The Study Of The Impacts Of Floods On Water-borne Diseases In Zhengzhou City

[Background]Since the beginning of human civilization, floods have been paid attention greatly by people due to its serious impacts on society, economy, incidence and death. In recent years, due to the climate changing, the extreme precipitation events have frequently occurred. As a result, the frequency and intensity of floods due to the extreme precipitation events have dramatically increased. Annual disaster statistic report suggested that floods were the most frequent natural disaster in the world between 2001 and 2010.Due to the contaminated water source caused by floods, the contamination in the water source may lead to the incidence and transmission of water-borne diseases such as cholera, hepatitis A, bacillary dysentery, and typhus fever. Although some studies showed that floods could increase the incidence of water-borne diseases, the association between floods and water-borne diseases are far from clear. However, some studies found that there were no water-borne diseases outbreak and epidemics following the floods. China, as one of countries with most serious frequent natural disasters in the world, has suffered from serious floods from ancient times to the present. Zhengzhou, a city located in the plains in the middle and lower reaches of the Yellow River, has suffered from many floods. According to record of the yearbooks of meteorological disasters in China, there are 7 times floods occurring between 2005 and 2009 in Zhengzhou city.[Objective]Based on the 7 times floods occurring in Zhengzhou between 2005 and 2009, this study applied time series Poisson regression model to analyze the water-borne diseases incidence longitudinally, and to study the impacts of floods on water-borne diseases. This study mainly analyzed 4 aspects of objectives following:1. One of objectives in this study was to screen the sensitive water-borne diseases associated with floods from the database, which included the cholera, bacillary dysentery, typhus fever, paratyphoid and hepatitis A.2. This study aimed to estimate the possible lagged time of the association between floods and sensitive diseases.3. Floods events could significantly increase the risk of incidence of sensitive diseases. This study aimed to estimate the risk of floods on sensitive diseases, and calculate the relative risk values and their confidence intervals to assess quantitatively the impacts of floods on sensitive diseases.4. The impacts of floods among different population groups may be different, so that this study attempted to calculate the different disease burdens among different population groups.(Methods]Firstly, this study assumed the lagged time between 0 and 2 months, and compared the monthly morbidity of water-borne diseases between nonflooded and flooded months to screen and confirm the sensitive diseases associated with floods. Secondly, the month with the highest and significant correlation coefficient was confirmed the lagged period by applying the analysis spearman correlation to confirm the lagged time of between floods, meteorological factors and the monthly morbidity of sensitive diseases. In addition, after adjusting the lag effect and controlling the meteorological effect and seasonal effect, the time series Poisson regression model was applied to analyze the association between 7 times floods and sensitive diseases in Zhengzhou city from 2005 to 2009 to calculate the RR values of dysentery incidence among different gender groups and age groups. At last, the disease burdens of all the studied populations were compared by calculating the YLDs of different gender groups and age groups.[Results]1. Among the five water-borne diseases including the cholera, hepatitis A, typhus fever, paratyphoid and bacillary dysentery in this study, bacillary dysentery is the only disease associated with floods significantly during the lagged period. Other diseases are not correlated significantly with the floods during the lagged period. In addition, there is a lag effect between floods and bacillary dysentery morbidity, which is zero month lagged.2. Results of Poisson regression show that after adjusting the lag effect and controlling the secular trend, meteorological and seasonal effects, the coefficient of floods is a significant positive value, followed the significant negative coefficient of flood duration. The RRs of the whole population, male group, female group,0-14 age group,15-64 age group and above 65 age group are 2.80,3.13,2.53,2.75,3.03 and 2.48.3. Among the different gender groups, compared with female group, the YLD and attributed YLD of male group per 1000 people are 2.223 and 1.509 respectively, which are higher than female group with 1.513 and 0.913, respectively. Among the different age groups, the YLD and attributed YLD of 0-14 age group per 1000 people are the highest with 5.646 and 3.593, followed by 65 over age group with 1.474 and 0.880. The YLD and attributed YLD of 15-64 age group are the lowest among the age groups, with 0.952 and 0.638, respectively.[Conclusion]This study found that bacillary dysentery was significantly correlated with floods among the water-borne diseases among cholera, typhus fever, paratyphoid, hepatitis A and bacillary dysentery through the analysis between 7 times floods and water-borne diseases from 2005 to 2009 in Zhengzhou, which suggested that bacillary dysentery was the sensitive disease associated with floods. Floods, as a risk factor of bacillary dysentery occurrence, could significantly increase the incidence of bacillary dysentery. In addition, this study also found that flood duration was significantly associated with bacillary dysentery morbidity, and longer floods duration caused lower risk of bacillary dysentery.Among the different gender groups, compared with female group, the risk of male group on bacillary dysentery was higher during the flood period. Among the different age groups, the risk of 0-14 age group on bacillary dysentery was highest, followed by above 65 age group, and the risk of 15-64 age group was lowest. Consequently, the disease burden of male group was higher than male group among the gender groups, and the disease burden of 0-14 age group was highest among the age groups, followed by above 65 age group and 15-64 age group. Results would provide the significant implication to health promotion and education, and the reference for further research studying the impacts of floods on human health.