Conclusions. The "bridging effect" for HIV transmission is evident. Variables predicting condom use during commercial sex are multidimensional. Integrative programs are hence required. Methadone clinics may offer a platform for offering such services to IDU-FSWs. The performance of the TPB could be enhanced by addition of external variables; its applicability varies according to the wellbeing status of the IDU-FSWs. Future randomized control studies are warranted to design effective evidence-based programs targeting IDU-FSWs. / Introduction. Injecting drug users (IDUs) drive the HIV epidemic in China. Female injecting drug users who are sex workers (IDU-FSWs) is a strategic "bridge population" for HIV transmission from the IDU to non-IDU populations. Background characteristics, health behavioral theories (e.g. the Theory of Planned Behavior, TPB), drug dependence, economic pressure, psychological problems, social support and gender power are potential predictors of condom use during commercial sex among IDU-FSWs. Most of these associations have not been investigated in China or elsewhere, and the TPB has not been applied to HIV-vulnerable populations in China. A knowledge gap exists. / Objectives. This study validated two instruments measuring severity of drug dependence. The prevalence of inconsistent condom use among IDU-FSWs and its associations with the aforementioned variables were investigated. The hypotheses that different blocks of variables would have independent effects on condom use during commercial sex, and the effects of TPB-related variables on condom use would be moderated by some external variables (e.g. severity of drug dependence) were tested. / Results. The Opiate Addiction Severity Inventory-Revised (OASI-R) was fully validated in the Study I. Around 6.8% of IDU-FSWs were HIV positive and respectively 48% and 64% of them practiced needle sharing and unprotected commercial sex (last six months). After adjusting for significant background variables, the five TPB-related variables (AOR=0.43 to 1.92, p<0.001), severity of drug dependence (AOR=1.05, p<0.01), economic pressure (AOR=1.07, p<0.05) and all studied psychosocial variables (e.g. depression, social support and gender power; AOR=0.70 to 1.67, p<0.05) were significantly associated with condom use during commercial sex. / Subjects and methods. Two cross-sectional studies were conducted. In Study I, 178 non-institutionalized drug users were interviewed in Dazhou, Sichuan. In Study II, 281 non-institutionalized IDU-FSWs were interviewed in Dazhou, Sichuan and Hengyang, Hunan, using snowballing method and face-to-face interviews. Statistical methods such as hierarchical and interaction modeling, stratification analysis, ROC method were used in this study. / The final hierarchical model predicting condom use during commercial sex included variables coming from four blocks of independent variables, with ROC area = 94% and sensitivity/specificity = 0.84/0.91. A "Wellbeing Status Index" moderated the associations between some of the TPB-related variables and condom use during commercial sex. / Gu, Jing. / Adviser: Joseph T. F. Lau. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3462. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 228-246). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

HCV genotype 6 is restricted in its distribution in South East Asia and it has been circulating for a long period of time. Phylogenetic and phylodynamic analysis on epidemic history of HCV focusing genotype 6 in South East Asia was explored, taking references from the pattern delineated in Liuzhou. Our results show that the date of most recent common ancestor (MRCA) of the whole HCV genotype 6 was estimated to be 100 years ago or more. There was an obvious increase of effective number of HCV genotype 6 infections in the part 20 years. Epidemic history of Subtype 6a and 6e/6d also showed the similar time course as that of the genotype 6. Interestingly, there was an increase of effective number of infections around 15-20 years ago which was maintained in the following decade for subtype 6a as well as 6e/6d. This specific pattern was consistent with the history of needle sharing in South East Asia, where the number of IDUs increased in the 1980s. The epidemic then spread to Southern China as evident by the increasing trend in Liuzhou. There was an exponential growth around 5 years ago involving subtype 6a predominantly, which might remain prevalent in Southern China in the coming decades. In conclusion, the study has shed new light on the transmission history of HCV, providing an explanation on the emergence of HCV genotype 6 in South East Asia. / HCV infection is an important public health problem associated with blood transfusion and needle-sharing in injection drug users (IDU) in Southern China. An understanding of the epidemiological pattern of the HCV infection, in conjunction with the transmission dynamics, would be beneficial for supporting effective prevention and control. This is accessed using a combination of molecular and public health approaches. / Through the Liuzhou Methadone Clinic, a total of 117 IDUs were recruited from Guangxi, Southern China. A majority of the IDUs (96%) were HCV antibody positive, of which 21% were HIV infected. Unlike HCV monoinfection, there was spatial heterogeneity in the distribution of HIV/HCV coinfection. The latter was also characterised by a higher prevalence of needle-sharing. Phylogenetic analysis of HCV revealed that genotype 6a was predominant in the study population. There were shorter genetic distances among the 6a samples compared to 3 other HCV genotypes/subtypes, 1a, 3a, and 3b. Our results suggested that HIV and HCV were both introduced at around the same time to the IDU populations in Southern China, followed by their differential spread as determined by the biologie characteristics of the virus and the intensity of behavioural risk. This pattern might be different from that in other South East Asian countries where HCV infections have probably predated HIV. / Tan, Yi. / Adviser: Kung Hsiang-fu. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3404. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 164-178). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Li, Huizhen. / "March 2008." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 139-150). / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgement --- p.vii / Abbreviations --- p.ix / Introduction --- p.1 / Chapter 1.1 --- HIV and AIDS --- p.4 / Chapter 1.1.1 --- HIV Transmission Routes --- p.5 / Chapter 1.1.2 --- HIV Related Risk Behaviors --- p.6 / Chapter 1.2 --- HIV Burden --- p.7 / Chapter 1.2.1 --- HIV Infection in China --- p.7 / Chapter 1.2.2 --- HIV Infection in Hong Kong --- p.9 / Chapter 1.2.3 --- Methadone Treatment in Hong Kong --- p.10 / Chapter 1.3 --- Objectives and Hypothesis --- p.14 / Chapter 1.4 --- Organization of This Thesis --- p.15 / Literature Review --- p.16 / Chapter 2.1 --- Search Methods --- p.18 / Chapter 2.1.1 --- Formulating Review Questions --- p.18 / Chapter 2.1.2 --- Search Strategy --- p.19 / Chapter 2.1.3 --- Inclusion and Exclusion Criteria --- p.21 / Chapter 2.2 --- Assessing the Quality of Studies --- p.22 / Chapter 2.3 --- Search Results --- p.23 / Chapter 2.3.1 --- Descriptive Summary --- p.25 / Chapter 2.3.2 --- Critique of Reviewed Articles --- p.33 / Chapter 2.4 --- Implication on Planning of Current Study --- p.37 / Chapter 2.4.1 --- Summary of Reviewed Articles --- p.37 / Methods for Exploring Predictors of HIV Risk --- p.40 / Chapter 3.1 --- Data Source --- p.42 / Chapter 3.1.1 --- Data Management in Methadone Clinics --- p.42 / Chapter 3.1.2 --- Source of Data --- p.43 / Chapter 3.2 --- Data Transformation --- p.45 / Chapter 3.3 --- Framework for assessing outcome --- p.48 / Chapter 3.3.1 --- Study population in different analyses --- p.48 / Chapter 3.3.2 --- Risk Score --- p.49 / Chapter 3.3.3 --- Independent Variables --- p.50 / Chapter 3.4 --- Generalized Linear Model --- p.52 / Chapter 3.5 --- Logistic Regression Model --- p.54 / Chapter 3.6 --- Multilevel Analyses --- p.55 / Chapter 3.6.1 --- Variables --- p.56 / Chapter 3.6.2 --- Definition of 'Neighborhood' --- p.56 / Chapter 3.6.3 --- Individual Variables --- p.60 / Chapter 3.6.4 --- Framework for Analyses --- p.60 / Chapter 3.7 --- Field Study --- p.63 / Results: Community Variation of HIV Risk --- p.65 / Chapter 4.1 --- Demographic Description --- p.67 / Chapter 4.1.1 --- Age distribution --- p.67 / Chapter 4.1.2 --- Gender Distribution --- p.68 / Chapter 4.1.3 --- Proportion of New Admission --- p.72 / Chapter 4.2 --- Drug Taking Profile --- p.74 / Chapter 4.2.1 --- Heroin Use --- p.74 / Chapter 4.2.2 --- Injecting Heroin Users --- p.77 / Chapter 4.3 --- HIV related risk behaviors --- p.81 / Chapter 4.3.1 --- Injection History --- p.81 / Chapter 4.3.2 --- Risky Injection Practices --- p.87 / Chapter 4.3.3 --- Sexual Behaviors --- p.93 / Chapter 4.4 --- Correlation between Demographics and Risk Score --- p.94 / Chapter 4.4.1 --- General Linear Regression Model Coefficient --- p.94 / Chapter 4.4.2 --- Risk Predictors in Logistic Regressions --- p.95 / Chapter 4.5 --- Neighborhood Effect --- p.100 / Chapter 4.6 --- On-site Observation --- p.103 / Chapter 4.6.1 --- Demographic Variations --- p.103 / Chapter 4.6.2 --- Drug Use Variations --- p.104 / Chapter 4.6.3 --- Social Background --- p.105 / Discussion --- p.111 / Chapter 5.1 --- Neighborhood Effect --- p.113 / Chapter 5.1.1 --- Variation across Communities --- p.113 / Chapter 5.1.2 --- Implication on Social Network of IDUs --- p.115 / Chapter 5.2 --- Decline of Admissions --- p.117 / Chapter 5.2.1 --- Decrease of New Admissions --- p.117 / Chapter 5.2.2 --- Decline of Readmission in 2003 --- p.119 / Chapter 5.3 --- Female IDU Population --- p.121 / Chapter 5.4 --- Limitations --- p.125 / Chapter 5.4.1 --- Importance of Individual Level Variables and Community Level Variables --- p.125 / Chapter 5.4.2 --- Reliability of Self-reported Data --- p.126 / Chapter 5.4.3 --- Duplicates of Readmissions --- p.126 / Chapter 5.4.4 --- Definition of Syringe Reuse --- p.127 / Chapter 5.4.5 --- Choice of Models --- p.129 / Conclusion and Future Directions --- p.131 / Chapter 6.1 --- Summary of Results --- p.133 / Chapter 6.2 --- Implication of results --- p.134 / Chapter 6.3 --- Future Directions --- p.136 / Bibliography --- p.139