Spatio-temporal analysis of human brucellosis in North Khorasan, Iran (2015-2023): A cross-sectional study

The present cross-sectional study was conducted to study the epidemiological and spatio-temporal dynamics of human brucellosis in North Khorasan province, Iran, from 2015 to 2023. All the spatial analyses were performed using ArcGIS 10.8.2. A total of 2855 confirmed cases were reported during a nine-year period, of which 56.39% were male and 71.14% were rural residents. The highest number of cases was observed in 2023, and the lowest number in 2018. Median age of patients was 41. Most affected individuals were livestock farmers or household members involved in animal husbandry, and 86.67% reported consumption of unpasteurized dairy products, and 82.25% reported close contact with livestock. Logistic regression analysis revealed that rural residents had significantly higher odds of dairy consumption (OR = 2.54; 95% CI: 1.91-3.36) and livestock interaction (OR = 8.93; 95% CI: 6.77-11.83) than urban residents. A familial history of brucellosis correlated with an increased risk of cattle exposure (OR = 2.13; 95% CI: 1.40-3.33). Spatial analysis of Global and Local Moran's I indicated substantial clustering of incidence throughout the province. Bojnord, Shirvan, and Faruj were persistent high-incidence clusters from 2016 to 2023, and they can be considered important stable hotspots. LISA cluster maps also confirmed Shirvan and Faruj as persistent high-high clusters, suggesting prolonged localized transmission for several years. Other counties showed intermittent patterns which may reflect heterogeneity, possibly attributable to local exposure conditions or gaps in surveillance. No statistically significant low-low clusters were found. The study shows there are marked regional differences in brucellosis incidence, strongly correlated to rural residence, livestock contact and consumption of unpasteurized dairy products. The persistence of hotspots underlines the relevance of region-specific surveillance, vaccination campaigns and community-based strategies to reduce transmission in high-risk regions.