These differences may be explain the different relative risks between the two cities. A study found that as the rapid process of urbanization in Kaifeng, the land structure was changed with increased impervious surface and reducing land area as a result of more concrete structures built on the ground.44 Moreover, the old drainage system was unscientific and in bad repair, leading to the poor capacity of sewer drainage. During the period of heavy precipitation, flooding is more likely to occur in Kaifeng and floodwater could easily be infected with pathogens through cross-contamination due to infiltration and inflow between sewage and water pipes. In addition, the economic strength of

Kaifeng is the worst compared with Bafilomycin A1 chemical structure Zhengzhou and Xinxiang,45 which means that CYC202 the financial input is little to the public health and health care. Thus, the relative risk

on dysentery after flood was the highest among the three cities. This study has also indicated that the risk of dysentery after floods in the whole area may not be severe relatively. With the reference of Kaifeng city, Zhengzhou and Xinxiang had a higher intensity of dysentery epidemics after floods. It may be because that the density and mobility of population influence greatly on the transmission of dysentery between people, which is the largest in Zhengzhou as the capital of Henan Province, followed by Xinxiang due to the second level of population density and mobility among the study cities. Moreover, the reason for this difference may

be that the local environment of Zhengzhou and Xinxiang were more suitable for the survival and reproduce of the dysentery pathogens compared with Kaifeng. The results of the multivariate models demonstrate the quantified impact of flood duration on dysentery, indicating a negatively correlation between flood duration and the morbidity of dysentery. The risk of dysentery Ribose-5-phosphate isomerase could be higher after a sudden and severe flooding than that after a prolonged and moderate flooding. During the sudden and severe flooding, heavy precipitation was strongly destructive for human and health infrastructure, which may cause serious floodwater contamination. In this case, more people would be contact with floodwater, resulting in a greater likelihood of being infected with dysentery. However, during a prolonged and moderate flooding, the transmission and infection of dysentery pathogens may be decreased due to lower destruction and contamination. Research examining the effect of flood on infectious diseases on a basis of retrospective data collection had methodological shortcomings with a lack of longitudinal analysis.46 In our study, we used a time-series data from 2004 to 2009 to analyze the effects of many times floods on the onset of dysentery. It provides clear evidence of the relative risk on dysentery after floods.