Epidemics and underlying factors of multiple-peak pattern on hand, foot and mouth disease inWenzhou, China

Background: Several outbreaks of severe hand-foot-mouth disease (HFMD) in East Asia and Southwest Asia in recent years have had a serious impact on the countries. However, the factors that contribute to annual multiple-peak pattern of HFMD outbreaks, and how and when do these factors play the decisive role in the HFMD transmission is still unclear.

Based on the surveillance data of HFMD between 1 January 2010 to 31 December 2015 in Wenzhou, China, the daily modelfree basic reproduction number and its annual average were first estimated by incorporating incubation and infection information, then the annual model-based basic reproduction number was computed by the proposed kinetic model, and finally the potential impact factors of multiple-peak pattern are assessed through the global and time-varying sensitivity analyses.

All annual model-based and model-free basic reproduction numbers were significantly higher than one. The school opening both in the spring and fall semester, meteorological e ect in the spring semester, and the interactions among them were strongly correlated with the annual model-based basic reproduction number, which were the main underlying factors on the annual multiple-peak pattern of HFMD outbreaks.

School opening was primarily responsible for peaks of HFMD outbreaks and meteorological factors in the spring semester should also be highly concerned. The optimum timing for social distance implementation is at the beginning of every school semester and health education focusing on personal hygiene and good sanitation should be highlighted in the spring semester.