COVID-19 May 'Hide' in Brains and Cause Relapses, Study Says

A new study suggests that the coronavirus that causes COVID-19 may hide in the brain of those infected and cause relapses in patients who had seemed to be recovering.

In a study published Tuesday by the journal Viruses, researchers from Georgia State University found that mice infected with the virus through their nasal passages developed severe illness due to brain infection even after the virus had left their lungs. Lead researcher and study co-author Mukesh Kumar suggested that the findings could explain why human patients who appear to be nearly over the illness sometimes quickly relapse and die.

"The brain is one of the regions where virus likes to hide," Kumar said in a press release. "That's why we're seeing severe disease and all these multiple symptoms like heart disease, stroke and all these long-haulers with loss of smell, loss of taste ... All of this has to do with the brain rather than with the lungs."

The study found that the virus was located in the brains of mice at a level 1,000 times higher than any other area of the body. While levels of the virus located in the lungs began to diminish after three days of infection, the virus remained at high levels in the brain on the fifth and sixth days, when the course of the disease became more severe.

"Our thinking that it's more of a respiratory disease is not necessarily true," Kumar said. "Once it infects the brain it can affect anything because the brain is controlling your lungs, the heart, everything. The brain is a very sensitive organ. It's the central processor for everything."

COVID-19 Brain Study
This conceptual 3D illustration shows the COVID-19 coronavirus infecting a person's brain. Design Cells/Getty

In addition to COVID-19, Kumar suggests that the coronavirus reaching the brain could leave patients susceptible to other serious health issues in the future, including neurological conditions like Parkinson's Disease and Multiple Sclerosis, along with general cognitive decline and autoimmune diseases.

"It's scary," he said. "A lot of people think they got COVID and they recovered and now they're out of the woods. Now I feel like that's never going to be true. You may never be out of the woods."

Neurological symptoms are known to be relatively common for people with COVID-19. However, while multiple studies have suggested that mice brains are susceptible to being infected by the virus, research has not produced conclusive evidence to support the notion that the virus infects and concentrates in human brains. Neurological symptoms could be caused by an immune response rather than a direct brain infection.

A blog post written by National Institutes of Health Director Dr. Francis Collins last week detailed a recent study conducted by the National Institute of Neurological Disorders and Stroke that found brain damage in tissue samples from 19 people who had died from COVID-19 but no evidence that the virus had infected the brain tissue itself.

"The findings are especially intriguing because there has been some suggestion based on studies in mice that SARS-CoV-2 might cross the blood-brain barrier and invade the brain," Collins wrote, before noting that another study, published in the Journal of Experimental Medicine, had found evidence of the virus in the brains of three people who died from COVID-19 complications.

"Clearly, more research is needed," Collins added. "As we learn more about the many ways COVID-19 wreaks havoc on the body, understanding the neurological symptoms will be critical in helping people."