Spatiotemporal pattern of hand–foot–mouth disease in China: an analysis of empirical orthogonal functions

ObjectivesHand–foot–mouth disease (HFMD) is the most common infectious disease in China. Spatial and temporal patterns of HFMD in China provide valuable information on the relationship between HFMD and the geographical environment, and help in the prediction of HFMD transmission.Study designCross-sectional study.MethodsTotal HFMD morbidity per 10 days from May 2008 to March 2009 was recorded in 1966 counties in China. Empirical orthogonal function (EOF) analysis was used to obtain spatial and temporal patterns of HFMD.ResultsThe first five modes of HFMD morbidity explained 84.24% of the total variance. The dominant mode (first mode showing the highest variance) showed high HFMD morbidity in the western counties of Bohai Bay, the mid-south of China, the Yangtze River delta, the Pearl River delta and the areas bordering Vietnam from early May to late July 2008. The second mode showed high HFMD morbidity in the western counties of Bohai Bay, the north-east of China, north of Xinjiang and the Yangtze River delta from late May to the middle of August 2008. The third mode showed high HFMD morbidity in the Yangtze River delta, the Pearl River delta and the middle of the Huaihe River basin in early May 2008.ConclusionsEOF analysis of HFMD morbidity shows the main spatiotemporal patterns and can explain variance in HFMD in China.