms, or confusion and difficulty in understanding things. Among these patients with altered mental status, 18 patients were under 60 years old.

Clinically, the brain symptoms of patients with COVID-19 are often not noticed. Many patients said that their sense of smell is no longer what it used to be, which is also related to brain damage. A report recently published stated that researchers performed a brain MRI examination on a young female patient with COVID-19 and found that several areas of the patient's brain related to the sense of smell appeared signs of SARS-CoV-2 infection, such as the olfactory bulb and the straight back of the right frontal loberesponsible for processing olfactory signals.

Scientists still don't know how the SARS-CoV-2 harms the brain. Studies have shown that the SARS-CoV-2 can infect pericytes, which are wrapped around blood vessels and can help control blood flow. Pericytes in the brain can help maintain the blood-brain barrier and prevent pathogens from entering. Scientists speculate that the SARS-CoV-2 will invade the brain by damaging pericytes to create a breach in the blood-brain barrier. But this is just a guess, and scientists are conducting more research on the brain tissue of people infected with the SARS-CoV-2 to further confirm it.