Analysis of spatial-temporal distribution of influenza A (H1N1) pdm09 in Chengdu

Objective To understand the spatial-temporal distribution of influenza A (H1N1) pdm09 in Chengdu. Methods The spatial-temporal description and the spatial autocorrelation analysis were conducted by using the incidence data of influenza A(H1N1) pdm09 from May 9,2009 to December 31 in Chengdu collected from Infectious Disease Reporting Information System and related epidemiological investigations. Results The early A(H1N1) pdm09 cases were mainly imported ones, including the cases from the United States, Singapore and Australia, and the cases from Hong Kong, Guangdong and Shanghai. The incidence decreased gradually from the central urban area to the surrounding area, and the incidence in urban area accounted for 68.86%. There was a positive spatial autocorrelation of the incidence of A(H1N1) pdm09 in Chengdu (Moran's I=0.410,P=0.001). The high-high (H-H) areas were mainly distributed in six districts of urban area, including Qingyang (I=1.195,P=0.001), Jinjiang (I=0.773,P=0.003), Chenghua (I=0.495,P=0.026), Jinniu(I=0.658,P=0.004), High-tech Zone(I=0.842,P=0.001)and Wuhou(I=0.530,P=0.004), the low-high (L-H) area was Xindu(I=-0.650,P=0.029), located in the middle urban area. The differences in local spatial autocorrelation were not significant among the districts in central urban area of Chengdu. Conclusion The transmission risk of A(H1N1) pdm09 was higher in central urban districts than in middle urban area, and higher in middle urban area than in outer area. It is necessary to take targeted measures for the prevention and control of influenza A(H1N1) pdm09 in Chengdu.