Serial Cross-sectional Studies Of HIV/STIs Infections Among Female Sex Workers In One City Of Yunnan Province

Multi-angle and deeper purposes of analysis were performed to exlore the prevlaencs of HIV/STIs among female sex workers (FSWs) in one city of Yunnan province in China. According to the data analysis of field epidemiology and lab testing results, unsafe sex and illicit drug use were two main risk and stimulative factors to HIV/STIs infection and transmission among FSWs. The superposition of these two behaviors can not only speed up HIV/STIs spreading in FSWs and drug users, but also enhance the'bridge'effects of HIV/STIs spreading from high risk populations to general populations. Effective and positive measurements should be taken to reduce high risk behaviors in FSWs. Controlling HIV/STIs transmissions in FSWs was main content to decrease the prevalent rates of HIV/STIs in general population and to protect people's health.Objectives: To explore HIV/STIs infections among FSWs and to find out its transmission rules and trends; to explore HIV/STIs related factors among FSWs, so as to provide scientific evidence for HIV/STIs prevention and intervention strategies; to test HIV-1 gene subtype among FSWs, so as to track HIV-1 transmission route and predict its pandemic trend.Methods: Serial cross-sectional studies and cohort study were performed in one city of Yunnan province during March, 2006 to April, 2008. Convenience sampling was used to collect FSWs'informations on demographic, sexual behaviors, drug use behaviors, other related risk behaviors, HIV/STIs related knowledge, and health seek behaviors every six months. At the same time, HIV and STIs (including HSV-2, Chlamydia trachomatis, gonorrheae, syphilis and trichmonad) were tested. After obtaining HIV/STIs infection rates in each cross-sectional study, we analysed variation trends of infection rate of every disease, and explored related risk factors of HIV/STIs infection among FSWs. HIV/STIs incidence rates and variation trends of related risk behaviors were analyed using data in cohort study which was performed during the repeated cross-sectional studies.HIV-1 gene subtypes were tested which were performed in reference laboratory in National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention. SPSS12.0 and SAS9.2 softwares were used to analyze data. Unconditional univeriate logistic regression and multivariate logistic regression were performed to analyze HIV/STIs, HIV related risk factors separately. Variables with p-value≤0.20 in the univeriate logistic regression analysis were put in the model of multivariate logistic regression analysis. Meanwhile, interactions between each variable in the model were analyzed. Forward stepwise was used to select parameters with p<0.05 to enter and p>0.10 to exclude. OR and 95% confidence interval were calculated for each parameters in the final model. Test of goodness of fit was performed to test model fitness. GEE model was performed to analyze HIV/STIs and HIV related risk factors separately in the longitudinal data. Variables with p-value≤0.20 in the univeriate GEE analysis were put in the model of multivariate GEE analysis. Meanwhile, interactions between each variable in the model were also analyzed. Two sides probabilities of p<0.05 were used as significant levels. Two sides probabilities of 0.05 < p <0.10 were used as marginal significant levels.Results:1. In the five cross-sectional studies, the median age (±Quartile) of FSWs was 24.0±8.5 years old, 25.0±9.0 years old, 25.0±11.0 years old, 25.0±10.0 years old, and 28.0±13.0 years old, respectively. Most of FSWs were Han ethinicity, accounting for 66.9%, 69.5%, 70.9%, 71.5%, and 73.8% in the studies, respectively; followed by Yi ethinicity, Hui ethinicity, Hani ethinicity, and et al. Many FSWs had low education levels. In the studies, there were 52.2%, 50.0%, 55.7%, 52.1%, and 49.6% FSWs completed middle school, respectively; followed by primary shool/ illiterate, senior high shool and above. Many FSWs were single with percentage of 50.2%, 44.9%, 48.1%, 41.7%, and 36.5%, respectively; followed by cohabited and married. Most of FSWs lived in the rented rooms at present, accounting for 66.5%, 68.2%, 68.8%, 60.5%, and 66.8%, respectively. A lot of FSWs came from other cities which were not Kaiyuan city, accounting for 77.9%, 79.5%, 75.5%, 72.0%, and 69.2%, respectively.2. HIV infection rates among FSWs in the five cross-secitonal studies were 10.3%, 11.9%, 13.0%, 12.4%, and 11.2%, respectively. The infection rates of STIs were as follows: syphilis: 7.5%, 8.4%, 8.8%, 6.7%, and 4.8%, respectively; trichmonad: 10.6%, 9.0%, 8.2%, 6.1%, and 2.1%; gonorrheae: 8.3%, 5.9%, 5.6%, 6.6%, and 8.3%; Chlamydia trachomatis: 25.9%, 20.0%, 18.1%, 22.5%, and17.4%; HSV-2: 68.1%, 68.5%, 71.1%, 67.0%, and 63.5%; STIs (excluding HIV, if one of the tested diseases result was positive, then the result of STIs infeciton was positive ): 79.1%, 76.0%, 78.6%, 74.9, and 73.3%. The trends of infection among syphilis, trichmonad, Chlamydia trachomatis, and STIs were significantly decreasing. Two new infected HIV occurred during two years study, with cumulative incidence rate of 3.39%. Three new infected HSV-2 occurred during two years study, with cumulative incidence rate of 20%.3. Behaviors of unsafe sex and illicit drug use were two main risk and stimulative factors to HIV/STIs infection and transmission among FSWs. In the five corss-sectional studies, FSWs who did not use condoms consistently in the commercial sex behaviors in the last week accounted for about 15.9%, 12.8%, 13.8%, 13.6%, and 13.3% , respectively. FSWs who never use condoms with regular sexual partners accounted for 47.3%, 44.1%, 46.7%, 41.1%, and 38.7%, respectively. FSWs who used drugs illicitly accounted for 16.3%, 18.9%, 21.3%, 23.6%, and 18.1%, respectively.4. Number of clients, duration of sex work, number of work locations in the last year, price level of FSWs, condom using in the commercial sex, having experiences of extracting/ filling/ washing tooth in the last five years, tattoo, drink, drug using were influence factors for HIV/STIs infection among FSWs. 5. CRF₀8BC,CRF₀7BC and C were main HIV-1 gene subtypes among FSWs. CRF_BC subtype accounted for moset, with percentage of 79.5% (including CRF₀7BC and CRF₀8BC); followed by C subtype 10.7%, CRF01_AE subtype 0.9%.Conclusions: The prevalence of HIV/STIs were high among FSWs. Unsafe sex and illicit drug use were two main risk and stimulative factors to HIV/STIs infection and transmission among FSWs. Number of clients, duration of sex work, number of work locations in the last year, price level of FSWs, condom using in the commercial sex, having experiences of extracting/ filling/ washing tooth in the last five years, tattoo, drink, drug using were influence factors for HIV/STIs infection among FSWs. CRF₀8BC,CRF₀7BC and C were main HIV-1 gene subtypes among FSWs. Controlling HIV/STIs transmissions in FSWs was main content to decrease the prevalent rates of HIV/STIs in general population and to protect people's health. The innovations of this study were as follows: in the design, corss-sectional study and longitudinal study were combined to build a cohort among FSWs, so as to implement prospective cohort study in special populations; in the method of analysis, traditional logistic regression and GEE model were used to analyze HIV/STIs related influence factors among FSWs in different aspects, separately; epidemic survey and HIV-1 gene subtype testing were used together to explore HIV pandemic situations among FSWs.