Global gut microbiome atlas identifies epidemiologic-stage-specific signatures in inflammatory bowel disease.

The global rise of inflammatory bowel disease (IBD) reflects environmental shifts, yet how these changes are embedded in the gut microbial ecology remains unclear. We construct a microbiome atlas comprising 245,627 profiles. By classifying countries into three epidemiologic stages, we establish a framework. As the IBD burden increases, the gut microbial alpha diversity declines, and community structures form distinct clusters. This transition is characterized by a gradient of core genera. Integrating six shotgun metagenomic cohorts, we identify the depletion of anabolic pathways in IBD patients. Strain-level analysis reveals that epidemiologic staging shapes genetic architecture within species, identifying an IBD-enriched subclade of Eisenbergiella associated with elevated fecal cholic acid. We develop a microbial inflammatory risk score (MIRS), based on 19 genera, that discriminates IBD from controls (area under the curve [AUC] = 0.92). MIRS correlates with IBD prevalence. Our study provides an atlas linking epidemiology to microbiome ecology and strain evolution, offering a foundation for population-level surveillance and interventions in IBD.