Incidence trend and spatiotemporal distribution of brucellosis in western China, 2013−2021

Objective To analyze the incidence trend and spatial distribution of brucellosis in western China from 2013 to 2021 and provide data support and theoretical guidance for the development and effective implementation of brucellosis prevention and control strategies.

Methods Based on the incidence data of brucellosis in the western China from 2013 to 2021, Joinpoint regression analysis method was used to calculate the annual percent change (APC), and the long-term trend of brucellosis incidence was identified and tested. The spatial autocorrelation model was used to evaluate the spatial distribution pattern of the incidence of brucellosis in western China. Combined with cold and hot spot analysis and standard deviation ellipse, the spatial clustering characteristics of the incidence of brucellosis and the evolution of local spatiotemporal distribution patterns were further revealed. The potential factors affecting the incidence of brucellosis were explored by constructing an ordinary least squares (OLS) regression model.

Results During the observation period, the incidence trend of brucellosis in western China first increased from 2013 to 2014 (APC=48.32%, P<0.001), then decreased from 2015 to 2018 (APC=−7.96%, P=0.029), and increased rapidly again from 2019 to 2021 (APC=28.20%, P<0.001), with an average annual incidence of 6.11/100000. The spatial distribution characteristics showed that the global Moran's Index fluctuated between 0.38 and 0.53. The H-H clustering areas were mainly distributed in Ningxia and Xinjiang, the L-L clustering areas were mainly distributed in Tibet, Sichuan, Chongqing and others, the L-H clustering areas were mainly distributed in Qinghai, and there was no H-L clustering area. The provinces with spatial hot spots expanded from one to three, while Sichuan, Chongqing, Guizhou and others had cold spot or sub-cold spot areas for a long time. The standard deviation ellipse area decreased from 2006832.90km² in 2013 to 1668352.98 km² in 2021, the long axis shortened by 313.41 km, while the short axis increased by 47.94 km, the oblateness decreased by 0.81, and the azimuth angle decreased by 14.64°. The OLS regression results showed that the per capita green area (B=0.47), livestock breeding (B=0.38), and livestock flow (B=0.12) had a significant positive impact on the incidence of brucellosis, while the impact of meat production (B=−0.44) on the incidence of brucellosis was significantly negative in western China.

Conclusion The overall incidence of brucellosis was in increase in western China, with significant spatial clustering characteristics, and the overall spatial distribution range is shrinking. The distribution pattern has changed from vertical concentration to horizontal expansion. It is necessary pay close attention to the changes in incidence trend of brucellosis and strengthen case monitoring in high-risk areas and hot spots.