Incidence and factors associated with fusobacterium infection: prospective from a population-based cohort study

Fusobacterium species infections present a diverse clinical burden, yet population-based data on their epidemiology and risk factors for bloodstream infection remain sparse. We aimed to characterize the clinical epidemiology of Fusobacterium and identify risk factors of bloodstream infection. A retrospective, population-level cohort study included all laboratory-confirmed Fusobacterium infections in Alberta, Canada (2012–2020). Data from centralized provincial laboratories were linked with administrative databases and supplemented by chart reviews. Multivariable logistic regression identified independent factors of bloodstream and species-specific infection. Among 298 patients (median age 52.5 years; 37.9% female), F. nucleatum (68.1%) and F. necrophorum (15.4%) predominated. The annual incidence was stable (0.61–1.03 per 100,000), peaking at 3.28 per 100,000 in those aged ≥ 80 years. Bloodstream infection occurred in 50.3% of cases and was independently associated with Charlson comorbidities (OR 4.80), substance use (OR 2.73), F. nucleatum (OR 2.65), and F. necrophorum (OR 16.39). Factors specifically associated with F. nucleatum (vs. other species including F. necrophorum ) included older age (OR 1.01), comorbidities (OR 2.51), and inpatient encounters (OR 2.33). Lemierre’s syndrome (5.7%) occurred primarily in younger patients (median age 18) with F. necrophorum . Fusobacterium infection burden varies significantly by species and age. F. nucleatum typically acts as an opportunistic pathogen in older, comorbid patients, whereas F. necrophorum remains a primary driver of high-acuity bloodstream infection in younger patients. Species-level identification and assessment of host factors, including substance use and weight of comorbidities, are essential for effective clinical risk stratification.