Spatial distribution characteristics and spatial autocorrelation analysis of human brucellosis in Shandong Province from 2014 to 2016

Objective To analyze the spatial distribution and spatial clustering of human brucellosis in Shandong Province from 2014 to 2016, and to provide scientific evidence for developing the targeted strategies and measures for the prevention and control of human brucellosis. Methods Based on GeoDA1.8.16 software, the global and local spatial autocorrelation analysis were used to analyze the data on human brucellosis in Shandong Province during the period of 2014-2016. Results A total of 10 630 brucellosis cases were reported during 2014-2016 in Shandong Province, and the incidence increased from 2.91/100 000(2 845 cases) to 4.03/100 000(4 009 cases),with the annual average incidence of 3.59/100 000,and showing an increasing trend on annual incidence (χ_ternd²=172.87, P<0.001).The epidemic range of human brucellosis distributed in 136 counties (cities or areas). The spatial autocorrelation analysis showed that Global Moran's I index for the incidence were 0.323, 0.300 and 0.179 respectively, and were all positive (all P<0.05), suggesting that there was a significant spatial clustering of human brucellosis during 2014-2016. Global Moran's I index decreased year by year (all P<0.05), suggesting decreased spatial clustering of human brucellosis during 2014-2016.The local autocorrelation analysis showed that high-high clustering areas were mainly distributed in the central and northern parts of Shandong, with consistent high morbidity. Counties or districts that located in the eastern coastal parts of Shandong presented the low-low relation. Conclusions The annual reported brucellosis incidence increased year by year in Shandong during 2014-2016, and the incidence of human brucellosis was non-randomly distributed. A positive spatial correlation and significant spatial clustering were found in the distribution of human brucellosis and the high-high clustered areas mainly distributed in the central and northern areas of Shandong, indicating that it is necessary to strengthen the prevention and control efforts in these areas.