| BackgroundMumps is an acute respiratory infectious disease caused by mumps virus.It can cause serious complications such as deafness and encephalitis,resulting in serious disease burden.Although immunization can be obtained by vaccination,the prevalence of mumps still shows an obvious seasonal trend under the condition of high vaccination rate.Meteorological factors have been proved to have a significant correlation with this seasonal prevalence.In recent years,climate change continues,and the problem of global warming has not been effectively solved.The frequent occurrence of extreme weather has not only affected daily life,but also affected the spread of many infectious diseases,which has done great harm to people’s health.Therefore,it is of great public health significance to consider the influence of meteorological factors on mumps in disease prevention and control.A large number of literatures have been reviewed and it is found that the studies on the effects of meteorological factors on infectious diseases are mainly divided into two categories.One is to directly construct the relationship between meteorological factors and the number of cases and conduct quantitative analysis;the other is theoretical research which mainly uses the dynamic model to explore the transmission mechanism of infectious diseases.The former is flexible,adjustable and easy to operate.It is often used to analyze the risk of meteorological factors on the incidence of infectious diseases.At present,most related studies use this method,but usually conducted on only a specific region or adopted a single statistical model,which may ignore the difference of the effect of meteorological factors on the incidence of mumps between different cities and the interaction of meteorological factors on the incidence of mumps.For the dynamic model of infectious diseases,the current dynamic model mainly aimed at natural foci diseases with animal vectors such as dengue fever.There are relatively few studies on infectious diseases such as mumps.The study of mumps using dynamic model rarely includes meteorological factors or considers the impact of age structure.Therefore,the analysis is often not comprehensive enough and it is difficult to get more in-depth research results.In addition,after getting the impact of meteorological factors on the incidence of mumps,most of these studies often do not perform further analysis on the mumps incidence risk differences between different cities or regions or the early prediction of mumps incidence.Therefore,the regional risk assessment cannot be carried out comprehensively,and it is difficult to achieve accurate prevention and control of mumps.Therefore,based on the epidemic data of mumps in Shandong Province,this study first described the epidemiological characteristics of mumps,and then made a comprehensive and systematic analysis of the effects between meteorological factors and the incidence of mumps in all regions or cities of Shandong Province to explore the sources of differences in effects between different cities and cities,and to identify vulnerable subgroups.Secondly,through the construction of a dynamic model with age structure and meteorological factors,the role of meteorological factors in the transmission mechanism of mumps is analyzed.Finally,the regional risk assessment was carried out for 17 cities in Shandong Province,and the prediction and early warning are carried out for the cities with high incidence and high risk of mumps,so as to achieve its accurate prevention and control.This study systematically analyzed the epidemiological characteristics of mumps,the relationship between meteorological factors and the incidence of mumps in Shandong Province,identified vulnerable people and carried out regional risk assessment,prediction and early warning.The results of the study can help local government departments and relevant prevention and control agencies to deal with adverse weather in advance,take precautions,and provide scientific theoretical basis and decision support for early prevention of mumps,reducing the spread of diseases and reducing the risk of disease.The accurate prevention and control of convective gills can also provide reference theoretical methods and technical support for the prevention and control of other respiratory infectious diseases.Materials and methods1.Data collection and collationThe mumps case data of Shandong Province from 2009 to 2017 are collected from the information system of the Shandong Center for Disease Control and prevention.The meteorological data from 2009 to 2017 are collected from China Meteorological science data sharing service system.The social,economic and demographic data of the same period are collected from the statistical yearbook of Shandong Provincial Bureau of statistics from 2009 to 2017.All data are subject to quality control by relevant departments and professionals.The data are cleaned according to the research needs and sorted into data sets according to different time scales.2.Statistical methods(1)Describe the epidemiological characteristics of mumps in time,space and population in Shandong Province from 2009 to 2017.(2)The effect analysis of meteorological variables on the incidence of mumps.Firstly,the differentiation and factor detectors in the geographical detector were used to preliminarily detect the meteorological factors that have a great impact on the incidence of mumps in different regions of Shandong Province,and then these variables were analyzed in 17 cities by using the distributed nonlinear lag model,and the merger effect of urban level is obtained through metaanalysis to explore whether economic,population and other factors affect the heterogeneity of effects among different cities;Secondly,the interaction detector was used to detect the variables with the largest interaction between meteorological factors and mumps incidence in each meteorological area.These variables were selected and the penalty spline of generalized additive model was used to obtain the binary response surface,so as to further analyze the similarities and differences of the interaction between meteorological factors and mumps incidence in different regions.At the same time,the comprehensive index was used to replace the interaction,and the distributed nonlinear lag model was used to explore the influence of meteorological factors,their interaction and time lag on the incidence of gill;Finally,according to all the above analysis,the potentially vulnerable population under different meteorological factors or comprehensive indicators of meteorological factors was identified.(3)It is assumed that meteorological factors affect the seasonal epidemic of mumps by affecting the infectious power of mumps virus.Based on the age structure,the SVEIR infectious disease dynamics model was constructed,which divides the population into five categories:Susceptible(S),Vaccinated(V),Exposed(E),Infections(I)and Removed(R).The principal components of meteorological factors were calculated and the first two principal components were adopted in the following analysis.It is assumed that meteorological factors affect the seasonal epidemic of mumps by affecting the infectivity of mumps virus.The principal components of meteorological factors were included in the infectivity function.The estimated values and confidence intervals of key parameters were obtained by iterative filtering method,and then the interpretation degree of meteorological factors in the transmission mechanism of mumps was obtained.(4)Attribution risk,effective reproductive number and comprehensive risk assessment framework were used respectively to assess the risk of mumps caused by meteorological factors in 17 cities of Shandong Province.Based on the distributed lag nonlinear model,the attribution risk of temperature-induced mumps in Shandong province was calculated from a backward perspective,and the transmission capacity of 17 prefectures and cities in Shandong province was estimated by using the calculation method of effective reproduction number based on Poisson process.Using the comprehensive risk assessment framework based on population exposure,risk,sensitivity and vulnerability,we assessed the comprehensive risk of mumps caused by meteorological factors in various prefectures and cities of Shandong Province.(5)Three models including generalized additive model(GAM),random forest(RF)and support vector machine(SVM)were used to predict the incidence of mumps in Shandong province by using meteorological factors.The fit of goodness of the model were evaluated by R2 and root mean square error,and the sensitivity,specificity and AUC were used to evaluate the prediction ability of the early warning models.The moving percentile method was used to change the early warning threshold for sensitivity analysis,and the best early prediction model and respective threshold were selected.Results1.The incidence of mumps in Shandong Province and cities represented obvious characteristics of population,time and space distribution.The prevalence of mumps in Shandong Province shows an overall trend from steady state to rising first and then decreasing.From 2009 to 2017,men accounted for 61.27%～69.82%of the total incidence of mumps in cities all over Shandong Province.The number of male cases was higher than that of women.The high incidence age groups of the population were 5～14 years old.A Students,nursery children and scattered children accounted for 87.83%of the total cases.The seasonal epidemic characteristics of mumps in 17 cities were two peaks:spring summer peak and winter peak from April to July and December to January(the next year).The winter peak is obvious among students but not among children.The spatial distribution of the incidence of high incidence age group in various districts and counties of Shandong Province shows that the incidence in the western region is higher than that in the eastern region.2.The effect analysis of meteorological factors on the incidence of mumps shows that there is an obvious nonlinear correlation between each meteorological factor and the number of mumps,and the incidence risk of mumps caused by meteorological factors is different in different regions and cities.The daily average temperature has the greatest impact on the incidence of mumps,followed by sunshine hours,daily average relative humidity and wind speed.Taking the median 14.7℃ as the reference,when the lag time is 25 days,the combined effect of low temperature on the incidence of mumps in cities all over Shandong Province shows a dangerous effect,and the risk is the highest when the temperature is-12.6℃(RR=1.871,95%Cl:1.182～2.961).Lower per capita GDP,lower urban population proportion,higher population density and higher birth population have higher risk of mumps at low temperature,but the main source of combined effect heterogeneity is the proportion of primary and secondary school students.High temperature has different effects on different cities.It shows a dangerous effect on some cities,but it shows a protective effect on other cities and has no statistical significance;Different regions are affected by the interaction of different meteorological factors,but it is mainly composed of temperature,humidity,wind speed and sunshine hours.Compared with other regions,the incidence risk in Northwest and central Shandong is higher,but the binary response surface of interaction is similar to that in other regions;The interaction between meteorological factors and parotid disease in the peninsula is the most different from that in other regions,and the daily average precipitation is only meaningful in the peninsula;The main vulnerable groups identified by the combined effect of low temperature,low temperature humidity index and low wind cold index in Shandong Province are men,11-14-year-old age group,nursery children,scattered children and all male adolescents.3.Using the constructed SVEIR dynamic model,the infectivity,incubation period,infection period and other epidemiological parameters of mumps were estimated.It was found that the prevalence of mumps was not only related to the contact rate between different age groups,but also affected by meteorological factors.The fitting results of the model show that the number of cases in Jining City shows a gradual upward trend,in which the number of cases in the age groups of 5～9 and 10～14 is more,which is basically consistent with the trend of the number of reported cases of mumps in Jining City from 2009 to 2013.The average incubation period of mumps in Jining City is about 2.488 weeks(95%CI:1.818～3.300),and the average infection period is about 2.688 weeks(95%CI:2.513～3.039).The best fitting model is the model when meteorological factors lag for 3 weeks,with a goodness of fit of 0.726 and root mean square error of 8.020.Overall,the model is not very sensitive to the lag weeks of meteorological factors,and the explanation degree of meteorological factors to the seasonal epidemic trend of mumps in Jining City from 2009 to 2013 is 36.39%.4.Temperature has a significant difference in the risk of mumps in different cities of Shandong Province.The number of cases of mumps in Shandong Province due to daily average temperature exposure accounted for 9.93%of the total number of cases.The cities with higher attribution risk caused by low temperature are mainly distributed in central and southern Shandong.Low temperature has the greatest impact on Zibo City,which can be attributed to 18.07%of the total cases in Zibo City.Heze City,where the attribution risk of high temperature caused mumps population is the lowest,accounts for 12.37%of the total cases.The effective regeneration number of mumps in different prefectures and cities of Shandong Province during the period of one dose vaccination was 1.016～1.218,and the median was 1.046.After two doses of vaccination,the effective reproduction number decreased to 1.004～1.046,and the median was 1.014.In the framework of comprehensive risk assessment,the exposure degree of central and southwestern Shandong is higher,the sensitivity of southwestern and southern Shandong is higher,and the adaptability of central Shandong and peninsula is higher.The comprehensive risk caused by cold wave in the southern and central regions of Shandong Province is relatively high,and the comprehensive risk caused by heat wave in southwest and northwest regions is relatively high.The cities with higher comprehensive risk caused by low temperature and extremely low temperature are Liaocheng,Linyi,Zaozhuang and so on.5.Through the prediction and early warning of the cities with high incidence and high risk,it is found that the generalized additive model has a better effect than random forest and support vector machine.The results of the generalized additive model showed that in ordinary years(stationary trend)and high incidence years(rising trend),the R2 of Qingdao test set is the highest,the sensitivity is more than 0.857,and the area under ROC curve(Areas under the curve,AUC)reaches 0.941 and 0.977.R2 of the test set in Zaozhuang City is lower when predicting high incidence years,but the highest in ordinary years,and the sensitivity in both cases were 1,while AUC was above 0.972.In the sensitivity analysis of the early warning threshold,except for the early warning of the high incidence years in Zaozhuang City,the sensitivity of the generalized additive model is 1.In all cases,the AUC is more than 0.939,which can accurately capture the epidemic trend of mumps.Conclusions1.The epidemic of mumps in Shandong Province showed obvious seasonality,with two peaks every year,and the high incidence age groups were 5-9-year-old and 10-14-year-old age groups.The annual increase percentage of the number of cases in the 0-4 age group was significantly lower than that in other age groups,and the difference of epidemic peak value in different seasons was the main reason why Shandong Province was divided into two epidemiological regions.2.There are obvious regional differences in the influence of meteorological factors on the incidence of mumps in different climatic regions and cities,and the most influential meteorological factor is temperature.Low temperature has the greatest impact on prefectures and cities in Shandong Province,and the proportion of primary and secondary school students has a modification effect on it.Temperature,relative humidity,wind speed,sunshine hours and their interaction have the greatest influence on the incidence of mumps in the northwest of Shandong Province.Male,11-14 age group,preschool children and scattered children are the main vulnerable groups for the identification of low temperature,low temperature humidity index and low wind-cold temperature.3.Based on the correlation mechanism between temperature,relative humidity,wind speed,sunshine hours and infectious power of mumps virus,the dynamic model with age structure can well fit the epidemic trend of mumps.Through this model,we can explain the important role of meteorological factors on the seasonal epidemic trend of mumps,as well as the important influence of contact rate among different age groups on the infectivity of mumps.4.The attribution risk of low temperature and extremely low temperature is higher in central Shandong,while high temperature and extremely high temperature mainly affect southwestern and central Shandong.After a comprehensive vaccination of school-age children in Shandong Province,the effective reproduction number of mumps in Shandong Province gradually approached to 1;temperature and temperature-related extreme weather events on the comprehensive risk of mumps in Shandong Province varied greatly in different regions,and the overall performance was that the risk was higher in the southern part of Shandong Province.5.Through the systematic analysis of epidemiological characteristics,effect analysis and regional risk assessment of mumps in Shandong Province,we can make early warning and prediction of high incidence and high risk cities based on meteorological factors and generalized additive model.The model has a good prediction effect and can accurately carry out early warning when the epidemic of mumps is stable and on the rise.This method is simple and practical.It can be used for accurate prevention and control of mumps in Shandong Province,and can be extended.Innovations1.By using the methods of descriptive,analytical and theoretical research,this paper explores the influence of meteorological factors on the incidence of mumps in different levels,and makes a comprehensive risk assessment of each prefecture and city.This paper constructs a research system for accurate prevention and control of mumps in Shandong Province by using meteorological factors,which provides a scientific basis for the prevention and control strategy of mumps.2.A dynamic model of mumps combined with meteorological factors was constructed,and the theoretical study of meteorological factors in mumps propagation mechanism was carried out firstly.Compared with the analytical research method,the model takes into account the effects of contact rate and vaccine vaccination rate among different age groups,and meteorological factors have a higher degree of explanation for the number of mumps cases.3.By using the comprehensive index of temperature and meteorological factors including temperature,the vulnerable population with the incidence of mumps which needed to be paid attention to by the relevant epidemic prevention departments was identified. |
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