A study published Monday in the journal Nature revealed strong evidence that a mild COVID-19 infection can cause brain tissue damage and other neurological irregularities.

The large study is the first to include patients who endured brain scans before and after contracting COVID-19, The New York Times noted. The study included 785 participants aged 51 to 81.

"We were quite surprised to see clear differences in the brain even with mild infection," Gwenaëlle Douaud, associate professor of neurosciences at the University of Oxford and the study's lead author, told CNN.

Researchers found brain tissue damage, particularly in parts connected to the sense of smell. All participants engaged in two brain scans around three years apart. Participants infected with COVID displayed more cognitive decline between the two points in time.

Yale School of Medicine immunologist Dr. Akiko Iwasaki conducted a study in January to discover potential long-term effects of COVID, finding that even those who endured milder symptoms from the virus can possibly experience long-term neurological damage.

"Our most recent research was done mostly in [a] mouse model of COVID-19, where we intentionally gave mice a mild respiratory infection with SARS-CoV-2,” Iwasaki said. “We measured what happens in the brain seven days and seven weeks after the infection. And what we found is that even with a very mild infection ... we still saw some significant damage in the cells of the brain."

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