Project And Evaluation Of The Burden Of Infectious Diarrhea Attributed To Floods

BackgroundAs global warming intensifies, the intensity and frequency of extreme weather events may increase in some areas under climate change. Studies have shown that the extreme precipitation tend to increase in the next 50 years in China. Flood is the most common natural disasters. China is one of the countries which suffer from floods severely. Floods has a tendency to increase in recent years. The special topography and climate condition make floods happen frequently in Hunan and Guangxi Province.Infectious diarrhea, as an intestinal infectious disease, was caused by bacteria, viruses and other pathogens. It is still an important public health problem worldwide. About 2.5 million children die each year due to diarrhea in developing country. The incidence of infectious diarrhea in our country is usually high, and diarrhea disease count for nearly a quarter of the 39 kinds of statutory reporting infectious disease. The incidence of infectious diarrhea is also high in Guangxi and Hunan Province.Effect of floods on public health can be divided into the short-term effect and long-term effect, the short-term effects include injury, death, water-borne diseases and vector-borne diseases; the long-term effects include non-communicable diseases, mental illness, malnutrition and birth defects, etc. Studies found that the relationship between diarrhea diseases and flood is close but still not clear due to lack of intensive study. In-depth research about the relationship between diarrhea diseases and flood is rare, and studies about attributable burden and project the excessive cases of infectious diarrhea have not been reported in literature.Objectives(1) The study aimed to assess the lag effect of flood on infectious diarrhea.(2) The study aimed to evaluate the attributable burden of infectious diarrhea due to flood.(3) The study aimed to project the excessive incidence of infectious diarrhea due to flood in the future period.MethodsNanning city in Guangxi, Huaihua city in Hunan Province was chosen as our study area. Data about infectious diseases was obtained from the National Notifiable Disease Surveillance System. Flood data and meteorological data was obtained from the Yearbook of meteorological disasters and the China Meteorological Data Sharing Service System. Population data was obtained from the center of scientific data on public health.Assessment the attributable burden of infectious diarrhea due to flood: Generalized additive models based on time series data was used to analyze the lag effects of flood on infectious diarrhea, then the relative risk and confidence interval was obtained from the model; The potential impact fractions was calculated based on the relative risk. The attributable burden of infectious diarrhea was assessed according to the Comparative Risk Assessment framework recommended by World Health Organization.Project the excessive incidence of infectious diarrhea due to flood in the future period:The distributed lag non-linear model was used to evaluate the relationship between floods and infectious diarrhea, then the relative risk at different lag was obtained from the distributed lag non-linear model; The occurrence of flood in the future was projected according to the meteorological data in the future period; The excessive incidence of infectious diarrhea due to flood in the future period under different scenarios was lastly projected according to the effect of flood on infectious diarrhea, future population, future occurrence of flood and the future change of temperature.Results(1) Result from the generalized additive model shows that the value of relative risk for flood on the risk of infectious diarrhea was 1.241 (95% CI:1.029-1.497), while each day increase for the flood duration, the incidence of infectious diarrhea will increase by 4.8%(95%CI:2%-7.6%), and the maximal effect of flood was observed at flood month.(2) The potential impact fractions of flood was 0.194, the average attributable burden per 1000 of infectious diarrhea was 0.00012 people years, age groups with the highest average attributable burden was 0～4 years old age group, followed by the 5～14 years old age group, and men over the age of 80.(3) Result from the distributed lag non-linear model shows the value of relative risk for flood on the risk of infectious diarrhea was 1.149 (95% CI:1.003～1.315), the value of relative risk for average temperature on the risk of infectious diarrhea was 1.023 (95% CI:1.003～1.044), the best lag periods for them were both at lag 1 week.(4) Results shows that while considering the floods and temperature at the same time, the projected number of infectious diarrhea cases in 2100 in Huaihua was 2195 (2031～2309),2031 (2103～2450) respectively under the RCP 4.5, RCP 8.5 scenario, which is increased by 5.6% and 5.6% respectively than the benchmark year.Conclusions(1) Flood can increase the risk of infectious diarrhea, and its harmful effect will reach the maximum at lag 1 week after the flood. The longer the duration of the flood lasted, the higher the incidence will be.(2) The burden of infectious diarrhea due to flood has a downward trend year by year, vulnerable populations such as children and the elderly should be paid more attention.(3) The incidence of infectious diarrhea in the future period is likely to increase due to floods and temperature changes, which suggest that long-term planning should be developed to avoid potential risks of infectious diarrhea after floods.