Epidemiological characteristics of human brucellosis in Jiande City from 2005 to 2024

Objective: To investigate the epidemiological characteristics of human brucellosis in Jiande City, Zhejiang Province from 2005 to 2024, so as to provide the evidence for strengthening the prevention and control of brucellosis. Methods: Data on brucellosis cases and surveillance in Jiande City from 2005 to 2024 were collected through the Chinese Disease Prevention and Control Information System, the annual brucellosis surveillance reports from the Jiande Center for Disease Control and Prevention, and the annual summaries of brucellosis prevention and control efforts. The epidemiological characteristics of human brucellosis were analyzed using a descriptive epidemiological method. Results: A total of 1 125 individuals were monitored in Jiande City from 2005 to 2024, with 18 seropositive cases identified and the seropositivity rate of 1.60%. The average annual seropositivity rate from 2015 to 2024 was 3.35%, which was significantly higher than that of 0.57% from 2005 to 2014 (P<0.05). There were 10 confirmed brucellosis cases and 8 asymptomatic infections, with no reported deaths. The peak incidence occurred between March and August. Among the 16 towns (streets) in Jiande City, 8 reported brucellosis cases. Of the brucellosis cases, 14 were male and 4 were female, with a male-to-female ratio of 3.5∶1. The majority of cases (13 cases) were aged between 40 and 60 years. Occupational exposure was identified in 16 cases, all of whom were infected through direct hand contact with the excreta, secretions, or animal products of infected sheep or cattle. The primary source of infection was sheep, followed by cattle. Five strains of Brucella were isolated and cultured, all identified as Brucella melitensis biovar 3. Conclusions: The brucellosis epidemic in Jiande City remained at a sporadic and low prevalence level from 2005 to 2024, with an increasing trend observed from 2015 to 2024. Male occupational groups aged 40 to 60 years were the key population for brucellosis prevention and control, and sheep were the primary source of infection.