PARIS – A French research team has identified a unique viral signature in the blood of Crohn’s disease patients, potentially offering a less invasive alternative to current diagnostic methods like colonoscopies. the study, published December 31, 2025, challenges the long-held belief that blood is sterile and highlights the presence of a distinct “blood virome” markedly different between those with and without the inflammatory bowel disease. This breakthrough could lead to faster, more accessible diagnoses for the nearly 150,000 people in France living with Crohn’s, and potentially for the estimated 1.4 million americans affected by IBD.
A new study offers a potential breakthrough in the diagnosis of Crohn’s disease, a chronic inflammatory bowel disease (IBD) affecting nearly 150,000 people in France. The research, published December 31, 2025, identifies a unique viral signature in the blood of individuals with Crohn’s, paving the way for less invasive diagnostic tests. Crohn’s disease can significantly impact quality of life, and earlier, more accurate diagnoses are crucial for effective management.
For years, diagnosis has relied heavily on endoscopy with biopsies, a procedure considered invasive. While alterations in gut bacteria are well-established in Crohn’s disease, the role of viruses in the body – specifically the fecal virome – has remained largely unexplored as a potential biomarker.
Existence of Blood Virome Confirmed
Researchers have long believed that blood was sterile, but this collaborative French study, involving the National Institute for Agricultural, Food and Environmental Research (Inrae), Sorbonne University, and Paris Public Hospital System (AP-HP), proves otherwise. Analysis of plasma samples revealed the presence of 17,454 viral taxonomic operational units (vOTUs). The majority of these viruses are bacteriophages – viruses that target bacteria.
While the viral load in plasma remains relatively low and stable – around 100,000 particles per milliliter – it contrasts sharply with the much higher concentration found in stool samples, approximately 1 billion viruses per gram. The discovery of a consistent virome in blood opens new avenues for understanding systemic inflammation and disease processes.
Specific Phages May Hold the Key to Crohn’s Diagnosis
The study found that individuals with Crohn’s disease had a distinct virome profile in their blood, enriched with phages that target intestinal bacteria (anti-Bacteroidota). This suggests an increased transfer of these viruses from the gut, potentially due to the compromised intestinal barrier characteristic of the disease. In contrast, healthy individuals primarily exhibited phages associated with bacteria commonly found in the bloodstream (anti-Acinetobacter).
This qualitative difference in viral signatures allows for a clear distinction between patients and healthy controls, a feat previously unattainable with the highly variable fecal virome. The ability to differentiate Crohn’s patients based on blood samples could revolutionize diagnostic approaches.
Clinical Implications
These findings position the blood virome as a promising biomarker for Crohn’s disease, potentially leading to the development of rapid blood tests for diagnosis, treatment monitoring, and assessment of treatment response. Rapid blood tests are often preferred by patients and can streamline healthcare processes.
Researchers emphasize that larger studies are needed to validate these findings and determine the clinical value of the blood virome in Crohn’s disease and other inflammatory bowel diseases.
