COVID-19 may remain in people’s brains after infection and trigger relapses in patients who believed they recovered, according to a new, peer-reviewed study published in the journal Viruses.

The Georgia State University study found that mice, when infected with the virus through their nasal passages, developed severe illnesses due to brain infections, even after the virus departed their lungs.

“It’s scary,” the study’s lead author and researcher Mukesh Kumar noted before adding that “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.”

Kumar also noted how the virus primarily affected the brain, as the study found COVID-19 to be concentrated at a level that was 1,000 times greater than in any other part of the body:

“The brain is one of the regions where virus likes to hide. 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 also notes that “COVID-19 survivors whose infections reached their brain are also at increased risk of future health problems, including auto-immune diseases, Parkinson’s, multiple sclerosis and general cognitive decline.”