Spatial autocorrelation of human H7N9 avian influenza incidents in Zhejiang Province,2013-2014

Objective To investigate the spatial and temporal distribution of human H7N9 avian influenza cases in Zhejiang province during 2013-2014 and to provide evidences for prevention and control of the disease.Methods Data on reported human avian influenza incidents in Zhejiang province from January 2013 through December 2014 were collected from Infectious Disease Reporting System of Zhejiang Province and analyzed with ArcGIS 10.0 to describe spatial distribution and aggregation of the incidents.Results Totally 140 human H7N9 infections were reported and two incident peaks from March to May in 2013 and from January to February in 2014 were observed during the period in the province.Spatial autocorrelation analysis showed that the degree of the incidents aggregation in 2014 (I=0.51,Z=6.48,P<0.001) was stronger than in 2013 (I=0.27,Z=5.93,P<0.001);Getis-Ord statistics showed that the hotspots of the epidemics located mainly in north central area of Zhejiang province (Hangzhou city,Yuhang,Xiaoshan,Fuyang,Deqing,and HainingZ≥1.96) in 2013 and then expanded to Anji,Kecheng,Ningbo,Cixi,and Yuyao (Z ≥ 1.96) in 2014.Trend surface was established for the human avian H7N9 influenza incidents,showing that the incidence increased from east to central area then decreased from central area to the west and declined from north to south.Spatial autocorrelation analysis suggested that the number of incidents was correlated with population density and latitude (P<0.05);the prediction map for the epidemic generated by Co-Kriking method fits well with the actual incidents.Conclusion The spatial and temporal distribution of human H7N9 avian influenza incidents in Zhejiang province were highly clustered and the epidemics were severer from winter to spring in northern area.