Epidemiological analysis of human brucellosis in North Khorasan province, Iran (2018–2023): a six-year multicenter retrospective study

Brucellosis remains a significant zoonotic issue in Iran, especially in areas with substantial livestock agriculture. This study explores the epidemiological profile of human brucellosis in North Khorasan Province, northern Iran, over six years from 2018 to 2023. A retrospective analysis was performed on 24,104 suspected cases of human brucellosis reported to healthcare facilities in both urban and rural regions of North Khorasan. Cases were detected through clinical symptoms and validated via serological assays, including the standard tube agglutination test (SAT), the 2-mercaptoethanol (2ME) test, and the Combs Wright. Demographic characteristics, regional distribution, occupational exposure, animal contact, and the intake of unpasteurized dairy products were evaluated utilizing SPSS version 22. Chi-square testing identified relationships between variables, with significance established at p < 0.05. Of the total suspected cases, 1877 (7.7%) were confirmed positive for brucellosis. Incidence rates escalated over time, reaching a zenith in 2023. The most significant incidence of positive cases was observed in Shirvan (21.7%), followed by Faruj, Maneh, Samalqan, and Bojnurd. A majority of positive cases (81.1%) originated from rural areas, demonstrating a substantial correlation between infection and rural residency (p < 0.001). Livestock farming constituted the predominant occupation among infected persons (56.6%), with a higher prevalence in males than females (55.9% vs. 44.1%). The age cohort of 31 to 50 years exhibited the most significant infection rate at 39.1%. A substantial percentage of patients reported consuming unpasteurized dairy products (93.1%) and having direct interaction with animals (87.5%). Infection among family members was also significant (19.6%). Our results confirmed a considerable public health concern in North Khorasan, particularly affecting rural communities, livestock producers, and those who use unpasteurized dairy products. These findings highlight the necessity for focused control tactics, public awareness initiatives, and improved surveillance, especially in areas with high incidence rates.