The SIR Model Of HiV/AIDS Epidemic In Injection Drug Users In Chongqing

Objective Describe HIV/AIDS epidemic of high-risk groups in Chongqing,Evaluate the intervention strategies and measures of HIV/AIDS epidemic of IDUs in Chongqing, establish SIR model to simulate the HIV/AIDS epidemic of IDUs in Chongqing and predict the trend of HIV/AIDS epidemic of IDUs in Chongqing.Methods Use SIR model to simulate the HIV/AIDS epidemic and add population dynamics factors, needle and syringe programmes, opioid substitution therapy and ART in the model toanalysis the influenceof interventions on HIV epidemic of IDUs in Chongqing. Parameters in the model extract from 2007-2012 HIV/AIDS prevention and treatment annual reports in Chongqing, Some parameters which could not extract from annual reports were estimated by Monte Carlo simulation and literature research. The key indicator of evaluating HIV/AIDS epidemic trend is the basic reproduction number. The SIR model formula is derived by Wolfram Mathematica 9.0 software. Monte Carlo simulation was implemented by R software. Data analysis was implemented by Excel 2010 and SPSS19.0.Resluts From 2006 to 2012, the main HIV infection routes were intravenous drug use, heterosexual and homosexual transmission routes. The annual average HIV infection rate of the IDUs was 8.42%(95%CI: 7.82%-9.03%).By SIR model to simulate the HIV/AIDS transmission characteristics of IDUs in Chongqing, this study has got the following results: when the coverage rates of needle exchange, ART and methadone maintenance treatment are 0, the basic reproduction number 0R will be 2.05. When the coverage rates of needle exchange and ART in IDUs living with HIV group are 0 and the coverage rate of methadone maintenance treatment in IDUs living with HIV group increase from 0 to 0.05, the basic reproduction number0 R will reduce 0.5. When the coverage rates of needle exchange and methadone maintenance treatment in I group are 0 and the coverage rate of ART in IDUs living with HIVgroupincrease from 0 to 0.05, the basic reproduction number 0R will reduce 0.5. However, when the coverage rates of methadone maintenance treatment and ART in IDUs living with HIV group are 0 and the coverage rate of needle exchange in IDUs increase from 0 to 0.2, the decrease of basic reproduction number 0R was less than 0.5. Consideration the actuality and model simulation, the optimal intervention strategy is methadone maintenance treatment coverage in IDUsliving with HIVgroup is 0.105 and antiviral treatment coveragein IDUs living with HIVgroupis 0.05, then the basic reproductive number is less than 1.The correlation coefficient of HIV infection rate of IDUs from model simulation and actuality was 0.77(p<0.05).Conclusion The study has described the high-risk groups of HIV/AIDS epidemic in Chongqing and established the SIR model to simulate and predict HIV/AIDS epidemic trendof IDUs in Chongqing. Adding intervention measures targeted HIV/AIDS epidemic of IDUs in Chongqing(needle exchange project, methadone maintenance therapy and antiviral treatment projects)in the model, we can knowthe influence of different intervention projects and intervention intensity on the epidemic from the model.Through the model simulation and realistic feasibility, this study proposed a best intervention strategy.The fitting degree of model simulating data in the study and actual data is high, this shows that the SIR model on the analysis of the HIV/AIDS epidemic has a good effect.Compared with other HIV/AIDS epidemic model, SIR model can directly reflect the influence of the behavior of epidemic factors and intervention factors on the epidemic, and the basic reproductive number in the model can be used to predict the trend of the HIV/AIDS epidemic.