If you’ve felt the effects of influenza or COVID-19 weeks or even months after infection, you’re not alone. Doctors are seeing long-lasting impact and damage from these infections. Now, a new study from Tulane University sheds light on the specific biological changes, which may help develop treatments aimed at preventing lasting damage.
Overall, the researchers found that while both viruses can leave lasting lung damage, only SARS-CoV-2 infection caused persistent brain inflammation and small blood vessel injury, even after the virus was no longer detectable.
The findings, published in Frontiers in Immunology, help explain why long COVID often includes neurological symptoms such as brain fog, fatigue and mood changes, while influenza is more commonly associated with respiratory complications.
To separate effects common to severe respiratory infections from those unique to COVID-19, researchers used a mouse model to examine lung and brain tissue after infection had cleared.
In the lungs, both viruses left behind a similar picture: immune cells that failed to fully stand down and increased buildup of collagen. Those changes can stiffen lung tissue and make breathing feel more labored.
But when the researchers looked more closely, they found a key difference. After the flu, the lungs appeared to switch into repair mode, sending specialized cells into damaged areas to help rebuild the lining of the airways. That repair response was largely missing after COVID-19 infection, suggesting the virus may interfere with the lung’s natural healing process.
The most striking differences, however, appeared in the brain. Although neither virus was found in brain tissue, mice that had COVID-19 showed signs of persistent brain inflammation weeks later, along with tiny areas of bleeding. Gene expression analysis revealed ongoing inflammatory signaling and disruption of pathways involved in serotonin and dopamine regulation, systems closely tied to mood, cognition and energy levels. These persistent changes were largely absent in influenza-infected animals.
As lingering symptoms continue to complicate recovery for some, understanding what is driving them is essential to reducing long-term health consequences.
Data from Tulane University