Risk Factors for Brucellosis Relapse and Focal Complications: A Nine-Year Multicenter Study in an Endemic Region.

Objectives: Brucellosis remains a significant zoonotic disease in endemic regions, with relapse and focal complications posing significant clinical challenges. This study aimed to identify risk factors associated with brucellosis relapse and focal disease in North Khorasan, Iran, over a nine-year period.

Methods: A retrospective analysis was conducted on 2,568 confirmed brucellosis cases from 2015 to 2024, using data from multiple centers. Patients were diagnosed based on serological tests and categorized into relapse or focal brucellosis groups. Univariate and multivariate logistic regression models were used to analyze the demographic, clinical, and epidemiological variables.

Results: Relapse rates varied significantly by region. Of these, the relapse rate was 12.2% among patients with complications, compared to 9.5% in those without, not statistically significant, indicating that complications do not predict relapse. Predictors of relapse included older age, female sex, agricultural occupation, and specific Coombs-Wright titers (1/40 and 1/80). Focal complications (4.6%) most commonly involved arthritis (1.3%) and spondylitis (1%). Predictors of focal brucellosis included autumn onset, delayed diagnosis ≥3 months, hospitalization, and streptomycin use for 8-14 days.

Conclusions: Brucellosis relapse and focal disease are influenced by demographic, occupational, geographic, and treatment-related factors. These findings underscore the importance of early diagnosis and optimized antibiotic regimens in preventing complications.