Nikhil Prasad Fact checked by:Thailand Medical News Team Aug 24, 2026 54 minutes ago
Scientists investigating long COVID have identified a distinctive pattern of tiny gene-regulating molecules in the blood that may help explain why symptoms continue long after the initial coronavirus infection has ended.
Scientists found major differences in blood microRNAs that could provide new clues to the biological processes
driving persistent long COVID symptoms
The study examined microRNAs, or miRNAs, which are extremely small molecules that help control whether particular genes are switched up or down. Because these molecules can influence inflammation, immune activity, and other important biological processes, abnormal miRNA patterns could provide clues about long COVID.
Researchers Find 40 Important Differences
The research involved plasma samples from 10 people with post-COVID-19 syndrome and 10 people who had recovered from COVID-19 without persistent symptoms. The team analyzed 827 human miRNAs using highly sensitive molecular technology.
Researchers found 40 miRNAs that were significantly different between the groups. Of these, 36 showed increased levels in people with long COVID, while four showed decreased levels.
The differences were sufficiently distinct that the molecular profiles of the long COVID and recovered groups separated clearly in the study's analysis. However, some variation occurred among individual patients, potentially reflecting the complex nature of long COVID.
Shortness of breath affected eight of the 10 long COVID participants, while seven reported memory loss.
Several microRNAs Stand Out
Some changes were particularly large. miR-31-5p was approximately 9.8 times higher in the long COVID group, while miR-218-5p was about 42.7 times higher. miR-532-3p increased roughly 22.9-fold. Another molecule, miR-4458, was elevated about sixfold and was predicted to interact with 52 genes.
In this
Thailand Medical News report, these findings are important because miRNAs can regulate genes involved in inflammation and immune responses. The altered molecules were linked through computational analysis to biological pathways involving cell growth, cell adhesion, JAK-STAT signaling, and PI3K-Akt signaling.
miR-218-5p is especially interesting because previous research has connected it with regulation of inflammation in the nervous system, brain-cell communication, and processes associated with memory and sleep. This could make it relevant to neurological long COVID symptoms, although the current study cannot prove that the miRNA causes those problems.
Possible Clues to Persistent Inflammation
Researchers also found reduced levels of miR-449a. This molecule can influence cell-cycle regulation and genes involved in inflammatory signaling. Overall, the results suggest that long COVID may involve an imbalance between inflammatory activity and mechanisms normally responsible for regulating immune responses.
The institutions involved were São Paulo State University (UNESP), inc
luding the Botucatu School of Medicine, School of Veterinary Medicine and Animal Science, and Institute of Biosciences of Botucatu in Brazil, together with Vanderbilt University Medical Center in the United States.
Conclusions
The findings provide intriguing molecular evidence that people with long COVID may carry a recognizable blood miRNA signature involving inflammation, immunity, cell signaling, and neurological processes. However, with only 20 participants, much larger studies are required before these molecules can be considered reliable diagnostic biomarkers or treatment targets.
The study findings were published as a medRxiv preprint and have not yet been peer reviewed.
https://www.medrxiv.org/content/10.64898/2026.08.16.26359035v1
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https://www.thailandmedical.news/articles/long-covid
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