| Background:Syphilis is a chronic contagious disease.The pathogen is a Treponema pallidum, which is a serious human pathogenicity of spirochetes, and it can injure all of organs and produce various symptoms. The main route of transmission is blood transmission, sexual transmission and mother to child vertical transmission. Early treatment is effective for syphilis, but tertiary syphilis can lead to more advanced organ damage and healing hardly, and can be dead. In the "the prevention and treatment to Communicable Disease of the People's Republic of China",syphilis is managed as a B disease.Syphilis remains a global problem with an estimated 12 million people infected each year, despite the existence of effective prevention measures, such as condoms,and effective and relatively inexpensive treatment options.And these new infections more than 90% occurred in developing nations.. Public health authorities all over the world have reported substantial rises in cases of syphilis in the past 10 years.This has been coupled with an increase in unsafe anal sex in men who have sex with men (MSM).In addition, commercial sex workers,increased population mobility, multiple sex partners has also led to increased incidence of syphilis.In China, from the early 90s of last century, the reported incidence of syphilis began to increase rapidly, in the year 2000 -2,004, it appeared plateau and then since 2005,it has a linear upward trend.Shenzhen has also a heavy burden of disease syphilis, and according to preliminary estimates,the number of infections more than 80,000.Since 90s in 20th century, the incidence of syphilis soared in Shenzhen, because of the change of the concept of people's sexual attitudes and the increase of the female sex workers and drug abuse.In Shenzhen, from 1983 to 1993 the incidence showed low prevalence (2/100000 below), since 1994 it doubled, particularly since 2004, the incidence of syphilis steadily increased, and to the end of 2008, it reached 49.80/100,000, which located first-class city throughout Guangdong Province, and it was 1.49 times than the average incidence levels (33.44/10 million) of Guangdong Province,and 2.36 times than the national average incidence levels (21.08/10 million). And in 2008,6,295 cases had reported.Syphilis had secondary incidence of the 37 infectious diseases.And it has become a public health problem in Shenzhen.In recent years, the incidence of elderly STD in the world also rised. Older people are increasingly likely to be single or undergoing relationship changes (for example, divorce, separation or widowed) and at increased risk of STIs as they are less likely to consistently use condoms. Research has shown that both male and female international travellers are increasingly engaging in unprotected sex while travelling abroad or returning to their country of origin. Although this is mainly documented in young people, older people are not exempt. It is recognised that young people have multiple and at times concurrent sexual partners and that these include older people.In recent years, monitoring data of syphilis showed an upward trend in the incidence in older people.The elderly may be the links of the spread of sexually transmitted diseases and HIV, and we should pay attention to the syphilis in old people.There are externalities in the prevention and control of sexually transmitted diseases, as a public goods,there are market losses in the allocation of resources of STD.At this time the government intervention should be used to realize the optimization of resources,but because information is not complete, budget constraints and other conditions of the restrictions, the government's intervention is not almightyl,and the government's ability of decision-making can also fact the ineffectiveness of the prevention of the sexually transmitted diseases.Therefore, we need to analyze government decision-making and improve decision-making ineffectiveness.The prevention and control of STD continues to enhance in recent years, and the financial input increased too, but the incidence of syphilis and other sexually transmitted diseases and the number of reported cases increased, so we need to know the status of syphilis and the stages of the prevalence, because the different stages of sexually transmitted diseases should adopt the different prevention and control strategies. We can optimize the allocation of resources base on the understand the current situation of syphilis, and we can better prevent and control the spread of syphilis and other sexually transmitted diseases, and improve our financial performance.Objective:A good strategy to sexually transmitted diseases is essential to preventing and controlling the spread of STD, but to develop appropriate control strategies, we need grasp the current incidence of syphilis, temporal and spatial distribution, trends and cost-effectiveness of various interventions.The main purpose of this study are:(1)To find out the incidence of syphilis and the temporal and spatial distribution in recent years in Shenzhen, and to service for the development of policy of sexually transmitted diseases.(2) Establisht the transmission system dynamics model of syphilis in Shenzhen and predict the trends in syphilis incidence,,referent to the prevention and control policies. (3)Simulate the control effects and cost-effectiveness of all prevention in Shenzhen.(4) Establish the ARIMA time series forecasting model of aged 50 and over male syphilis in Shenzhen.Methods:(1)The data from"disease surveillance reporting information management system" in the"China Disease Prevention and Controlling Information System",2004-2010, was used in this study. GIS data was collected from Shenzhen digital map.Population and economic data was acquired from the Municipal Bureau of Statistics of Shenzhen.Behavioral data was collected from special survey and documentation.(2) In this study, space epidemiological methods and space-time scan statistics for analysis of syphilis are use to analysis the incidence of syphilis in Shenzhen, and find out the time and spatial distribution characteristics. These process finished by the space-time scan statistics software SaTSCan.(3)Using VENSIM software, system dynamics model of the syphilis in Shenzhen is established, and in the model,we simulate the sexual relations network of syphilis among the core groups-female sex workers (FSWs), bridge groups-multi sexual partners, and we also simulate the condom use, health intervention, screening, economic factors and other population control policies, many parameters of the model obtained through investigation.(4) We use the classical method of cost analysis to compute the cost of various interventions.We took special investigation by randomly selecting 10 Shenzhen STD prevention and control institutions.Using these survey data, we can calculate the unit costs, and then calculated the total cost. Then through the establishment of a system dynamics model,,we simulate the cost-effective of various control measures by changing the parameters of the model.(5)We use time series analysis method to establish the ARIMA prediction model of 50 years and older men syphilis in Shenzhen. Time series analysis process by software Eviews5.0.Results:(1)By the purely spatial analyses, the clusters were at the junction of the Baoan District and Nanshan District(such as Xinan, Xixiang, Nanshan and Nantou street office) and in the region near Hong Kong(such as Dongmen, Shekou, and Futian street office), as well as in the other streets where entertainment industry is relatively developed (such as Longhua, Huafu,Huangbei and Cuizu street office).The clusters have little change in the first four years.The most likely cluster for each year are located in Longhua (2005, P≤0.001, RR=3.34), Cuizu (2006, P≤0.001,RR=9.59), Huafu(2007,2008 years,P≤0.001,RR were 4.18 and 4.75).By space-time scan analysis, we found 10 significant clusters, which are similar to the purely spatial analyses, but there are also regional differences, the most likely cluster are located in Minzhi and Bantian street office between 2007 and 2008.There are three clusters (Minzhi Bantian,Dalang)in these 10 significant clusters were no-significant clusters by the purely spatial analyses,others were significant clusters too.We found five early warning signals by prospective space-time permutation scan statistic using primary syphilis and secondary syphilis cases in Shenzhen between November and December in 2005.(2) By the test using the historical data of 2004-2009 reported incidence, we found the absolute error of the model simulated value and historical value ess than 5%.It means the SD model fit the actual data well and the model can be simulated prediction and policy analysis. (3)Through the simulation analysis by the system dynamics model, we found that all interventions can reduce the number of infections.The modeling results indicate that condom use among FSWs increased to 75% and 95% in 2010, approximately need 2,436,700 yuan and 3.8581 million yuan investment, and measure the input 79.53～89.7 yuan each, can reduce one case,and the per cost of the reduction of one case in the 95% of condom use lower than 75%.The modeling results indicate that condom use among multiple sex partners increased to 75% by raising public awareness of condom usage among multiple sex partners, we need 140.93 yuan to reduce the one case of syphilis.By simulation to improve screening rates among FSWs to control the spread of syphilis found that screening rate of 25%,the total cost required 358,300,30% screening rate required 430,000 yuan. By strengthening the screening to prevent syphilis among FSWs, every cost to avoid one case of syphilis infection was 280.68～398.60 yuan. All the screening before the surgery takes about 972 000.Through the pre-operative screening, the cost of each reducing one case of syphilis is 204.42 yuan. If we maintain the existing control effect, the requirements for prevention and treatment of syphilis in 2010 was about 2.8388 million yuan.(4) The benefit estimate by the cost of patients with syphilis. Randomly survey 50 patients who attended STD clinics for treatment of syphilis, found out that each case of syphilis patients spend 959.46 yuan. Through simulation analysis,we found pre-operative screening, FSWs health education, public awareness, FSWs population screening and other preventive measures of benefit to cost ratio, respectively:4.69,10.7,9.24, 3.42.(5)The incidence of syphilis in 50 and more years old people increased in recent years.By space-time scan analysis, we found 2 significant clusters(Lianhua and Meilin street office),.ARIMA (0,1,1) (0,0,1)12 model can reflect the trends of men syphilis over the age of 50,and P values were more than 0.05 after teste.Conclusions:(1)The cluster of syphilis were in the Longhua, Xixiang, Xinan Street of Bao'an District,.and in the Nanshan, Nantou, Shekou street of Nanshan District, and in Futian, Huafu street of Futian District, and in Cuizu, Dongmen,Huangbei street of Luohu District. The clusters have little change in recent years,it suggesting that financial investment should be strengthened in prevention and control of STD. And we should focus on investigating the reasons for the clusters of syphilis in recent years, and take appropriate control measures.(2)Shenzhen syphilis transmission system dynamics model can fit the characteristics of the spread of syphilis in Shenzhen well.We found that the case of syphilis increased from 2010 to 2015 through simulation, and found that we need 2,838,800 yuan to maintain the existing control effect Some.(3)In infected persons, multiple sex partners accounted for the major part of the crowd, followed by the FSWs population. Regular sexual partners also are predicted that the number of people infected will continue to increase between 2010-2015.(4) To strengthen health education to change high-risk behavior is the most cost-effective control strategies.We found that pre-operative screening is a very important measure to control the general population infection, we should be vigorously promoted, and adopted them into the scope of medical insurance reimbursement, and improve screening rates. The major strategies to the high-risk groups is improving coverage and increase the number of interventions to maintain condom use rates to remain at relatively high levels. (5)The incidence of syphilis in 50 and more years old people increased in recent years.By space-time scan analysis, we found 2 significant clusters(Lianhua and Meilin street office). ARIMA (0,1,1) (0,0,1)12 model can reflect the trends of men syphilis aged 50 and above.
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