Characterization of Clostridioides difficile in the U.S. Military, 2016-2024.

Abstract

Clostridioides difficile (C. difficile) is ubiquitous and remains a public health concern with substantial morbidity and economic burden. Active-duty service members (ADSMs) are a distinctive population given their younger age, frequent travel, antibiotic exposure, and close living conditions. This study updates the epidemiology of C. difficile infection (CDI) in ADSMs from 2016 to 2024. This retrospective analysis utilized data from 2.7 million ADSMs between January 2016 and December 2024 from the Medical Assessment and Readiness System. CDI was identified using ICD-10 codes. We extracted associated sociodemographic, occupational, and clinical variables, including age, sex, race/ethnicity, BMI, selected comorbidities, CDI treatment, and gastrointestinal diagnoses. A total of 2,489 CDI cases were identified, with an overall incidence rate of 21.4 per 100,000 person-years. Total annual infections declined from 324 in 2016 to 183 in 2024. Cases were concentrated in the Army (41.5%) and Air Force (28.0%). Women had a higher risk than men (risk ratio [RR], 1.7; 95% CI, 1.6-1.9). Risk increased with age, with ADSMs aged >50 at the highest risk (RR, 6.0; 95% CI, 4.6-7.9). Vancomycin was the most frequently recorded therapy, with lower use of metronidazole and fidaxomicin. In a large military cohort, CDI incidence was modest yet clinically relevant, with higher risk among women and heterogeneity across service branches. Compared with prior research, the overall incidence of CDI among ADSMs has increased, but over this observation window, the annual CDI incidence has declined by 43.5%. Gastrointestinal diagnoses, including irritable bowel syndrome and inflammatory bowel disease, were more frequently recorded among service members with CDI, including during follow-up after the index diagnosis. Findings support targeted prevention and follow-up, including outpatient antimicrobial stewardship and structured post-CDI care pathways.