Modelling the spread of HIV/AIDS in China: the role of sexual transmission

Analysing the impact of migration on HIV/AIDS cases using epidemiological modelling to guide policy makers

In this paper, we present the impact of migration on the spread of HIV and AIDS cases. A simple model for HIV and AIDS that incorporates migration and addresses its contributions to the spread of HIV and AIDS cases was constructed. The model was calibrated to HIV and AIDS incidence data from Malaysia. We explore the use of Markov chain Monte Carlo (MCMC) simulation method to estimate uncertainty in all the unknown parameters incorporated in our proposed model. Among the migrant population, 1.5572e-01 were susceptible to HIV transmission, which constituted 67,801 migrants. A proportion of migrants, 6.3773e-04, were estimated to be HIV infected, constituting 278 migrants. There were 72 (per 10,000) migrants estimated to have had AIDS, representing a proportion of 1.6611e-08. The result suggests that the disease-free steady state was unstable since the estimated basic reproduction number R0 was 2.0906 and 2.3322 for the models without and with migration, respectively. This is not a good indicator from the public health point of view, as the aim is to stabilize the epidemic at the disease-free equilibrium. The advantage of introduction of migration to the simple model validated the true R0 and the transmission rate β associated with HIV and AIDS epidemic disease in Malaysia. It also indicates an approximately 12 percentage points increase in the rate of HIV infection with migration.

Change in China's SRB: A Dynamic Spatial Panel Approach

There has been some research on factors affecting China's rising sex ratio at birth (SRB), but the spatial dependence has been largely neglected. With China's census and sample survey data and the dynamic spatial Durbin model; we analyzed the changes in SRB in China. We found that SRB and its influencing factors were spatially correlated at the provincial level. For direct effects; urbanization significantly reduced SRB in this region; while strict family planning policies increased SRB in the local region. For indirect effects; the increase in per capita Gross Domestic Product and urbanization led to an increase in the SRB of the neighboring regions through population mobility. By comparison; educational improvement in one region benefited the neighboring provinces and reduced SRB.

Causes and Consequences of Drug Abuse: A Comparison Between Synthetic Drug and Heroin Users in Urban China

This article examined the differences in causes and health consequences between synthetic drug and heroin abuse in urban China. Two-group comparisons were conducted to quantify differences in individual characteristics, causes of drug use, and HIV/STI risky sexual behavior between synthetic drug and heroin users; logistic regressions were employed to assess the net effect of synthetic drug use on risky sexual behavior. Results revealed that causes of synthetic drug use differed from those of heroin use; a combination of the knowledge gap concerning the harmful impact of synthetic drugs and the lesser punishment for their use appeared a main reason behind the shift from heroin to synthetic drugs; and synthetic drug use was a significant and powerful risk factor for HIV/STI risky sexual behavior. Educational and behavioral interventions are urgently needed to prevent the initiation of synthetic drug use among users to reduce their HIV/STI risky sexual behavior.

Effectiveness of a Peer-Assisted Multicomponent Behavioral Intervention in HIV Risk Reduction Among Female Entertainment Workers in China

This study examined the effectiveness of a behavioral intervention that combined cognitive and social influence approaches. The intervention consisted of small group sessions targeting HIV knowledge, protection motivation, behavioral skills, and social influences of risk reduction. The control was an attention-controlled HIV/STI health education and counseling. Two-group comparisons were conducted to assess the effectiveness of the intervention; risk reduction over time was analyzed to determine the sustainability of the effectiveness. The analyses revealed that the intervention was effective in reducing/increasing HIV risk/protective behaviors and the effect was sustainable. While participants in the control reported a greater reduction/increase in risk/protective behaviors 3-month post-intervention, the initial strong effect quickly faded and completely disappeared 12-month post-intervention. By contrast, the moderate initial effect of the intervention was not only sustained but actually strengthened over time. The intervention was well received by participants and holds promise for HIV risk reduction behavior change among female entertainment workers in China.

A Markov Chain Monte Carlo Approach to Estimate AIDS after HIV Infection

The spread of human immunodeficiency virus (HIV) infection and the resulting acquired immune deficiency syndrome (AIDS) is a major health concern in many parts of the world, and mathematical models are commonly applied to understand the spread of the HIV epidemic. To understand the spread of HIV and AIDS cases and their parameters in a given population, it is necessary to develop a theoretical framework that takes into account realistic factors. The current study used this framework to assess the interaction between individuals who developed AIDS after HIV infection and individuals who did not develop AIDS after HIV infection (pre-AIDS). We first investigated how probabilistic parameters affect the model in terms of the HIV and AIDS population over a period of time. We observed that there is a critical threshold parameter, R₀, which determines the behavior of the model. If R₀ ≤ 1, there is a unique disease-free equilibrium; if R₀ < 1, the disease dies out; and if R₀ > 1, the disease-free equilibrium is unstable. We also show how a Markov chain Monte Carlo (MCMC) approach could be used as a supplement to forecast the numbers of reported HIV and AIDS cases. An approach using a Monte Carlo analysis is illustrated to understand the impact of model-based predictions in light of uncertain parameters on the spread of HIV. Finally, to examine this framework and demonstrate how it works, a case study was performed of reported HIV and AIDS cases from an annual data set in Malaysia, and then we compared how these approaches complement each other. We conclude that HIV disease in Malaysia shows epidemic behavior, especially in the context of understanding and predicting emerging cases of HIV and AIDS.

Commercial sex behaviours among involuntary male bachelors: findings from a survey of migrants in Xi'an, China

BACKGROUND

The highly male-biased sex ratio at birth has produced a severe male 'marriage squeeze' in China. However, with an imbalanced sex ratio, the marriage-squeezed or involuntary bachelors can meet their sexual needs only through ways other than marriage.

METHODS

To investigate the commercial sex behaviours of involuntary bachelors, we conducted a survey on reproductive health and family living among male migrant bachelors in Xi'an City, the capital of Shaanxi Province, from December 2009 to January 2010.

RESULTS

The prevalence of commercial sex use was 37.2% among unmarried men, 30.1% among married but separated men and 17.2% among married and cohabitating men (χ(2) = 31.33; P = 0.000; df = 2). Marital status, knowledge about acquired immunodeficiency syndrome (AIDS), age and income were associated with the prevalence and frequency of commercial sex behaviours. Condom use was less frequent among involuntary bachelors and was significantly associated with knowledge about AIDS and other sexually transmitted diseases, the frequency of commercial sex behaviours, marital status and age.

CONCLUSIONS

The higher prevalence of commercial sex behaviours and the lower frequency of condom use indicate a higher risk of disease from commercial sex among involuntary bachelors, implicating both individual and public health.

Challenges to recruiting population representative samples of female sex workers in China using Respondent Driven Sampling

We explore the network coverage of a sample of female sex workers (FSWs) in China recruited through Respondent Drive Sampling (RDS) as part of an effort to evaluate the claim of RDS of population representation with empirical data. We take advantage of unique information on the social networks of FSWs obtained from two overlapping studies--RDS and a venue-based sampling approach (PLACE)--and use an exponential random graph modeling (ERGM) framework from local networks to construct a likely network from which our observed RDS sample is drawn. We then run recruitment chains over this simulated network to assess the assumption that the RDS chain referral process samples participants in proportion to their degree and the extent to which RDS satisfactorily covers certain parts of the network. We find evidence that, contrary to assumptions, RDS oversamples low degree nodes and geographically central areas of the network. Unlike previous evaluations of RDS which have explored the performance of RDS sampling chains on a non-hidden population, or the performance of simulated chains over previously mapped realistic social networks, our study provides a robust, empirically grounded evaluation of the performance of RDS chains on a real-world hidden population.

An Empirical Analysis of the Impact of Recruitment Patterns on RDS Estimates among a Socially Ordered Population of Female Sex Workers in China

Respondent-driven sampling (RDS) is a method for recruiting "hidden" populations through a network-based, chain and peer referral process. RDS recruits hidden populations more effectively than other sampling methods and promises to generate unbiased estimates of their characteristics. RDS's faithful representation of hidden populations relies on the validity of core assumptions regarding the unobserved referral process. With empirical recruitment data from an RDS study of female sex workers (FSWs) in Shanghai, we assess the RDS assumption that participants recruit nonpreferentially from among their network alters. We also present a bootstrap method for constructing the confidence intervals around RDS estimates. This approach uniquely incorporates real-world features of the population under study (e.g., the sample's observed branching structure). We then extend this approach to approximate the distribution of RDS estimates under various peer recruitment scenarios consistent with the data as a means to quantify the impact of recruitment bias and of rejection bias on the RDS estimates. We find that the hierarchical social organization of FSWs leads to recruitment biases by constraining RDS recruitment across social classes and introducing bias in the RDS estimates.

Same-Sex Sexual Behaviors Among Male Migrants in a Context of Male “Marriage Squeeze”

The male marriage squeeze in China may increase the prevalence of male same-sex sexual behaviors among unmarried male migrants who lack stable female sexual partners. The same-sex sexual behaviors among unmarried male migrants appear to be at high risk of transmission of human immunodeficiency virus (HIV) and sexually transmitted infections (STIs), mainly because of a lack of knowledge of these diseases. Using data from the “Survey on Reproductive Health and Family Life of Migrant Male Bachelors in Urban Areas” conducted in Xi’an City, Shaanxi Province, in December 2009 and January 2010, this study compares same-sex sexual behaviors of unmarried with that of married male migrants (including married but separated men who are migrating without their spouse or partner and cohabitating men who are migrating with their spouse or partner). It is reported that the prevalence of same-sex sexual behaviors among unmarried males reaches 11%, more than twice the 5.1% reported by married but separated men and thrice the 3.8% reported by cohabitating men. It also appears that the same-sex sexual behaviors is significantly associated with men’s attitudes toward same-sex sexual behaviors (odds ratio = 1.59, p < .001), toward life-long bachelorhood (odds ratio = 1.35, p < .01), and with marital status (odds ratio = 0.37, p < .01). The frequency of condom use appears to be higher among unmarried men than among men who are married, whether or not they migrated with their wives, and is significantly associated with scores on knowledge about HIV/AIDS (estimated coefficient = .12, p < .001) and STIs (estimated coefficient = .22, p < .01). It is also associated with the likelihood of same-sex sexual behaviors (estimated coefficients = .83, p < .01) and marital status (estimated coefficients for married but separated = −.50, p < .05; estimated coefficients for cohabitating = −.77, p < .001).

The relationship history calendar: improving the scope and quality of data on youth sexual behavior

Most survey data on sexual activities are obtained via face-to-face interviews, which are prone to misreporting of socially unacceptable behaviors. Demographers have developed various private response methods to minimize social desirability bias and improve the quality of reporting; however, these methods often limit the complexity of information collected. We designed a life history calendar-the Relationship History Calendar (RHC)-to increase the scope of data collected on sexual relationships and behavior while enhancing their quality. The RHC records detailed, 10-year retrospective information on sexual relationship histories. The structure and interview procedure draw on qualitative techniques, which could reduce social desirability bias. We compare the quality of data collected with the RHC with a standard face-to-face survey instrument through a field experiment conducted among 1,275 youth in Kisumu, Kenya. The results suggest that the RHC reduces social desirability bias and improves reporting on multiple measures, including higher rates of abstinence among males and multiple recent sexual partnerships among females. The RHC fosters higher levels of rapport and respondent enjoyment, which appear to be the mechanisms through which social desirability bias is minimized. The RHC is an excellent alternative to private response methods and could potentially be adapted for large-scale surveys.

Mate Availability and Women's Sexual Experiences in China

Data from the 1999-2000 Chinese Health and Family Life Survey were merged with community-level data from the 1982, 1990, and 2000 Chinese censuses to examine the relationship between the local sex ratio (number of men per 100 women) and sexual outcomes among women (N = 1,369). Consistent with hypotheses derived from demographic-opportunity theory, multilevel logistic regression analyses showed that women are more likely to be sexually active, to have had premarital sexual intercourse, to have been forced to have sex, and to test positive for a sexually transmitted infection when there is a relative abundance of age-matched men in their local community. Education, birth cohort, and geographic location also emerged as significant predictors of women's sexual experiences.

On Same-Sex Sexual Behaviors Among Male Bachelors in Rural China

Using data from a survey conducted in the rural areas of Anhui Province, this study adopted the crosstabs and logistic regression model to analyze the same-sex sexual behaviors of forced male bachelors and the determinants when compared with married men with same ages. The prevalence of same-sex sexual behaviors among the unmarried men was reported as 17.2%, significantly higher than 8.9% among married men with same ages, indicating that same-sex sexual behaviors could be as a compensation for the absence of female sexual partners to some extent for those marriage squeezed or forced male bachelors. Among all groups, the occurrence of unprotected sexual behaviors were reported above 60%, regardless of marital status and the genders of sexual partners; the scores obtained on knowledge of acquired immune deficiency syndrome (AIDS) and sexually transmitted diseases (STDs) among bachelors (AIDS knowledge = 2.85; STDs knowledge = 2.38) are much poorer than those of married men (AIDS knowledge = 3.45; STDs knowledge = 2.79), which might exert potential negative impacts on men’s health.

Imbalanced sex ratios, men's sexual behavior, and risk of sexually transmitted infection in China

China has been experiencing pronounced changes in its sex ratio, but little research has explored the consequences of these changes for sexual behavior and health. We merge data from the 1999-2000 Chinese Health and Family Life Survey with community-level data from the 1982, 1990, and 2000 Chinese censuses to examine the relationship between the local sex ratio and several dimensions of men's sexual behavior and sexual health. Multilevel logistic regression models show that, when faced with a relative abundance of age-matched women in their community, Chinese men are slightly less likely to have intercourse with commercial sex workers, but are more likely to engage in premarital noncommercial intercourse and to test positive for a sexually transmitted infection. These findings are consistent with hypotheses derived from demographic-opportunity theory, which suggests that an abundance of opposite-sex partners will increase the risk of early, frequent, and multi-partner sex and, through this, sexually transmitted infection risk.

Social influence and individual risk factors of HIV unsafe sex among female entertainment workers in China

Female entertainment workers in China are at increased sexual risk of HIV, but causes of their unprotected sex remain poorly understood. We develop a model that integrates information-motivation-behavioral skills (IMB) with social influences and test the model in a venue-based sample of 732 female entertainment workers in Shanghai. Most IMB and social influence measures are statistically significant in bivariate relationships to condom use; only HIV prevention motivation and behavioral self-efficacy remain significant in the multiple regressions. Self-efficacy in condom use is the most proximate correlate, mediating the relationship between information and motivation and condom use. Both peer and venue supports are important, but their influences over condom use are indirect and mediated through prevention motivation and/or self-efficacy. Behavioral intervention is urgently needed and should take a multilevel approach, emphasizing behavioral skills training and promoting a supportive social/working environment.

Causes and consequences of increasing club drug use in China: a descriptive assessment

Club drugs have quickly become the most widespread "drugs of abuse" in China. Using data from a convenience sample of 730 club drug users in Shanghai in 2006 , we explored the causes and consequences of club drug use. Descriptive analyses suggest that club drug use is typically polydrug use. Polydrug use is strongly associated with weakened social control, drug use social influences, and a sensation-seeking personality; in addition, it is associated with more negative health and social consequences. Both polydrug and single-club-drug users are at high risk of sexually acquiring and/or transmitting HIV. The study's limitations are noted, and future research is suggested.

HIV transmission networks

PURPOSE OF REVIEW

Over the past several years, one segment of the complex field of HIV transmission dynamics - heterosexual networks - has dominated theoretical and empirical investigation. This review provides an overview of recent work on HIV risks and networks, with a focus on recent findings in heterosexual network dynamics.

RECENT FINDINGS

Qualitative (ethnographic) assessments have demonstrated the heterogeneity and complexity of heterosexual connections, particularly in Africa, where tradition, official polygamy, and unofficial multiperson arrangements have lead to concurrency of sexual partnerships. A large, quantitative study on Likoma Island, Malawi, demonstrated the considerable, interlocking sexual connections that arise from a high-concurrency sexual setting, even with a low average number of partnerships (low degree) of long duration. Such settings, as suggested by ethnographic studies, may be common in Africa and, coupled with newer information about transmissibility during acute and early infection, may provide a plausible explanation for endemic transmission and possibly for rapid HIV propagation.

SUMMARY

Recognition of high-concurrency, low-degree networks is an important development for understanding HIV transmission dynamics. Their relevance to heterosexual transmission, and possible extension to other epidemiologic settings, reinforces the heterogeneity and complexity of HIV transmission dynamics.

Heterogeneous condom use in contemporary Russia

Using data from a panel survey of a representative probability sample of Russian households, we examine how individual traits, locality, and "sex-event context" are associated with condom use in contemporary Russia. At the individual level, age has negative effects and measures of risk orientation have positive effects on the probability of condom use; for women, education has positive effects and Muslim belief has negative effects. Condom use is higher among residents in Moscow and St. Petersburg and lower (for women) among rural residents. Most importantly, the same individuals make different choices about condom use from one sex event to the next, and their choices are systematically related to the nature and duration of their relationship to their partner, as well as to their partner's age. Condom use is prevalent in casual encounters and in those involving new partners or commercial sex workers. Coupled with the strong effects of age for both partners, this pattern represents good news regarding the potential for the spread of HIV in Russia. Other findings are more worrisome: HIV awareness and knowledge of condom's effectiveness in blocking transmission of the virus do not influence condom use at all, and married people are relatively unlikely to use condoms even in extramarital encounters and especially in long-term affairs. Accordingly, interventions should target older Russians who are married and have sex with long-term nonspousal partners.

Heterosexual behavior patterns and the spread of HIV/AIDS: the interacting effects of rate of partner change and sexual mixing

OBJECTIVES

This study evaluates whether the influence of sexual mixing patterns on the human immunodeficiency virus (HIV) epidemic curve is sensitive to the prevailing rates of sexual partner change in a population.

STUDY DESIGN

A biobehavioral macrosimulation model is employed to assess the interacting dynamics of the rates of sexual partner change and patterns of sexual mixing between population subgroups. HIV spread is simulated under 2 rates of partner change scenarios and under various degrees of assortativeness in sexual mixing patterns.

RESULTS

With high rates of partner change, disassortativeness in sexual mixing tends to increase the overall size of the HIV epidemic. However, when relatively low rates of partner change are simulated, disassortative mixing yields a smaller epidemic. This pattern is further influenced by the underlying sexual transmission probabilities of HIV.

CONCLUSIONS

Each of the various determinants of the sexual spread of HIV must not be considered in isolation. Instead, the interactive nature of those determinants should be accounted for in discussions of HIV epidemic dynamics.