VIENNA – People with pre-existing gastrointestinal issues who contract SARS-COV-2 may face a heightened risk of developing chronic fatigue associated with Long COVID, according to research from the Medical University of Vienna. The study highlights the potential role of gut health and inflammation within the microbiota in the long-term consequences of COVID-19.

The findings were published in the journal Allergy on May 15, 2025.

Pre-existing Gut Disorders Increase Long COVID Fatigue Risk

Researchers analyzed blood, saliva, and samples from 106 volunteers to understand the link between SARS-COV-2 infections and gastrointestinal symptoms. The participants included 30 individuals with chronic fatigue linked to Long COVID, 30 who had recovered from COVID-19 without lingering symptoms, 16 with chronic tiredness not related to Sars-Cov-2, and 30 healthy controls.

The study revealed that individuals with pre-existing gastrointestinal disorders who contracted coronavirus infection had a higher risk of developing post-COVID fatigue. The team also detected inflammatory markers in the intestinal microbiota of these patients. For instance, those with fatigue linked to Long COVID exhibited a higher LBP/SCD14 ratio and reduced IL-33 levels, “Which indicates altered immune activation and a weakened intestinal barrier”, according to the researchers’ press release. Additionally, their IL-6 levels, a marker of systemic inflammatory reactions, were elevated.

“Our results suggest that SARS-COV-2 infection can have long-term effects on the immune system and intestinal health…”

“Our results suggest that SARS-COV-2 infection can have long-term effects on the immune system and intestinal health, thus contributing to the development of post-viral fatigue syndrome”, adds Eva Untersmayr-Elsenhuber, co-director of the National Reference center for post-viral syndromes of the Medical University of Vienna.

Identifying Intestinal Inflammation Markers to Improve long COVID Treatment

The researchers believe that identifying the connection between gastrointestinal health and Long COVID could facilitate early identification of at-risk patients. “The identification of predictive markers of chronic fatigue syndrome linked to COVVI-19 could allow personalized prevention and treatment in the future”, explains Eva Untersmayr-Elsenhuber.

“What is particularly interesting is that the participants of our study were mainly young and healthy before the infection. In addition, COVVI-19 was generally benign, even asymptomatic. The difference resided in more frequent gastrointestinal disorders reported in the group that developed post-viral fatigue”, notes Johanna Rohrhofer, the study’s lead author.

The research team plans to continue their work to further validate these findings.