Sexual role and transmission of HIV Type 1 among men who have sex with men, in Peru

Comparison of human immunodeficiency virus-related risky sexual behaviors between men who have sex with men only and men who have sex with men and women: A cross-sectional study in Eastern China

Background

Men who have sex with men (MSM) are a significant population contributing to human immunodeficiency virus (HIV) transmission. Nevertheless, few studies have focused on the heterogeneity in MSM. The characteristics of men who have sex with men and women (MSMW) may differ from men who have sex with men only (MSMO).

Methods

From October 2022 to March 2023, a cross-sectional study for MSM was conducted in Eastern China. An electronic questionnaire was used to collect the demographic characteristics and sexual behaviors of participants. A multivariable logistic regression model was used to assess the differences in HIV-related risky sexual behaviors between MSMO and MSMW.

Results

A total of 1993 MSM were enrolled in the study, with 1221 MSMO and 772 MSMW. Compared to MSMW, MSMO reported younger age at first anal sex, higher coerced homosexual experiences, and observed different characteristics of sexual behavior in the past six months. Multivariable analysis indicated that MSMW were more likely to seek casual partners and use stimulants online and offline. MSMW showed inconsistent condom use with online partners (aOR = 0.51, 95 %CI: 0.38-0.68) and more frequent anal sex after drinking (aOR = 2.27, 95 %CI: 1.54-3.35). They also had higher risks of commercial (aOR = 2.47, 95 %CI: 1.71-3.57) and group sexual behaviors (aOR = 1.88, 95 %CI: 1.24-2.83) compared to MSMO.

Conclusion

Our findings suggest that the differential factors may lead MSMW to become a subgroup at high risk of HIV infection. The gender identity and sexual orientation within MSM should be considered when formulating acquired immune deficiency syndrome (AIDS) prevention and control strategies.

Anal Sexual Roles and Impacts on HIV Infection and Psychological Distress Among Men Who Have Sex With Men in China: A 14-Year Longitudinal Study

Previous studies have shown that men who have sex with men (MSM) with different anal sexual roles, namely bottom, versatile, and top, are at different risk of HIV infection and psychological distress. However, the evidence was primarily derived from cross-sectional designs from Western countries, and it remains unclear how anal sexual roles change over a long time and their health impacts among MSM from Eastern countries. We aimed to describe the changes in anal sexual roles among a Chinese sample of MSM over 14 years and explore their effects on HIV infection, depression, anxiety, and suicidal ideation. Between 2009 and 2023, a longitudinal study was conducted on 373 MSM in Changsha, China, to assess their anal sexual roles, HIV infection, and psychological distress, including depression, anxiety, and suicidal ideation. Generalized linear models with a binomial probability was used to analyze the predictive effect of anal sexual roles on HIV infection and psychological distress. At baseline, 30.3% of MSM self-identified as bottom, 32.2% as versatile, and 37.5% as top, and these numbers changed slightly to 35.9%, 33.0%, and 31.1%, respectively, at follow-up (p = 0.131). From baseline to follow-up, 48 (12.9%) new HIV cases were identified. The prevalence of depression increased from 23.1 to 38.1% (p < 0.001), anxiety increased from 25.5% to 35.4% (p = 0.003), and suicidal ideation increased from 30.8 to 38.9% (p = 0.021). MSM with bottom and versatile roles were more likely to have HIV infection, depression, anxiety, and suicidal ideation than those with top roles. MSM's risk of HIV infection and psychological distress varies according to their anal sexual roles, suggesting that future HIV prevention and mental health improvement programs for MSM may benefit from providing targeted and individualized support based on their anal sexual roles, with a particular focus on those with bottom and versatile roles.

Sexual network characteristics, condomless anal intercourse, and the HIV care cascade among MSM living with controlled versus uncontrolled HIV infection in Lima, Peru: a population-based cross-sectional analysis

Background

Despite high rates of HIV transmission among men who have sex with men (MSM) in Lima, Peru, limited data exist on the sexual network characteristics or risk factors for secondary HIV transmission among MSM with uncontrolled HIV infection. We report the frequency of serodiscordant, condomless anal intercourse (CAI) and associated sexual network characteristics among MSM in Lima with detectable HIV viremia and compare to those with undetectable viremia.

Methods

This cross-sectional analysis includes MSM who tested positive for HIV-1 during screening for a trial of partner management and STI control (June 2022-January 2023). Participants were tested for HIV, gonorrhoea, chlamydia, and syphilis, and completed questionnaires on their demographic characteristics, sexual identity and behaviour, sexual network structures and engagement in HIV care.

Findings

Of 665 MSM, 153 (23%) had detectable (>200 copies/mL) viremia. 75% (499/662) of men living with HIV were previously diagnosed, with 94% (n = 469/499) reporting that they were on ART, and 93% (n = 436/469) virally suppressed. 96% (n = 147/153) of men with detectable viremia reported serodiscordant CAI with at least one of their last three sexual partners, and 74% (n = 106/144) reported the same with all three of their recent partners. In contrast, 62% (n = 302/489) of men with undetectable viral load reported serodiscordant CAI with all of their last three partners (p < 0.01).

Interpretation

23% of men living with HIV in Peru had detectable viremia, of whom almost all (96%) reported recent serodiscordant CAI. The primary gap in the HIV care cascade lies in awareness of HIV serostatus, suggesting that improved access to HIV testing could be a key prevention strategy in Peru.

Funding

Funding for this study was provided by NIH/NIMH grants R01 MH118973 (PI: Clark) and R25 MH087222 (PI: Clark).

Exploring Contextual Differences for Sexual Role Strain Among Transgender Women and Men Who Have Sex with Men in Lima, Peru

Sexual and gender politics inform relational expectations surrounding sexual experiences of Peruvian transgender women (TW) and men who have sex with men (MSM). We used the framework of sexual role strain, or incongruence between preferred sexual role and actual sexual practices, to explore potential conflicts between personally articulated identities and externally defined norms of gender and sexuality and its potential to increase HIV/STI risk. Cross-sectional individual- and dyad-level data from 766 TW and MSM in Lima, Peru were used to assess the partnership contexts within which insertive anal intercourse was practiced despite receptive role preference (receptive role strain), and receptive anal intercourse practiced despite insertive role preference (insertive role strain). Sexual role strain for TW was more common with non-primary partners, while for MSM it occurred more frequently in the context of a primary partnership. Receptive role strain was more prevalent for TW with unknown HIV status (reference: without HIV) or pre-sex drug use (reference: no pre-sex drug use). For homosexual MSM, receptive role strain was more prevalent during condomless anal intercourse (reference: condom-protected) and with receptive or versatile partners (reference: insertive). Among heterosexual or bisexual MSM, insertive role strain was more prevalent with insertive or versatile partners (reference: receptive), and less prevalent with casual partners (reference: primary). Our findings suggest TW and MSM experience different vulnerabilities during sexual role negotiation with different partner-types. Future studies should explore the impact of sexual role strain on condom use agency, HIV/STI risk, and discordances between public and private presentations of gender and sexual orientation.

Risk Behaviors Associated with Patterns of Sexualized Stimulant and Alcohol Use among Men Who Have Sex with Men: a Latent Class Analysis

Substance use during sexual encounters (sexualized substance use) is an important driver of HIV and sexually transmitted infection (STI) disparities that are experienced by men who have sex with men (MSM). This analysis aimed to identify patterns of sexualized substance use and their associations with HIV risk behaviors. We utilized visit-level data from a longitudinal cohort of predominantly Black/Latinx MSM, half with HIV and half with substance use in Los Angeles, California. Every 6 months from 8/2014 to 3/2020, participants underwent STI testing and completed surveys on demographics, sexualized substance use (stimulant and/or alcohol intoxication during oral sex, receptive anal intercourse [RAI] and/or insertive anal intercourse [IAI]), transactional sex, biomedical HIV prevention (pre-/post-exposure prophylaxis use or undetectable viral load), and depressive symptoms. Latent class analysis was used to identify patterns of sexualized substance use. Multinomial logit models evaluated risk behaviors associated with latent classes. Among 2386 study visits from 540 participants, 5 classes were identified: no substance use, sexualized stimulant use, sexualized alcohol use, sexualized stimulant and alcohol use, and stimulant/alcohol use during oral sex and RAI. Compared to the no sexualized substance use class, sexualized stimulant use was associated with transactional sex, current diagnosis of STIs, not using HIV biomedical prevention, and depressive symptoms. Sexualized alcohol use had fewer associations with HIV risk behaviors. Patterns of sexual activities, and the substances that are used during those activities, confer different risk behavior profiles for HIV/STI transmission and demonstrate the potential utility of interventions that combine substance use treatment with HIV prevention.

Longitudinal Event-Level Analysis of Gay and Bisexual Men's Anal Sex Versatility: Behavior, Roles, and Substance Use

Gay and bisexual Men Who Have Sex with Men (GBM) are sexually unique in that they can practice penile-anal sex versatility, i.e. engage in insertive and receptive anal sex. Individual-level versatility is extensively researched both as a sexual behavior linked to HIV/STI transmission, and as a GBM identity that can change over time. However, there is a dearth of research on event-level versatility (ELV), defined as taking the receptive and insertive role in the same sexual encounter. We analyzed event-level data from 644 GBM in the Momentum Health Study from February 2012-February 2017 to identify factors associated with ELV prevalence, the relationship between ELV and anal sex role preference, and sero-adaptive and sexualized drug use strategies. Univariate analysis revealed ELV prevalence rates between 15% and 20%. A multivariate generalized linear mixed model indicated ELV significantly (p < .05) associated with versatile role preference and condomless sex. However, the majority of ELV came from GBM reporting insertive or receptive role preferences, and there was significantly higher condom use among sero-discordant partners, indicating sero-adaptation. Multivariate log-linear modeling identified multiple polysubstance combinations significantly associated with ELV. Results provide insights into GBM sexual behavior and constitute empirical data useful for future HIV/STI transmission pattern modeling.

The Law and Economics of Grindr: A Response to Carson

In the Winter 2017 edition of JLME, Dr. Carson outlined an economic approach to the epidemiology of HIV transmission within the gay community, with a special emphasis on mobile apps. His conclusion is that HIV transmission amongst the gay community constitutes a collective action problem, which is resolved by the social norm of using a condom. This article critiques Dr. Carson's approach from an economic perspective. By utilizing classic law and economic theory, this article will argue that HIV transmission may not, in fact, constitute a collective action problem in economic terms, and that instead condom use as a method of disease protection in theory can arise from purely rational, market driven actions. To do so, it borrows from transactional theory of information asymmetry to show the potential to alert counterparts as to serostatus. This conclusion provides an important supplement to Carson: rather than social norms being the core driver in condom usage to prevent HIV, instead condom use may arise solely as a result of rational, private decision making arising from market signaling. The article then critiques its own findings to demonstrate that it is unclear whether Carson's argument or the argument in this paper is, indeed, correct - which may represent a limitation in the analytical techniques advanced.

Sexual network characteristics of men who have sex with men with syphilis and/or gonorrhoea/chlamydia in Lima, Peru: network patterns as roadmaps for STI prevention interventions

OBJECTIVE

While men who have sex with men (MSM) are disproportionately affected by Peru's overlapping HIV and STI epidemics, there are few data on how partnership-level and network-level factors affect STI transmission in Peru. We explored partnership-level and network-level factors associated with gonorrhoea/chlamydia (Neisseria gonorrhoeae and/or Chlamydia trachomatis (NG/CT)) and/or syphilis infection among MSM in Peru.

METHODS

We present the results of a cross-sectional secondary analysis of MSM (n=898) tested for syphilis and NG/CT infection as part of the screening process for two STI control trials in Lima, Peru. Participants completed questionnaires on demographics, sexual identity and role, characteristics of their three most recent sexual partners (partner sexual orientation, gender, role, partnership type, partner-specific sexual acts) and 30-day sexual network characteristics (number of sexual partners, partnership types, frequency of anal/vaginal intercourse). Participants were tested for syphilis and urethral, rectal and oropharyngeal NG/CT. Differences in network characteristics were analysed with χ2 and Kruskal-Wallis tests.

RESULTS

Approximately 38.9% of participants had a new STI diagnosis (syphilis (rapid plasma reagin ≥16): 10.6%; NG/CT: 22.9%; syphilis-NG/CT coinfection: 5.4%). Condomless anal intercourse (CAI) was not significantly associated with an STI diagnosis. Gay-identified participants with exclusively homosexual networks had a higher prevalence of STIs (47.4%) than gay-identified MSM with only heterosexual/bisexual partners (34.6%, p=0.04), despite reporting fewer sexual partners (any partners: 2, 1-4 vs 3, 2-6; p=0.001; casual partners: 1, 0-3 vs 2, 1-4; p=0.001) and more stable partnerships (1, 0-1 vs 0, 0-1; p=0.003) in the last month.

CONCLUSIONS

Network size and the number of casual sexual partners were associated with NG/CT infection among MSM in Peru. Despite reporting fewer sexual risk behaviours (smaller network size, more stable partnerships, less CAI), MSM with homosexual-only sexual networks had a higher prevalence of NG/CT and syphilis. These findings suggest network composition among MSM in Peru plays an important role in the risk for STI acquisition.

On how role versatility boosts an STI

The prevalence of the HIV-1 infection has decayed in the last decades in western heterosexual populations. However, among men who have sex with men (MSM) the prevalence is still high, despite intensive campaigns and treatment programs that keep infected men as undetectable (Beyrer et al. 2012). Promiscuity and condom fatigue (Adam et al. 2005), which are not unique to the MSM community, are making unprotected anal intercourse (UAI) more common and sexually transmitted infections (STIs) presumably harder to track. Yet, MSM communities are peculiar in the sense that men can adopt fixed (insertive or receptive) or versatile (both practices) roles. Some old theoretical work (Wiley & Herschkorn 1989, Van Druten et al. 1992, Trichopoulos et al. 1998) predicted that the transmission of HIV-1 would be enhanced in MSM populations engaged more in role versatility than in role segregation, in which fixed roles are predominantly adopted. These predictions were based on the assumption that the probability of acquisition from unprotected insertive anal (UIA) sex was neglectable. However, as later shown (Vittinghoff et al. 1999, Goodreau et al. 2005), this assumption is inappropriate and HIV-1 may still be acquired via UIA sex. Here I show through a stochastic model that the increase of the HIV-1 prevalence among MSM due to role versatility holds under a stronger assumption of bidirectional virus transmission.

HPV knowledge, burden and genital wart location among heterosexually identified versus homosexually identified men who have sex with men in Lima, Peru: cross-sectional results from a cohort study

OBJECTIVES

The relationship between sexual practices, identity and role among Latino men who have sex with men (MSM) and HIV risk is the subject of ongoing investigation but less is known about how these aspects of sexuality relate to human papilloma-virus (HPV), an independent risk factor for HIV. This observational study investigated the relationship between HPV and sexual practices, identity and role as well as other sexually transmitted infection (STI)/HIV risk factors among HIV-negative heterosexually and homosexually identified Peruvian MSM.

SETTING

Community-based clinic for MSM in Lima, Peru.

PARTICIPANTS

756 subjects were screened based on inclusion criteria of: born anatomically male; age ≥18 years; had any anal intercourse with a man during the previous 12 months; residing in metropolitan Lima; HIV negative; willing to commit to twice-yearly clinic visits for 24 months; had not participated in an HIV or HPV vaccine study. 600/756 participants met the inclusion criteria and were enrolled, of whom 48% (284) identified as homosexual and 10% (57) as heterosexual, the basis of the analyses performed.

RESULTS

Compared with homosexually identified MSM, heterosexually identified MSM had completed fewer years of formal education and were less likely to have: anogenital HPV or visible anal warts; given oral sex to a man; or used a condom with their most recent female sexual partner (all p<0.05). Conversely, heterosexually identified MSM were more likely to have: visible penile warts; used a condom during last anal intercourse; smoked cigarettes; had transactional sex; and used drugs during sex in the previous month (all p<0.01). There was no difference found between heterosexually and homosexually identified MSM by syphilis or high-risk HPV prevalence.

CONCLUSIONS

HPV burden, wart type (penile vs anal) and select HIV/STI risk behaviours differed between heterosexually and homosexually identified Peruvian MSM. Understanding the implications of these differences can lead to tailored HIV/STI prevention interventions for heterosexually identified MSM.

TRIAL REGISTRATION NUMBER

NCT01387412.

Partner-Level Factors Associated with Insertive and Receptive Condomless Anal Intercourse Among Transgender Women in Lima, Peru

Condomless anal intercourse among transgender women (TW) in Peru has been shown to vary by the type of partner involved (e.g. primary vs. casual vs. transactional sex partner), but no previous studies have explored variations in partner-level patterns of condom use according to type of anal intercourse. We evaluated the relationship between partnership characteristics and condom use during insertive (IAI) versus receptive anal intercourse (RAI) among TW with recent, non-female partners. Condomless IAI was more common with transactional and casual sex partners and by TW who self-reported HIV-uninfected serostatus (p < 0.05), alcohol use disorders, or substance use before sex. Condomless RAI was more common with primary partners and by TW who described their HIV serostatus as unknown (p < 0.05). Examining partner-level differences between condomless IAI and RAI reveals distinct patterns of HIV/STI risk among TW, suggesting a need for HIV prevention strategies tailored to the specific contexts of partners, practices, and networks.

Men Who Have Sex With Men in Peru: Acceptability of Medication-Assisted Therapy for Treating Alcohol Use Disorders

In Peru, the HIV epidemic is concentrated in men who have sex with men (MSM) and transgender women (TGW). Multiple studies correlate alcohol use disorders (AUDs) with risky sexual behaviors among Peruvian MSM. Qualitative research was used to inform a clinical trial on the acceptability of medication-assisted therapies to assist management of AUDs and improve antiretroviral therapy (ART) adherence among MSM/TGW in Peru. Three focus groups involving HIV-infected or HIV-uninfected MSM/TGW ( n = 26) with AUDs (AUDIT ≥ 8) were transcribed, translated from Spanish into English, and analyzed using thematic content analysis. Despite having an AUD, participants considered themselves "social" drinkers, minimized their drinking behaviors, and differed about whether or not alcohol problems could be treated. Participants expressed skepticism about medication for treating AUDs. Three concepts emerged as necessary components of a treatment program for alcohol problems: cost, family support, and the potential to drink less alcohol without attaining total abstinence. This study reveals important areas of education to increase potential acceptability of a medication for treating AUDs among MSM/TGW. Given the social conditions and knowledge base of the participants, medication-assisted therapies using naltrexone may be a beneficial strategy for MSM with AUDs.

Influence of concurrency, partner choice, and viral suppression on racial disparity in the prevalence of HIV infected women

In 1992, Watts and May introduced a simple dynamical systems model of the spread of HIV based on disease transmission per partnership including the length of partnership duration. This model allowed for the treatment of concurrent partnerships, although it was hampered by the assumption of an important latent phase which generated a non-autonomous system. Subsequent models including concurrency have been based on networks, Monte Carlo, and stochastic simulations which lose a qualitative understanding of the effects of concurrency. We present a new autonomous deterministic model of the effect of concurrent sexual partnerships that allows for an analytical study of disease transmission. We incorporate the effect of concurrency through the newly derived force of infection term in a mathematical model of the transmission of HIV through sexual contact in a population stratified by sexual behavior and race/ethnicity. The model also includes variations in population mixing (partner choice) and non-uniform Highly Active Anti-Retroviral Treatment (HAART) leading to viral suppression. We use this mathematical model to understand the non-uniform spread of HIV in women who were infected through heterosexual contact. In addition, an analytical study shows the importance of continued condom use in virally suppressed MSM. Numerical simulations of the reproduction number as a function of concurrency, viral suppression level, and mixing show a reservoir of disease present in both heterosexual and MSM populations. Statistical analysis of parameter values show that viral suppression level, mixing and progression to AIDS without viral suppression have a strong correlation (either positive or negative) with the number of HIV positive women. Concurrency and assortative mixing are shown to be essential to reproduce infection levels in women, as reported by 2010 data from the Center for Disease Control (CDC).

Social Network Analysis in Human Resource Development: A New Methodology

Through an exhaustive review of the literature, this article looks at the applicability of social network analysis (SNA) in the field of humanresource development. The literature review revealed that a number of disciplines have adopted this unique methodology, which has assisted in the development of theory. SNA is a methodology for examining the structure among actors, groups, and organizations and aides in explaining variations in beliefs, behaviors, and outcomes. The article is divided into three main sections: social network theory and analysis, the social network approach and application to HRD. First, the article provides an overview of social network theory and SNA. Second, the process for conducting an SNA is described and third, the application of SNA to the field of HRD is presented. It is proposed that SNA can improve the empirical rigor of HRD theory building in such areas as organizational development, organizational learning, leadership development, organizational change, and training and development.

Prevalence and associated risk characteristics of HIV infection based on anal sexual role among men who have sex with men: a multi-city cross-sectional study in Western China

BACKGROUND

The HIV prevalence among men who have sex with men (MSM) in Western China is substantial and increasing at an alarming rate. The current HIV infection prevalence among MSM in Western China and its associated risk characteristics were explored by looking at different anal sexual roles separately.

METHODS

A total 1245 MSM recruited by convenience sampling from multiple sources and areas in the Chongqing and Sichuan region were interviewed using an anonymous self-administered questionnaire with the assistance of investigators and then underwent HIV testing. Multivariate logistic regression was used to identify factors independently associated with HIV infection.

RESULTS

Of the 1235 respondents who reported their sexual roles during anal sex with men, the overall HIV antibody positive rate was 21.21% (262/1235). With regard to the different anal sex roles, HIV-positive rates were significantly higher among men who played the '0.5' role (versatile, equal) and '0' role (only bottom or versatile, but mostly bottom) during anal sex with men than among those who played the '1' role (only top or versatile, but mostly top) (26.41% for '0.5' role, 26.20% for '0' role, and 15.19% for '1' role; Chi-square=22.66, p<0.0001). Statistically significant differences were not found between the '0.5' role and '0' role groups (p > 0.05). The '1' role MSM who had an education level lower than senior high school, a rural household registration, and low self-perceived severity status of AIDS, the '0.5' role MSM who had an education level lower than senior high school and had not undergone HIV testing in the recent 1 year, and the '0' role MSM who were retired or unemployed and had been diagnosed with a sexually transmitted disease by a doctor in the recent 6 months were more likely to be HIV-infected.

CONCLUSIONS

In this study, the HIV prevalence among MSM was alarmingly high. Moreover, the '0.5' and '0' role MSM were found to have a higher risk of infection compared to the '1' role MSM, while respective risk characteristics were not completely the same across the three groups. Along with routine preventive intervention services, more focused and specific interventions are needed to target anal sex role classes separately.

Gender Expression and Risk of HIV Infection Among Black South African Men Who Have Sex with Men

To explore demographic, behavioral and psychosocial risk factors for HIV infection in South African MSM we recruited 480 MSM (aged 18 and 44 years) using respondent-driven sampling. Data were collected through individual computer-assisted face-to-face interviews. Participants were tested for HIV. RDS-adjusted HIV prevalence is 30.1 % (unadjusted 35.6 %). Few participants had ever engaged in both receptive and insertive anal sex; sex with women was frequently reported. Independent demographic and behavioral correlates of HIV infection include age, education, number of male sexual partners, ever having been forced to have sex, and ever having engaged in transactional sex; engagement in sex with women was a protective factor. Psychosocial risk factors independently associated with HIV infection were feminine identification, internalized homophobia, and hazardous drinking. Our findings confirm what has been found in other studies, but also suggest that the dynamics and context of sexual transmission among MSM in South Africa differ from those among MSM in Western countries.

HIV prevalence, sexual behaviours and engagement in HIV medical care among an online sample of sexually active MSM in Venezuela

In Venezuela, members of a social and sexual partner networking site for men who have sex with men (MSM) completed an online survey regarding sexual behaviours and HIV medical care. Among the 2851 respondents, self-reported HIV prevalence was 6.6%. Of participants living with HIV, 73.2% reported taking antiretroviral medication and 56.6% reported complete adherence within the past month. Participants living with HIV were more likely to be older (aOR = 1.04 per one-year increase in age, 95% CI: 1.02, 1.06) and diagnosed with a sexually transmitted infection in the previous year (aOR 3.26, 95% CI: 2.11, 5.04). These data provide further understanding of the HIV epidemic among MSM in Venezuela, and potential targets for HIV prevention interventions.

Association between sexual role and HIV status among Peruvian men who have sex with men seeking an HIV test: a cross-sectional analysis

In Latin America, sexual role, sexual identity and sexual practices are intricately related; the roles activo, pasivo and moderno often encompass sexual identity and sexual practices. We aimed to understand the association between sexual role and HIV status in Peruvian men who have sex with men. HIV-testing services at Epicentro Salud, a Peruvian gay men's health centre, were paired with clinic data on demographics and sexual behaviour. Bidirectional stepwise logistic regression was conducted to determine associations between sexual role and HIV status. Of 366 clients who underwent HIV testing, 86 (23.5%) tested positive. There was a strong association between sexual role ('activo' or typically insertive, 'pasivo' or typically receptive, 'moderno' or typically versatile) and a positive HIV test (p = 0.002). Compared to clients with an activo role, those who reported a pasivo (OR = 6.14) and moderno (OR = 6.26) role were more likely to test positive for HIV. Sexual role was associated with sexual identity (gay, straight and bisexual) and gender of partners in the past six months. Self-reported pasivo and moderno sexual roles were strongly associated with a positive HIV test result. Further research should examine differences in sexual practices between sexual role groups.

Combination HIV prevention among MSM in South Africa: results from agent-based modeling

HIV prevention trials have demonstrated the effectiveness of a number of behavioral and biomedical interventions. HIV prevention packages are combinations of interventions and offer potential to significantly increase the effectiveness of any single intervention. Estimates of the effectiveness of prevention packages are important for guiding the development of prevention strategies and for characterizing effect sizes before embarking on large scale trials. Unfortunately, most research to date has focused on testing single interventions rather than HIV prevention packages. Here we report the results from agent-based modeling of the effectiveness of HIV prevention packages for men who have sex with men (MSM) in South Africa. We consider packages consisting of four components: antiretroviral therapy for HIV infected persons with CD4 count <350; PrEP for high risk uninfected persons; behavioral interventions to reduce rates of unprotected anal intercourse (UAI); and campaigns to increase HIV testing. We considered 163 HIV prevention packages corresponding to different intensity levels of the four components. We performed 2252 simulation runs of our agent-based model to evaluate those packages. We found that a four component package consisting of a 15% reduction in the rate of UAI, 50% PrEP coverage of high risk uninfected persons, 50% reduction in persons who never test for HIV, and 50% ART coverage over and above persons already receiving ART at baseline, could prevent 33.9% of infections over 5 years (95% confidence interval, 31.5, 36.3). The package components with the largest incremental prevention effects were UAI reduction and PrEP coverage. The impact of increased HIV testing was magnified in the presence of PrEP. We find that HIV prevention packages that include both behavioral and biomedical components can in combination prevent significant numbers of infections with levels of coverage, acceptance and adherence that are potentially achievable among MSM in South Africa.

What can mathematical models tell us about the relationship between circular migrations and HIV transmission dynamics?

Circular migrations are the periodic movement of individuals between multiple locations, observed in parts of sub-Saharan Africa. Relationships between circular migrations and HIV are complex, entailing interactions between migration frequency, partnership structure, and exposure to acute HIV infection. Mathematical modeling is a useful tool for understanding these interactions. Two modeling classes have dominated the HIV epidemiology and policy literature for the last decade: one a form of compartmental models, the other network models. We construct models from each class, using ordinary differential equations and exponential random graph models, respectively. Our analysis suggests that projected HIV prevalence is highly sensitive to the choice of modeling framework. Assuming initial equal HIV prevalence across locations, compartmental models show no association between migration frequency and HIV prevalence or incidence, while network models show that migrations at frequencies shorter than the acute HIV period predict greater HIV incidence and prevalence compared to longer migration periods. These differences are statistically significant when network models are extended to incorporate a requirement for migrant men's multiple partnerships to occur in different locations. In settings with circular migrations, commonly-used forms of compartmental models appear to miss key components of HIV epidemiology stemming from interactions of relational and viral dynamics.

Socialization patterns and their associations with unprotected anal intercourse, HIV, and syphilis among high-risk men who have sex with men and transgender women in Peru

The association of socialization patterns with unprotected anal intercourse (UAI) and HIV/STI prevalence remains underexplored in men who have sex with men (MSM) and transgender women (TW) in developing country settings. We evaluated the correlation of UAI, HIV, and syphilis with MSM/TW venue attendance and social network size among high-risk MSM and TW in Peru according to self-reported sexual identity. Frequency of venue attendance and MSM/TW social network size were lowest among heterosexual MSM and highest among TW respondents. Attendance (frequent or occasional) at MSM/TW venues was associated with increased odds of insertive UAI among heterosexual participants. Frequent venue attendance was associated with increased odds of receptive UAI among gay/homosexual, bisexual, and TW participants. Further investigation of the differing socialization patterns and associations with HIV/STI transmission within subgroups of Peruvian MSM and TW will enable more effective prevention interventions for these populations.

Stochastic variation in network epidemic models: implications for the design of community level HIV prevention trials

Important sources of variation in the spread of HIV in communities arise from overlapping sexual networks and heterogeneity in biological and behavioral risk factors in populations. These sources of variation are not routinely accounted for in the design of HIV prevention trials. In this paper, we use agent-based models to account for these sources of variation. We illustrate the approach with an agent-based model for the spread of HIV infection among men who have sex with men in South Africa. We find that traditional sample size approaches that rely on binomial (or Poisson) models are inadequate and can lead to underpowered studies. We develop sample size and power formulas for community randomized trials that incorporate estimates of variation determined from agent-based models. We conclude that agent-based models offer a useful tool in the design of HIV prevention trials.

Can male circumcision have an impact on the HIV epidemic in men who have sex with men?

BACKGROUND

Three trials have demonstrated the prophylactic effect of male circumcision (MC) for HIV acquisition among heterosexuals, and MC interventions are underway throughout sub-Saharan Africa. Similar efforts for men who have sex with men (MSM) are stymied by the potential for circumcised MSM to acquire HIV easily through receptive sex and transmit easily through insertive sex. Existing work suggests that MC for MSM should reach its maximum potential in settings where sexual role segregation is historically high and relatively stable across the lifecourse; HIV incidence among MSM is high; reported willingness for prophylactic circumcision is high; and pre-existing circumcision rates are low. We aim to identify the likely public health impact that MC interventions among MSM would have in one setting that fulfills these conditions-Peru-as a theoretical upper bound for their effectiveness among MSM generally.

METHODS AND FINDINGS

We use a dynamic, stochastic sexual network model based in exponential-family random graph modeling and parameterized from multiple behavioral surveys of Peruvian MSM. We consider three enrollment criteria (insertive during 100%, >80% or >60% of UAI) and two levels of uptake (25% and 50% of eligible men); we explore sexual role proportions from two studies and different frequencies of switching among role categories. Each scenario is simulated 10 times. We estimate that efficiency could reach one case averted per 6 circumcisions. However, the population-level impact of an optimistic MSM-MC intervention in this setting would likely be at most ∼5-10% incidence and prevalence reductions over 25 years.

CONCLUSIONS

Roll-out of MC for MSM in Peru would not result in a substantial reduction in new HIV infections, despite characteristics in this population that could maximize such effects. Additional studies are needed to confirm these results for other MSM populations, and providers may consider the individual health benefits of offering MC to their MSM patients.

Who mixes with whom among men who have sex with men? Implications for modelling the HIV epidemic in southern India

In India, the identity of men who have sex with men (MSM) is closely related to the role taken in anal sex (insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role segregation (taking only the insertive or receptive role) and the extent of assortative (within-group) mixing are known to affect HIV epidemic size in other settings and populations. This study explores how different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India, affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to disassortative (minimising within-group mixing). A simple model was used to obtain insights into the relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore. With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were seen between the fits identified using different mixing scenarios, but little difference was projected in future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled, targeted at the different identity groups. For intervention strategies targeting the receptive or receptive and versatile MSM together, the overall impact was very similar for different mixing patterns. However, for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for different mixing scenarios; more impact was achieved with greater levels of disassortative mixing.

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Different mixing scenarios are explored for 3 groups of role-segregated MSM.

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Models show that the mixing scenario affects both R₀ and endemic HIV prevalence.

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When models are fit to data, predicted HIV trends are unaffected by mixing.

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Impact of targeted (but not non-targeted) interventions can be affected by mixing.

Identifying risk: a comparison of risk between heterosexual-identifying bisexual men and other bisexual men in Vientiane, Laos

Men who have sex with men are a priority population for HIV control in Laos, but encompass men diverse in sexual orientation, gender identification, and behavior. Behaviorally bisexual men and their sexual partners were recruited in Vientiane, Laos, in 2010 using modified snowball sampling. Heterosexual-identifying bisexual men identified as exclusively/predominantly heterosexual and other bisexual men identified as bisexual or predominantly/exclusively homosexual. Sixty (68%) heterosexual-identifying and 38 (32%) other bisexual men were recruited; the median number of sex partners in the past year was eight and seven, respectively. Consistent condom use was low with regular (7%) and casual (35%) partners and did not differ by identity. More heterosexual-identifying (53%) than other bisexual (29%) men reported weekly alcohol consumption. Twelve (20%) heterosexual-identifying and 15 (54%) other bisexual men correctly answered all HIV-knowledge questions. High-risk behaviors for STI and HIV transmission were common. Targeted HIV prevention initiatives are needed, particularly to reach heterosexual-identifying bisexual men.

Anal sex role segregation and versatility among men who have sex with men: EXPLORE Study

Anal sex role patterns and correlates during unprotected anal sex were examined longitudinally among HIV-negative men who have sex with men. Nearly 9.6% were exclusively receptive, 16.7% exclusively insertive, and 63.0% versatile. Versatility was more likely with primary and HIV-negative/unknown status partners and among younger men and substance users but less likely among Blacks and with higher number of partners. Exclusively receptive role was more likely with HIV-negative/unknown status partners and among younger men and substance users but less likely with higher number of partners. Examining anal sex role patterns helps understand the factors that drive the epidemic among men who have sex with men.

An exploration of elevated HIV and STI risk among male sex workers from India

Background

Men who have sex with men (MSM) who also report transactional sex (male sex workers or MSWs) are known to be at higher risk for HIV and sexually transmitted infections (STIs). The study aimed to profile socio-demographic characteristics and risk factors associated with high HIV prevalence among MSWs.

Methods

A cross-sectional study was conducted in 2008–9 among 483 high-risk MSM who attended STI clinics at Mumbai and Hyderabad, two large cities in India.

Results

About 70% of the MSM reported transactional sex. As compared to other MSM, MSWs had more male partners (8.9 versus 2.5, p < 0.001) and higher rates of receptive anal sex (96% versus 72%, p < 0.001). HIV prevalence among MSWs and other MSM was 43.6% and 18.1% respectively. HIV prevalence among MSWs was associated with the place of residence (MSWs from Hyderabad were 7.3 times more likely to be infected), positive syphilis serology (3.8 times) and duration of sex work (increased by 8% for every additional year).

Conclusion

The study showed that MSWs are at high risk for HIV acquisition/transmission, which highlights the need for intensified interventions for personalized risk-reduction counselling and STI screening. Newer biomedical interventions such as pre-exposure prophylaxis and treatment as prevention could also be considered.

Sex role segregation and mixing among men who have sex with men: implications for biomedical HIV prevention interventions

OBJECTIVE

Men who have sex with men (MSM) practice role segregation - insertive or receptive only sex positions instead of a versatile role - in several international settings where candidate biomedical HIV prevention interventions (e.g., circumcision, anal microbicide) will be tested. The effects of these position-specific interventions on HIV incidence are modeled.

MATERIALS AND METHODS

We developed a deterministic compartmental model to predict HIV incidence among Indian MSM using data from 2003-2010. The model's sex mixing matrix was derived from network data of Indian MSM (n=4604). Our model captures changing distribution of sex roles over time. We modeled microbicide and circumcision efficacy on trials with heterosexuals.

RESULTS

Increasing numbers of versatile MSM resulted in little change in HIV incidence over 20 years. Anal microbicides and circumcision would decrease the HIV prevalence at 10 years from 15.6% to 12.9% and 12.7% respectively. Anal microbicides would provide similar protection to circumcision at the population level despite lower modeled efficacy (54% and 60% risk reduction, respectively). Combination of the interventions were additive: in 5 years, the reduction in HIV prevalence of the combination (-3.2%) is almost the sum of their individual reductions in HIV prevalence (-1.8% and -1.7%).

CONCLUSIONS

MSM sex role segregation and mixing, unlike changes in the sex role distribution, may be important for evaluating HIV prevention interventions in international settings. Synergies between some position-specific prevention interventions such as circumcision and anal microbicides warrant further study.

The importance of extended high viremics in models of HIV spread in South Africa

Recent studies found a substantial fraction of 'extended high viremics' among HIV-1 subtype C, the most common subtype in southern Africa. Extended high viremics are HIV infected individuals who maintain a high viral load for a longer time period than usual after the initial infection. They are more infectious during this period, and their infection progresses to full-blown AIDS and death much faster than usual. This study investigates the impact of extended high viremics on the spread of the HIV epidemic in South Africa. We develop a simple deterministic compartmental model for HIV infection that includes extended high viremics. As the available data on extended high viremics are limited, we parameterize this model using only the fraction of extended high viremics among new infections and the reduced life-span of extended high viremics. We find that without extended high viremics, the HIV prevalence in South Africa would have remained close to its 1990 level, instead of increasing to the current epidemic levels. We also find that the greater the fraction of extended high viremics among susceptibles, the greater the steady-state HIV prevalence and the more sensitive the steady-state prevalence is to the HIV transmission probability. These results suggest that extended high viremics have an impact on the HIV epidemic in South Africa; justify the need for comprehensive epidemiological studies since the current data is limited; and suggest that future models of HIV for southern Africa should explicitly model extended high viremics.

Moderno love: sexual role-based identities and HIV/STI prevention among men who have sex with men in Lima, Peru

Role-based sexual identities structure male same-sex partnerships and influence HIV/STI epidemiology among MSM in Latin America. We explored shifting relationships between sexual roles, identities and practices among MSM in Lima, Peru, and implications for HIV/STI prevention. Patterns of HIV/STI epidemiology reflected differential risks for transmission within role-based partnerships with relatively low prevalences of HIV, syphilis, and HSV-2 but higher prevalences of urethral gonorrhea/chlamydia among activo MSM compared with moderno and pasivo participants. Qualitative analysis of how MSM in Peru integrate sexual identities, roles, and practices identified four key themes: pasivo role as a gay approximation of cultural femininity; activo role as a heterosexual consolidation of masculinity; moderno role as a masculine reconceptualization of gay identity; and role-based identities as social determinants of partnership, network, and community formation. The concept of role-based sexual identities provides a framework for HIV prevention for Latin American MSM that integrates sexual identities, practices, partnerships, and networks.

Versatility and HIV vulnerability: patterns of insertive and receptive anal sex in a national sample of older Australian gay men

According to mathematical modeling, HIV is more likely to spread through a population of men who have sex with men when high numbers practice versatile anal sex roles, that is, engage in both insertive (IAI) and receptive anal intercourse (RAI). Yet, actual patterns of versatility remain largely unknown, particularly among older men who currently face growing rates of HIV. In this study, 1,135 Australian gay men aged 40 years and older completed a national online survey of their sexual health and behavior over the past 12 months. Of men who had anal intercourse, 62 % engaged in both IAI and RAI. Factors associated with being versatile included younger age (P = 0.01), higher income (P = 0.009), and larger numbers of sexual partners (P = 0.003). Among men with multiple sexual partners, 20 % were highly versatile, that is, reported similar numbers of IAI and RAI partners. Having HIV (P = 0.003) and living in a rural area (P = 0.04) were significantly associated with being highly versatile. These data point to high rates of versatility among older Australian gay men, with implications for mathematical predictions of change in HIV epidemics and for the design of future HIV prevention strategies.

Failure of serosorting to protect African American men who have sex with men from HIV infection

BACKGROUND

Serosorting is the practice of choosing sex partners or selectively using condoms based on a sex partner's perceived HIV status. The extent to which serosorting protects African American (AA) and Hispanic men who have sex with men (MSM) is unknown.

METHODS

We analyzed data collected from MSM sexually transmitted diseases clinic patients in Seattle, WA, 2001-2010. Men were asked about the HIV status of their anal sex partners in the prior year and about their condom use with partners by partner HIV status. We defined serosorters as MSM who had unprotected anal intercourse (UAI) only with partners of the same HIV status, and compared the risk of testing HIV positive among serosorters and men who reported having UAI with partners of opposite or unknown HIV status (ie, nonconcordant UAI). We used generalized estimating equations to evaluate the association of serosorting with testing HIV positive.

RESULTS

A total of 6694 MSM without a prior HIV diagnosis were tested during 13,657 visits; 274 men tested HIV positive. Serosorting was associated with a lower risk of testing HIV positive than nonconcordant UAI among white MSM (2.1 vs. 4.5%, odds ratio [OR]: 0.45, 95% confidence interval [CI]: 0.34-0.61), but not AA MSM (6.8 vs. 6.0%, OR: 1.1, 95% CI: 0.57-2.2). Among Hispanics, the risk of testing HIV positive was lower among serosorters than men engaging in nonconcordant UAI, though this was not significant (4.1 vs. 6.0%, OR: 0.67, 95% CI: 0.36-1.2).

CONCLUSIONS

In at least some AA MSM populations, serosorting does not seem to be protective against HIV infection.

A comparison of sexual behavior patterns among men who have sex with men and heterosexual men and women

OBJECTIVE

Men who have sex with men (MSM) have higher rates of HIV and other sexually transmitted infections than women and heterosexual men. This elevated risk persists across age groups and reflects biological and behavioral factors; yet, there have been few direct comparisons of sexual behavior patterns between these populations.

METHODS

We compared sexual behavior patterns of MSM and male and female heterosexuals aged 18-39 using 4 population-based random digit dialing surveys. A 1996-1998 survey in 4 US cities and 2 Seattle surveys (2003 and 2006) provided estimates for MSM; a 2003-2004 Seattle survey provided data about heterosexual men and women.

RESULTS

Sexual debut occurred earlier among MSM than heterosexuals. MSM reported longer cumulative lifetime periods of new partner acquisition than heterosexuals and a more gradual decline in new partnership formation with age. Among MSM, 86% of 18- to 24-year-olds and 72% of 35- to 39-year-olds formed a new partnership during the previous year, compared with 56% of heterosexual men and 34% of women at 18-24 years, and 21% and 10%, respectively, at 35-39 years. MSM were also more likely to choose partners >5 years older and were 2-3 times as likely as heterosexuals to report recent concurrent partnerships. MSM reported more consistent condom use during anal sex than heterosexuals reported during vaginal sex.

CONCLUSIONS

MSM have longer periods of partnership acquisition, a higher prevalence of partnership concurrency, and more age disassortative mixing than heterosexuals. These factors likely help to explain higher HIV/sexually transmitted infections rates among MSM, despite higher levels of condom use.

Mathematical models for the study of HIV spread and control amongst men who have sex with men

For a quarter of century, mathematical models have been used to study the spread and control of HIV amongst men who have sex with men (MSM). We searched MEDLINE and EMBASE databases up to the end of 2010 and reviewed this literature to summarise the methodologies used, key model developments, and the recommended strategies for HIV control amongst MSM. Of 742 studies identified, 127 studies met the inclusion criteria. Most studies employed deterministic modelling methods (80%). Over time we saw an increase in model complexity regarding antiretroviral therapy (ART), and a corresponding decrease in complexity regarding sexual behaviours. Formal estimation of model parameters was carried out in only a small proportion of the studies (22%) while model validation was considered by an even smaller proportion (17%), somewhat reducing confidence in the findings from the studies. Nonetheless, a number of common conclusions emerged, including (1) identification of the importance of assumptions regarding changes in infectivity and sexual contact rates on the impact of ART on HIV incidence, that subsequently led to empirical studies to gather these data, and (2) recommendation that multiple strategies would be required for effective HIV control amongst MSM. The role of mathematical models in studying epidemics is clear, and the lack of formal inference and validation highlights the need for further developments in this area. Improved methodologies for parameter estimation and systematic sensitivity analysis will help generate predictions that more fully express uncertainty, allowing better informed decision making in public health.

Interaction of mathematical modeling and social and behavioral HIV/AIDS research

PURPOSE OF REVIEW

HIV is transmitted within complex biobehavioral systems. Mathematical modeling can provide insight to complex population-level outcomes of various behaviors measured at an individual level.

RECENT FINDINGS

HIV models in the social and behavioral sciences can be categorized in a number of ways; here, we consider two classes of applications common in the field generally, and in the past year in particular: those models that explore significant behavioral determinants of HIV disparities within and between populations; and those models that seek to evaluate the potential impact of specific social and behavioral interventions.

SUMMARY

We discuss two overarching issues we see in the field: the need to further systematize effectiveness models of behavioral interventions, and the need for increasing investigation of the use of behavioral data in epidemic models. We believe that a recent initiative by the National Institutes of Health will qualitatively change the relationships between epidemic modeling and sociobehavioral prevention research in the coming years.

Male circumcision and risk of HIV acquisition among MSM

OBJECTIVES

To assess the association between male circumcision, insertive anal sex practices, and HIV acquisition in a cohort of MSM.

METHODS

Data were from 1824 HSV-2-seropositive, HIV-seronegative MSM, 1362 (75%) from Peru and 462 (25%) from the US, who participated in a randomized placebo-controlled trial of HSV-2 suppression for HIV prevention (HPTN 039). Circumcision status was determined by examination at enrollment. HIV testing was done every 3 months for up to 18 months. Partner-specific sexual behavior for up to the last three partners during the previous 3 months was analyzed.

RESULTS

There was no significant association between male circumcision and HIV acquisition in univariate analysis [relative risk (RR) = 0.84, 95% confidence interval (CI) 0.50-1.42]. In a prespecified multivariate analysis that assumed a linear relationship between the proportion of insertive acts and effect of circumcision on HIV acquisition, the interaction between circumcision and proportion of insertive acts was not significant (P = 0.11). In an exploratory analysis that categorized behavior with recent partners by proportion of insertive acts (<60 or ≥60% insertive acts), circumcision was associated with a nonstatistically significant 69% reduction in the risk of HIV acquisition (RR = 0.31, 95% CI 0.06-1.51) among men who reported at least 60% of insertive acts with recent male partners.

CONCLUSION

Circumcision does not have a significant protective effect against HIV acquisition among MSM from Peru and US, although there may be reduced risk for men who are primarily insertive with their male partners. This association needs to be investigated across diverse cohorts of MSM.

Sexual identity and its contribution to MSM risk behavior in Bangaluru (Bangalore), India: the results of a two-stage cluster sampling survey

In India, there are categories of MSM (hijras, kothis, double-deckers, panthis and bisexuals), which are generally associated with different HIV-risk behaviors. Our objective was to quantify differences across MSM identities (n = 357) and assess the extent they conform to typecasts that prevail in policy-orientated discourse. More feminine kothis (26%) and hijras (13%) mostly reported receptive sex, and masculine panthis (15%) and bisexuals (23%) insertive anal sex. However, behavior did not always conform to expectation, with 25% and 16% of the sample reporting both insertive and receptive anal intercourse with known and unknown noncommercial partners, respectively (p < 0.000). Although behavior often complied with stereotyped role and identity, male-with-male sexual practices were fluid. Reification of these categories in an intervention context may hinder our understanding of the differential HIV risk among MSM.

Retroviral infection in Peruvian men who have sex with men

We tested 2655 Peruvian men who have sex with men for the presence of retroviral infection. Human T cell lymphotropic virus type 1 (HTLV-1) was detected in 48 (1.8%) of the patients, HTLV-2 was detected in 28 (1.1%), and HTLV-1 and HTLV-2 were both detected in 5 (0.2%). Human immunodeficiency virus infection was detected in 329 (12.4%) of the patients; 24 (7.3%) had HTLV coinfection. Risk factors for HTLV-1 and HTLV-2 infection varied with sexual role.

Mathematical models for HIV transmission dynamics: tools for social and behavioral science research

HIV researchers have long appreciated the need to understand the social and behavioral determinants of HIV-related risk behavior, but the cumulative impact of individual behaviors on population-level HIV outcomes can be subtle and counterintuitive, and the methods for studying this are rarely part of a traditional social science or epidemiology training program. Mathematical models provide a way to examine the potential effects of the proximate biologic and behavioral determinants of HIV transmission dynamics, alone and in combination. The purpose of this article is to show how mathematical modeling studies have contributed to our understanding of the dynamics and disparities in the global spread of HIV. Our aims are to demonstrate the value that these analytic tools have for social and behavioral sciences in HIV prevention research, to identify gaps in the current literature, and to suggest directions for future research.

Degree distributions in sexual networks: a framework for evaluating evidence

OBJECTIVE

We present a likelihood based statistical framework to test the fit of power-law and alternative social process models for the degree distribution, and derive the sexually transmitted infection epidemic predictions from each model.

STUDY DESIGN

Five surveys from the United States are analyzed. Model fit is formally compared via Akaike Information Criterion and Bayesian Information Criterion, and substantively assessed via the prediction of a generalized epidemic.

RESULTS

Formal goodness-of-fit tests do not consistently identify any model as the best all around fit to the US data. Power-law models predict a generalized sexually transmitted infection epidemic in the United States, while most alternative models do not.

CONCLUSIONS

Power-law models do not fit the data better than alternative models, and they consistently make inaccurate epidemic predictions. Better models are needed to represent the behavioral basis of sexual networks and the structures that result, if these data are to be used for disease transmission modeling.

HIV-1 infection in high risk men who have sex with men in Mombasa, Kenya

BACKGROUND

The role of homosexuality and anal sex practices in the African HIV -1 epidemic is not well described. We aimed to assess the risk factors for prevalent HIV-1 infection among men who have sex with men (MSM) to guide HIV-1 prevention efforts.

METHODS

Socio-behavioural characteristics, signs and symptoms of sexually transmitted diseases (STD), and serological evidence of HIV-1 were determined for 285 MSM at enrolment into a vaccine preparedness cohort study. We used multivariate logistic regression to assess risk factors for prevalent HIV-1 infection.

RESULTS

HIV-1 prevalence was 43.0% [49/114, 95% confidence interval (CI), 34-52%] for men who reported sex with men exclusively (MSME), and 12.3% (21/171, 95% CI, 7-17%) for men who reported sex with both men and women (MSMW). Eighty-six (75%) MSME and 69 (40%) MSMW reported recent receptive anal sex. Among 174 MSM sexually active in the last week, 44% reported no use of condoms with casual partners. In the previous 3 months, 210 MSM (74%) reported payment for sex, and most clients (93%) were local residents. Prevalent HIV-1 infection was associated with recent receptive anal sex [odds ratio (OR), 6.1; 95% CI, 2.4-16], exclusive sex with men (OR, 6.3; 95% CI, 2.3-17), and increasing age (OR, 1.1 per year; 95% CI, 1.04-1.12). Only four MSM reported injecting drug use.

CONCLUSIONS

The high prevalence of HIV-1 in Kenyan MSM is probably attributable to unprotected receptive anal sex. There is an urgent need for HIV-1 prevention programmes to deliver targeted risk-reduction interventions and STD services to MSM in Kenya.

Biological and demographic causes of high HIV and sexually transmitted disease prevalence in men who have sex with men

OBJECTIVES

HIV disproportionately affects men who have sex with men (MSM). MSM and heterosexual networks are distinguished by biologically determined sexual role segregation among heterosexual individuals but not MSM, and anal/vaginal transmissibility differences. To identify how much these biological and demographic differences could explain persistent disparities in HIV/sexually transmitted disease prevalence in the United States, even were MSM and heterosexual individuals to report identical numbers of unprotected sexual partnerships per year.

METHODS

A compartmental model parameterized using two population-based surveys. Role composition was varied between MSM and heterosexual subjects (insertive-only and receptive-only versus versatile individuals) and infectivity values.

RESULTS

The absence of sexual role segregation in MSM and the differential anal/vaginal transmission probabilities led to considerable disparities in equilibrium prevalence. The US heterosexual population would only experience an epidemic comparable to MSM if the mean partner number of heterosexual individuals was increased several fold over that observed in population-based studies of either group. In order for MSM to eliminate the HIV epidemic, they would need to develop rates of unprotected sex lower than those currently exhibited by heterosexual individuals in the United States. In this model, for US heterosexual individuals to have a self-sustaining epidemic, they would need to adopt levels of unprotected sex higher than those currently exhibited by US MSM.

CONCLUSIONS

The persistence of disparities in HIV between heterosexual individuals and MSM in the United States cannot be explained solely by differences in risky sexual behavior between these two populations.

Prevalence of same-sex sexual behavior and associated characteristics among low-income urban males in Peru

BACKGROUND

Peru has a concentrated HIV epidemic in which men who have sex with men are particularly vulnerable. We describe the lifetime prevalence of same-sex sexual contact and associated risk behaviors of men in Peru's general population, regardless of their sexual identity.

METHODS AND RESULTS

A probability sample of males from low-income households in three Peruvian cities completed an epidemiologic survey addressing their sexual risk behavior, including sex with other men. Serum was tested for HSV-2, HIV, and syphilis. Urine was tested for chlamydia and gonorrhea. A total of 2,271 18-30 year old men and women were contacted, of whom 1,645 (72.4%) agreed to participate in the study. Among the sexually experienced men surveyed, 15.2% (85/558, 95% CI: 12.2%-18.2%) reported a history of sex with other men. Men ever reporting sex with men (MESM) had a lower educational level, had greater numbers of sex partners, and were more likely to engage in risk behaviors including unprotected sex with casual partners, paying for or providing compensated sex, and using illegal drugs. MESM were also more likely to have had previous STI symptoms or a prior STI diagnosis, and had a greater prevalence of HSV-2 seropositivity.

CONCLUSIONS

Many low-income Peruvian men have engaged in same-sex sexual contact and maintain greater behavioral and biological risk factors for HIV/STI transmission than non-MESM. Improved surveillance strategies for HIV and STIs among MESM are necessary to better understand the epidemiology of HIV in Latin America and to prevent its further spread.

Role versatility among men who have sex with men in urban Peru

Role versatility refers to the practice in which individual men who have sex with men (MSM) play both insertive and receptive sexual roles over time. Versatility has been thought to be relatively uncommon among Latin American MSM but possibly rising. Versatility has also been shown to be a potentially large population-level risk factor for HIV infection. In this study we examine the correlates of versatile behavior and identity among 2,655 MSM in six Peruvian cities. Versatile behavior with recent male partners was found in 9% of men and versatile ("moderno") identity was reported by 16%. Significant predictors included high education, white-collar occupation, sex work, and residence in Lima. Age was not significant in any analysis. Since sex work is negatively correlated with other predictors, versatile men appear to comprise two distinct sub-populations. Insertive-only men appear to play a strong role in bridging the HIV epidemic between MSM and women.

HIV-1, Sexually Transmitted Infections, and Sexual Behavior Trends Among Men Who Have Sex With Men in Lima, Peru

OBJECTIVE

To assess and estimate trends in HIV, sexually transmitted infections (STIs), and sexual behavior among men who have sex with men (MSM) in Lima, Peru.

DESIGN

Second-generation HIV sentinel surveillance surveys conducted in 1996, 1998, 2000, and 2002.

METHODS

Adult men reporting sex with at least 1 man during the previous year were eligible to participate. Sexual behavior and serum HIV-1 and syphilis antibodies were assessed. HIV seroincidence was estimated by a sensitive/less-sensitive enzyme immunoassay strategy. Rectal and pharyngeal swabs for Neisseria gonorrhoeae culture and a first-void urine sample for urethral leukocytes for presumptive diagnosis of urethritis were obtained. Herpes simplex virus 2 (HSV-2) antibodies were measured in 2002.

RESULTS

Although HIV prevalence increased from 18.5% to 22.3% from 1996 through 2002, bacterial prevalence declined significantly for syphilis (16.0% to 12.4%), early syphilis (8.6% to 3.4%), and rectal gonorrhea (5.1% to 0.2%). High HIV seroincidence was estimated, with the lowest (4.8%) incidence in 1998. In 2002, HSV-2 seroprevalence was 51.0%. After adjustment for age, education, and self-reported sexual identity, our data suggest that a yearly increase by 6% in the prevalence of HIV occurred among MSM in Lima, with a corresponding decline in syphilis (by 9%), early syphilis (by 18%), and rectal gonorrhea (by 64%). Condom use during last sexual intercourse increased by 26% each year with the most recent male steady partner and, among non-sex workers, by 11% with the most recent casual partner.

CONCLUSIONS

HIV continued to spread among MSM in Lima even when a decline in bacterial STIs and increase in condom use were estimated to occur. Intensification of medical and behavior prevention interventions is warranted for MSM in Peru.

Correlates of condom use in a sample of MSM in Ecuador

Background

In Ecuador, the prevalence of HIV in the general population is approximately 0.3%. However, up to 17% prevalence has been reported among specific groups of homosexual and bisexual men. The objective of this study is to explore correlates of condom use among men who have sex with men (MSM) across eight cities in Ecuador.

Methods

A cross-sectional survey design was used. A questionnaire including variables on sexual behaviour, demographics, and socio-economic characteristics was distributed to a sample of MSM in eight Ecuadorian cities.

Results

Information was obtained for 2,594 MSM across the eight cities. The largest subcategory of self-identification was active bisexuals (35%), followed by those who described themselves as "hombrados" (masculine gays, 22%). The mean age was 25 years, and the majority were unmarried (78%), with a median of 10 years of schooling (IQR 7 – 12). Regarding condom use, 55% of those interviewed had unprotected penetrative sex with each of their last three partners, and almost 25% had never used a condom. The most important correlates of condom use were single status, high life-skills rating, and high socio-economic status (RP 5.45, 95% CI 4.26 – 6.37; RP 1.84, 95% CI 1.79 – 1.86, and RP 1.20, 95% CI 1.01 – 1.31, respectively).

Conclusion

Our data illustrate the urgent need for targeted HIV-prevention programs for MSM populations in Ecuador. MSM have the highest HIV prevalence in the country, and condom use is extremely low. It is imperative that prevention strategies be re-evaluated and re-prioritized to more effectively respond to the Ecuadorian epidemic.