[Spatial clustering and changing trend of hand-foot-mouth disease during 2008-2011 in China]

The purpose of this study was to explore the spatial clustering, specific clustering areas, as well as changing trend of clustering areas of hand-foot-mouth disease (HFMD).

Exploratory spatial data analysis (ESDA) was used to conduct spatial statistical analyses for the HFMD using 2008 - 2011 data at both provincial and county/district levels.

The Global Moran's I coefficients appeared to be 0.3336, 0.6074, 0.3372, 0.4620 and 0.4367 for 2008 - 2011 and for the combined 4 years, respectively. The corresponding P-values were 0.002, 0.001, 0.004, 0.001 and 0.001 respectively, when using the Monte Carlo tests with all the P-values less than 0.05. Moran's I coefficients ranged between 0.3 and 0.7, showing the appearance of moderate or higher clustering nature. Based on the results from nationwide analyses on clustering areas at the county/district levels between 2008 and 2011 (Moran's I = 0.5198, P = 0.001), it appeared a moderate clustering nature. When local autocorrelation analysis was applied at the provincial level, 3 hot spot areas in Beijing, Tianjin and Shanghai cities in 2008; 7 hot spot areas in Beijing, Tianjin, Hebei, Shanxi, Shanghai, Jiangsu and Shandong in 2009; four hot spot areas: Beijing, Tianjin, Guangdong and Guangxi; five hot spot areas: Fujian, Jiangxi, Hunan, Guangdong and Guangxi in 2011, were discovered. 390 hot-spot counties/districts were found through local autocorrelation analyses using the three-year data of 2008 to 2010.

Spatial clustering nature of HFMD incidence between 2008 and 2011 in China appeared to be moderate or high, with the clustered areas a north to south shifting trend. However, further investigation was in need to address this changing trend.