16/11/2025
New study finds signs of COVID-19 still active in patients 3 years after infection.
A new study may have taken a major step toward explaining Long COVID by identifying lingering signs of the virus in the body years after the initial infection.
Researchers tracked 24 COVID-19 patients over nearly 900 days and used PET scans to observe the activity of T cells—key immune cells—throughout their bodies. Unlike in pre-pandemic control scans, the T cells in Long COVID patients showed up in unusual locations, including the lungs, gut, heart wall, spinal cord, and gastrointestinal tract. In several cases, researchers found actual COVID RNA in gut biopsies, suggesting that viral remnants—or even active virus—might persist in some tissues long after the original infection has ended.
While the study stops short of confirming whether these are active infections or lingering immune responses, its findings significantly bolster the theory that Long COVID may be caused by hidden virus reservoirs that the immune system never fully clears.
This would help explain why some patients continue to suffer from fatigue, brain fog, respiratory issues, and more—even years later. Experts say the discovery could finally direct research toward targeted treatments or therapies. “It should be seen as a significant step in advancing our understanding of this disease process,” said Professor Danny Altmann, who was not involved in the study but called it a vital development in tackling Long COVID.
paper
M. Peluseo et al. "Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection". Science Translational Medicine.
