| BackgroundGlobal climate change has had a significant impact on the ecological environment and human health.It is worth noting that climate change affects the prevalence of infectious diseases to a certain extent,leading to changes in the incidence,epidemic scope and situation of many infectious diseases,and having an influence on the population susceptibility to infectious diseases.Among them,extreme weather and climatic events are conducive to the survival and varnation of pathogenic microorganisms,thus increasing human exposure to pathogens.Higher temperature affects the survival and distribution of vectors and hosts,as well as human physiological functions and immune status,so as to change the epidemic characteristics of infectious diseases,expand the epidemic situation,and seriously threaten human health.Studies have shown that extreme precipitation and:flooding events along with meteorological factors are associated with the occurrence of intestinal infectious diseases.Rainfall provides a suitable environment for mosquitoes and other vector organisms to survive and reproduce,expanding their breeding areas.And it can also indirectly affect the spread and prevalence of infectious diseases by destroying infrastructure and environmental sanitation,or changing personal behavior habits.Temperature,humidity and other meteorological factors can have an effect on the spread and distribution of intestinal infectious diseases by affecting the reproduction and survival,transmission process and range of activities of bacteria and viruses.Infectious diarrheal,caused by bacteria,viruses,parasites and fungi,is a common intestinal infectious disease.Infectious diarrhea has a high incidence,with annual incidence of infectious diarrhea in China amounts to 800 million,and children under the age of 5 are high-risk groups.Previous studies mainly focused on the impact of heavy rainfall and flood events on infectious diarrhea,or concentrated on the relationship between diarrhea and extreme precipitation divided according to the percentile classification,while few studies were given concerning the impact of precipitation changes on diarrhea.There are many kinds of pathogens of infectious diarrhea,and the relationship between temperature and infectious diarrhea is mainly reflected in that bacterial diarrhea is occurring frequently in summer and viral diarrhea in winter,while there are few studies comparing the influence of temperature and threshold effect in different seasons.In China,other infectious diarrhea refers to infectious diarrhea other than cholera,dysentery,typhoid and paratyphoid,which belongs to category C infectious disease with high incidence.In this study,Beijing was taken as the research area.Based on the daily data of other infectious diarrhea from 2014 to 2016 and corresponding meteorological data,the effect of precipitation on diarrhea was quantitatively analyzed using the generalized additive model(GAM).And then distribution lag non-linear model(DLNM)was used to study the nonlinear relationship between average temperature and other infectious diarrhea and analyze the lag and threshold effects of temperature in warm and cold seasons.Stratified analysis was conducted on different genders,age groups,urban and rural population to identify the sensitive population,so as to provide theoretical basis for considering the influence of meteorological factors in the prevention and control of infectious diseases.Objective(1)Understanding the epidemiological characteristics of other infectious diarrhea in Beijing and its relationship with meteorological factors.(2)Examining the relationship between precipitation and other infectious diarrhea in different populations and lagged days.(3)Exploring the effect of average temperature on other infectious diarrhea,and analyzing the threshold effects of temperature in warm and cold season,that is,when the average temperature is above or below the threshold,the risk of disease for each 1? change in temperature.MethodsData of other infectious diarrhea form 2014 to 2016 of Beijing were obtained from the National Infectious Diseases Information System,the meteorological data of the same period were obtained from the China meteorological data sharing service network,and demographic information was obtained from the statistical yearbook of Beijing.Firstly,descriptive analysis was conducted in order to having a good learn of the conditions of meteorological factors and the distribution of diarrhea diseases in Beijing during the study period.Spearman correlation was used to analyze the correlation between diarrhea and meteorological factors,determining the meteorological variables included in the model.After controlling the confounding of temperature,humidity,seasonality and long-term trend by penalty spline function,the generalized additive model(GAM)was used to analyze the effect of every 10 mm change in precipitation on other infectious diarrhea and calculated the relative risk(RR)and 95%confidence interval(CI).Then the models were established for different populations to determine the sensitive population and the optimal lag period.The cross-basis of average temperature and lag days was established,and the relationship between temperature and diarrhea exposure was obtained by distributed lag non-linear model(DLNM)after controlling for the humidity,rainfall and long-term trend by natural cubic spline functions.The linear threshold function of DLNM was used to discuss the threshold of temperature on other infectious diarrhea in warm(May-September)and cold season(October-April).We also estimated the heat effect that average temperature exceeds the threshold and cold effect that average temperature below the threshold by examining the percentage of increased risk and its 95%CI when the temperature varied by 1 ?.Results(1)A total of 122 678 cases of other infectious diarrhea were reported in Beijing from 2014 to 2016.There were two peaks for the incidence of diarrhea from June to August in summer and November to January in winter,which basically coincided with the peak and valley of daily average temperature.In case composition,male cases were more than female cases;the age group of 0-4 years old had the largest number of cases,followed by the 15-39 year-old group;in tenns of occupational distribution,children were the main population for disease;for the regional distribution,suburban population accounted for the highest proportion,followed by urban-rural areas.From 2014 to 2016,the average annual incidence was 1.91‰,among which the incidence of male was higher than that of female and the highest incidence was 18.62‰ in the age group of 0-4 years old.(2)There was a linear relationship and lag effect between precipitation and other infectious diarrhea.The effect of every 10 mm increase in precipitation on the whole population was the greatest at the lag of 5 and 12 days,with RR values were 1.022(95%CI:1.009-1.035)and 1.022(95%CI:1.009-1.036),respectively.For female,the maximum effect occurred at the lag of 5 days,with RR=1.026(95%CI:1.013-1.039)for every 10 mm increase in precipitation;for urban population,the maximum effect was observed at the lag of 2 days(RR=1.030,95%CI:1.014-1.047),and at the lag of 12 days(RR=1.029,95%CI:1.015-1.044)for suburban population.(3)The exposure-response relationship of temperature and other infectious diarrhea was non-linear.Taking 0? as reference value,low temperature showed protective effect in the short term,harmful effect more than two weeks after the performance,while high temperature showed harmful effect(4)In warm season,when the average temperature exceeded the threshold,the rise of temperature(the heat effect)would increase the risk of diarrhea,showing harmful effect at the lag of 0 days.The greatest cumulative effect on the whole population appeared at the lag of 0-14 days,with each 1? increase in temperature exceeding the threshold(19?),the number of cases increasing by 7.163%(95%CI:6.423%-7.908%).Female and suburban populations were sensitive groups.For each I? increase in temperature above the threshold(19?),the cases increased by 7.640%(95%CI:6.798%-8.490%)and 7.250%(95%CI:6.334%-8.175%),respectively.(5)In cold season,the decrease of temperature lower than the cold threshold(the cold effect)would significantly increase the risk of diarrhea.The greatest cumulative effect appeared at the lag of 0-21 days:each 1? decrease in temperature below the threshold(-2?),the number of cases increased by 9.384%(95%CI:3.899%-15.158%).The cases increased by 2.552%(95%CI:0.628%-4.513%)for temperature exceeding the heat threshold(-14?).Female and suburban populations were sensitive groups.For each 1? decrease in temperature below the threshold(-3?),the number of cases increased by 12.484%(95%CI:4.773%-20.762%)and 12.537%(95%CI:4.661%-21.004%),respectively.Temperature exceeding the heat threshold mainly affected populations over 60 years old and in urban-rural areas,and had a protective effect for children under 5 years old.Conclusions(1)There were two peaks in the incidence of other infectious diarrhea in Beijing,which were from June to August and November to the next January.Children aged 0-4 years old had the highest incidence.(2)There was a linear relationship between precipitation and other infectious diarrhea in Beijing.Increased prec:ipitation would increase the risk of diarrhea with a lag of about two weeks,which had greater impact on female,urban and suburban populations.(3)When the average temperature in warm season exceeded 19?,the increase in temperature would increase the risk of other infectious diarrhea,and the heat effect occurred quickly and last for about two weeks.The cumulative heat effect was greatest for female and suburban populations.(4)For average temperature in cold season lower than-2?,the decrease in temperature would increase the risk of diarrhea disease.The cold effect last for around three weeks and was significant than heat effect in warm season.Female and suburban populations were sensitive groups. |
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