Study On The Dynamic Model Of The Transmission Of Kala-azar And Quantitative Prevention And Control Strategies In Kashgar,Xinjiang

Objective:Kala Azar has been prevalent in Kashgar of Xinjiang for years,which has broken out many times.It is of great importance to estimate the characteristic parameters of infectious disease transmission for optimizing the control and intervention measures during the epidemic period.In this paper,the real-time effective reproduction number of kala Azar is estimated by the actual incidence data of Kashgar.In order to understand the transmission dynamics of kala Azar,as well as the overall epidemic trend of which,a dynamic model has been established to master the long-term prediction of kala Azar in Kashgar.At the same time,the key factors affecting the spread of the disease are quantitatively simulated,which provides a theoretical basis for the prevention and control of kala Azar.Methods:（1）The estimation of real-time effective reproduction number plays an important role in the epidemic of diseases.According to the monthly case data of kala-Azar in Kashgar of Xinjiang from 2004 to 2016,we divided the time before and after the outbreak into four stages.At the same time,the Bayesian method is used to estimate the real-time effective reproduction number of kala-azar at different times.（2）The mathematical model is established according to the actual case data and transmission route of kala Azar.Through the stability theory of differential equations and dynamic system theory,the dynamic behavior of the model is studied,and the law of disease transmission is revealed theoretically.Using R language and Matlab statistical analysis software to simulate the data and predict the epidemic trend of kala Azar,and estimate the model parameters.According to the results of sensitivity analysis,the key parameters affecting Kala Azar were found out to seek the best control strategy.Results:（1）The average reproduction number of the four stages were 1.02（0.83,1.24）;1.11（0.64,1.84）;0.92（0.68,1.16）and 1.20（0.57,2.42）,respectively,and real-time reproduction number reached the maximum of 3.07（2.09,4.25）in September 2014.The change trend of the real-time effective reproduction number was stable in the first and third stages,and increased abruptly in the second and fourth stages,and the change trend fluctuated greatly,indicating that the spread of kala-azar in Kashgar was increasing at this time..（2）According to the dynamics model of kala-azar,the fitting evaluation criteria the（Mean Absolute Percentage Error（MAPE=24.18%）and Root Mean Square Error（RMSPE=38.23%））are obtained,which indicated that the model was reasonable to fit the incidence data of kala-azar disease in Kashgar area;the prediction results of the model showed that the cumulative incidence continued to increase,but its growth rate gradually decreased,which means that the annual number of cases of kala-azar is gradually decreasing.The basic reproduction number R₀=1.76（95%CI:1.49-1.93）indicating that the disease will continue to be prevalent in Kashgar in a short time and cannot be completely eliminated.The results of sensitivity analysis showed that the transmission rate between sand flies and dogs（?₃、?₄）had the greatest impact on the basic reproduction number₀R,while the transmission rate from infected sandflies to susceptible individuals（₁?）and the transmission rate between sandflies and dogs（?₃、?₄）had the greatest impact on the number of cases of kala-azar（I）.Conclusion:According to the analysis results,it is feasible to monitor the real-time effective regeneration number,which can reasonably evaluate the current prevention and control measures,and provide useful information for public health departments,so that relevant departments can understand the situation and determine effective mitigation strategies in time;at the same time,the the results of established dynamic model show that the model fitting results can reasonably reflect the prevalence of kala-azar in Kashgar,Xinjiang;According to the sensitivity analysis results of the parameters,in order to effectively control the epidemic of kala-azar in the Kashgar,the mutual transmission between sandflies and dogs should be greatly reduced（such as environmental clean-up,insecticide sprayed around building,insecticide releasing dog collars and dog vaccinations）.In order to reduce the bite of sandflies on people,people can use insecticidal bed nets and try not to go to the wild areas where sandflies are prone to be active.At the same time,the local government should conduct public education on dangers and prevention of kala-azar for people.