Scientists Uncover Possible Explanation for Long COVID

Thursday, October 26th, 2023 -- 10:01 AM

(By Will Stone, Wisconsin Public Radio) Scientists have uncovered a possible explanation for one of COVID-19's most vexing legacies: the stubborn neurological symptoms of long COVID, such as brain fog, memory loss and fatigue.

According to Will Stone with the Wisconsin Public Radio, the first clue emerged when researchers scoured the blood of long COVID patients: It was serotonin, specifically, a lack of the neurotransmitter circulating in the body, that grabbed their attention.

Their analysis revealed that having low levels of that chemical predicted whether or not someone was suffering from persistent symptoms following an infection. Next, the team of researchers at the University of Pennsylvania carefully recreated the chain of events that might be depleting serotonin and causing downstream consequences that could line up with some of the symptoms characteristic of long COVID.

Their findings, published in the journal Cell, point to an intriguing hypothesis that winds its way from the gut up through the vagus nerve and ultimately into the brain. "Basically, we can explain some of the neurocognitive manifestations of long COVID through this pathway that leads to serotonin reduction," says Christoph Thaiss, a senior author on the study and an assistant professor of microbiology at the University of Pennsylvania.

The work has made an impression on those studying long COVID, a condition that still has no validated treatment or widely accepted biomarker that doctors can use to diagnose the condition.

The study weaves together several prominent lines of evidence on the potential drivers of the condition, the ongoing presence of viral material, blood clotting and chronic inflammation, and offers up possible targets for clinical trials that can test treatments in humans.

"I'm impressed by the study," says Dr. Michelle Monje, a professor of neurology at Stanford University. "I think they did a beautiful job showing the causality of these changes."

Given that much of the work was done on mice, the implications for long COVID patients still need to be fully explored in future studies, but the results tell a "very nice linear story," says Akiko Iwasaki, an immunologist at Yale University.

Feel free to contact us with questions and/or comments.