Study On The Epidemic Dynamics Of Japanese Encephalitis And The Development Of Corresponding Forecast And Precaution Model In Gansu Province

Objectives To understand the distribution characteristics and changing trend of Japanese Encephalitis?JE?cases,identify high-risk population,seasons and regions,and use different models to predict and analyze the epidemic trend and intensity of JE in children and adults.So as to provide a theoretical basis for targeted prevention and control of JE in Gansu Province.Methods The data of confirmed cases were mined by descriptive epidemiological method.The characteristics of high-risk population and seasons distribution were analyzed by case composition and dynamic series.The spatial distribution characteristics were analyzed by incidence and map.The theoretical epidemiological study was carried out to construct the optimal predictive model for different target groups.The SARIMA and SARIMA-SVR combined models were established to quantitatively predict the incidence of JE in children and adults.By using MPM,a qualitative early warning model was established to calculate the warning thresholds,combined with the quantitative prediction values,so as to explore the trend and intensity of JE in Gansu Province.Results 1.There were 653 confirmed cases with JE in 2005-2017,56 cases died.The average incidence was 0.1917/10,000,the mortality was 0.0164/10,000,and the fatality was 8.58%per year.The incidence was at a low level,basically the same as that of the whole country,with an average develop speed of 116.98%and an average growth speed of 16.98%in 2005-2014.The incidence exceeded the national average for the first time in 2014.In 2017,it reached 16.34 times Chinese average incidence of JE.With an average develop speed of 196.53%and an average growth speed of 96.53%in 2014-2017.2.The JE cases was more female than male,and the ratio was 0.99:1.The occupational distribution was mainly farmers,accounting for 67.08%.The high risk population gradually changed from children to adults,especially in the 40-64 years old.The case composition of children under 15 years old decreased from 60.00%in 2005 to 3.90%in 2017,whereas adults over40 years old increased significantly from 20.00%in 2005 to 70.90%in 2017.3.The peak of onset season of cases was from July to September,accounting for 97.70%,of which August was the most,accounting for 76.72%.In the popular season,the number of reported cases per week in adults was more than children,especially in 40-64 years old.4.From 2005 to 2016,the disease mainly occurred in the Southeast Gansu.Since 2017,the epidemic area has expanded and spread to the Midlands Gansu.In 2017,the cases were reported in all regions except Jinchang City,Jiayu Guan City and Jiu Quan City.And there mainly was adult cases in every regions,especially those 40-64 years old.Children cases under 15 years old all occurred in the Southeast Gansu.5.The RMSE,MAE and MSE values of the SARIMA and SARIMA-SVR models were25.88%and 25.87%,14.49%and 14.48%,6.70%and 6.69%in the prediction of incidence of the whole population.The values in children were 3.95%and 3.69%,1.80%and2.00%,0.15%and0.14%.The values of RMSE,MAE and MSE in adults were 30.52%and 30.27%,15.84%and15.66%,9.21%and 9.16%.The combined SARIMA-SVR models have better predictive effect than SARIMA models in different age groups.6.The quantitative prediction results showed that the incidence of JE is on the rise from September 2018 to December 2019.And the incidence of adults aged 15 or above is far higher than children.The peak season still concentrates in 7-9 months,reaching the peak in August.7.Qualitative predictive results showed that from September 2018 to December 2019?about1.3 epidemic years?,the incidence rate of all age groups was below P80 in October 2018,and the incidence of children in September 2018,June to July and September to October 2019 was below the P₈₀.The incidence of all age groups was higher than the‘x+2s'in Feburary to March and August in 2019.The incidence of the whole population and adults was even higher than the historical maximum in August 2019.Conclusions 1.In 2005-2014,the incidence of JE was stable at a low level.The incidence increased significantly since 2015,and the high-risk group gradually shifted from children under15 years old to adults over 40 years old.2.The peak of epidemic season was always from July to September.In the popular season,the number of reported cases per week in adults was more than children,especially in 40-64 years old.3.The hot-spots of JE was concentrated in the southeast,which has been expanding to the Midwest in 2017.There mainly was adult cases in every regions.While,children cases only occured in the southeast Gansu.4.The SARIMA-SVR model is better than the SARIMA model in predicting the incidence of JE in different age groups.The results suggest that the incidence will increasing continuously,and the incidence of adults will far higher than children.The epidemic seasonal peak will still concentrated during July to September,and the peak will reaches in August.In addition,the MPM early warning results suggest that we should be highly alert to the outbreak of adults with JE in August.