Even a mild case of COVID-19 or the flu can have lasting effects, but new research from Tulane University suggests the long-term impacts on the brain differ significantly between the two viruses. While both can cause lingering lung damage, COVID-19 is uniquely associated with persistent brain inflammation and injury to small blood vessels, even after the virus is no longer detectable in the body. These findings, published in Frontiers in Immunology, may help explain the prevalence of neurological symptoms like brain fog, fatigue, and mood changes in individuals experiencing long COVID.
The study, led by Dr. Xuebin Qin, professor of microbiology and immunology at the Tulane National Biomedical Research Center, highlights a critical gap in our understanding of the long-term consequences of respiratory viral infections. “Influenza and COVID-19 affect large populations worldwide and carry a significant public health toll, yet the mechanisms behind their long-term effects remain poorly understood,” Dr. Qin noted.
Lung Impacts: Similarities Between COVID-19 and Flu
Researchers utilized a mouse model to investigate the effects of both viruses, examining lung and brain tissue after the infection had cleared. In the lungs, both COVID-19 and influenza exhibited similar patterns of damage. Immune cells remained active longer than expected, and there was an increase in collagen, a protein associated with scarring. This collagen buildup can stiffen lung tissue, potentially contributing to the persistent shortness of breath reported by some individuals following a respiratory infection. The study authors noted that the repair response in the lungs was somewhat less pronounced after SARS-CoV-2 infection compared to influenza, but the overall lung pathology was broadly similar.
Distinct Brain Effects of COVID-19
The crucial distinction emerged when researchers examined the brain. While neither virus was detected within the brain tissue itself, mice infected with COVID-19 displayed signs of ongoing brain inflammation weeks after the initial infection. Importantly, they also exhibited evidence of small hemorrhages – tiny areas of bleeding – within the brain. These findings were not observed in mice infected with influenza.
Further analysis revealed disruptions in the signaling pathways regulating serotonin and dopamine, neurochemicals vital for mood, cognition, and energy levels. These disruptions were significantly more pronounced in the brains of mice infected with COVID-19 and were largely absent in those infected with influenza. Dysregulation of these pathways is strongly linked to the cognitive, emotional, and fatigue-related symptoms characteristic of long COVID, including the often-described “brain fog” and mood disturbances.
The study suggests that these vascular and immune changes within the brain following COVID-19 infection could be a key factor in the development of long COVID symptoms. The observed inflammation and small vessel injury may contribute to the neurological dysfunction experienced by some individuals long after the acute phase of the illness has passed.
Researchers emphasize the importance of understanding the underlying causes of these persistent symptoms to mitigate their long-term health consequences. “Face to the persistence of symptoms that complicate the recovery of some, it is essential to understand their causes in order to reduce the long-term consequences on health,” the researchers stated.
While this research was conducted in a mouse model, the findings provide valuable insights into the potential mechanisms driving long COVID and highlight the need for further investigation into the long-term neurological effects of SARS-CoV-2 infection. The differences observed between COVID-19 and influenza suggest that the long-term management and treatment strategies for these conditions may need to be tailored to address the unique pathological processes involved.
