Investigation and response data analysis on clustering of human brucellosis cases in Shaanxi province, 2020−2022

Objective  To analyze the epidemiological characteristics of 208 clustering of human brucellosis cases in Shaanxi province, and provide evidence for the prevention and control of human brucellosis.

Methods  Descriptive epidemiological methods was used to analyze the investigation and response data of 208 clustering of human brucellosis cases reported in Shaanxi from 2020 to 2022.

Results  A total of 208 clustering of brucellosis cases were reported, involving 596 individuals who were positive for brucella, in which 23 were identified as outbreaks later. The case clustering were mainly reported in July (17.31%), and reported in the 64 counties (56.67%) during this period. The male to femal ratio of the cases was 1.92:1, the cases reported in people aged 45−65 years accounted for the highest proportion (56.88%), and the majority of the cases were farmers (86.74%). The epidemics mainly occurred in cattle and sheep breeders (farms), accounting for 94.23%, which were mainly free range breeders (59.39%), followed by large-scale breeding farms (21.32%). The case relationship was mainly based on family members (77.88%). The time intervals between the onset, treatment, and diagnosis of cases were close to 90 days. The transmission routes of the epidemic were mainly through direct skin and mucous membrane contact and respiratory tract (72.11%). The infection sources of 118 cases could be traced. A total of 25586 livestock on hand were detected, in which 1534 were detected to be positive. A total of 6319 serum samples were collected from the people with exposure, in which 179 were positive. Environment disinfection was conducted for 33.65% of clustering of human brucellosis cases.

Conclusion The clustering of human brucellosis cases occurred widely in Shaanxi, sheep free range households were mainly affected, resulting in difficulty to trace and investigate the infection sources. Most cases were family members with low awareness of seeking medical treatment. So, it is necessary for disease control department at all levels animal husbandry departments in Shaanxi to carry out joint brucellosis epidemic investigation and reponse, strengthen the supervision of positive livestock, and pay attention to the improvement of clinical medical staff's brucellosis diagnosis and treatment level and professional population's awareness of seeking medical treatment.