Concurrent sexual partnerships and HIV prevalence in five urban communities of sub-Saharan Africa

Assessing the Potential Impact of Disruptions Due to COVID-19 on HIV Among Key and Lower-Risk Populations in the Largest Cities of Cameroon and Benin

BACKGROUND

The COVID-19 pandemic indirectly impacts HIV epidemiology in Central/West Africa. We estimated the potential impact of COVID-19-related disruptions to HIV prevention/treatment services and sexual partnerships on HIV incidence and HIV-related deaths among key populations including female sex workers (FSW), their clients, men who have sex with men, and overall.

SETTING

Yaoundé (Cameroon) and Cotonou (Benin).

METHODS

We used mathematical models of HIV calibrated to city population-specific and risk population-specific demographic/behavioral/epidemic data. We estimated the relative change in 1-year HIV incidence and HIV-related deaths for various disruption scenarios of HIV prevention/treatment services and decreased casual/commercial partnerships, compared with a scenario without COVID-19.

RESULTS

A 50% reduction in condom use in all partnerships over 6 months would increase 1-year HIV incidence by 39%, 42%, 31%, and 23% among men who have sex with men, FSW, clients, and overall in Yaoundé, respectively, and 69%, 49%, and 23% among FSW, clients, and overall, respectively, in Cotonou. Combining a 6-month interruption of ART initiation and 50% reduction in HIV prevention/treatment use would increase HIV incidence by 50% and HIV-related deaths by 20%. This increase in HIV infections would be halved by a simultaneous 50% reduction in casual and commercial partnerships.

CONCLUSIONS

Reductions in condom use after COVID-19 would increase infections among key populations disproportionately, particularly FSW in Cotonou, who need uninterrupted condom provision. Disruptions in HIV prevention/treatment services have the biggest impacts on HIV infections and deaths overall, only partially mitigated by equal reductions in casual/commercial sexual partnerships. Maintaining ART provision must be prioritized to minimize short-term excess HIV-related deaths.

Concurrency measures in the era of temporal network epidemiology: a review

Diseases spread over temporal networks of interaction events between individuals. Structures of these temporal networks hold the keys to understanding epidemic propagation. One early concept of the literature to aid in discussing these structures is concurrency-quantifying individuals' tendency to form time-overlapping 'partnerships'. Although conflicting evaluations and an overabundance of operational definitions have marred the history of concurrency, it remains important, especially in the area of sexually transmitted infections. Today, much of theoretical epidemiology uses more direct models of contact patterns, and there is an emerging body of literature trying to connect methods to the concurrency literature. In this review, we will cover the development of the concept of concurrency and these new approaches.

Association between substance use and concurrent sexual relationships among urban slum dwellers in Nairobi, Kenya

While the overall incidence and prevalence of HIV/AIDS are declining in Africa, substance use-related HIV/AIDS is on the rise. The main objectives of this study were to elicit the types of commonly used substances and to examine the association between substance use and concurrent sexual relationships among slum dwellers in Kenya. Freelisting elicitation techniques were used to identify the most commonly used substances using 53 key informants. This was followed by a self-administered, structured questionnaire using a convenience sample of 506 participants. Findings from our freelisting analysis produced 27 substances that were used in the community. Analysis of the survey data shows that participants who reported using substances in the past three months were more likely to be involved in concurrent sexual relationships than those who did not (86.2% vs. 74.0%; p = .002). In the multivariable model, the odds of ever having concurrent sexual relationships were higher among participants who used any substance in the past three months (aOR 2.46; 95% CI 1.37-4.42, p < .01). The observed association between substance use and concurrent sexual relationships may be influenced by social and economic factors such as poverty and lack of opportunity among urban slum dwellers.

Differential sexual network connectivity offers a parsimonious explanation for population-level variations in the prevalence of bacterial vaginosis: a data-driven, model-supported hypothesis

BACKGROUND

The prevalence of bacterial vaginosis (BV) and vaginal microbiota types varies dramatically between different populations around the world. Understanding what underpins these differences is important, as high-diversity microbiotas associated with BV are implicated in adverse pregnancy outcomes and enhanced susceptibility to and transmission of sexually transmitted infections.

MAIN TEXT

We hypothesize that these variations in the vaginal microbiota can, in part, be explained by variations in the connectivity of sexual networks. We argue: 1) Couple-level data suggest that BV-associated bacteria can be sexually transmitted and hence high sexual network connectivity would be expected to promote the spread of BV-associated bacteria. Epidemiological studies have found positive associations between indicators of network connectivity and the prevalence of BV; 2) The relationship between BV prevalence and STI incidence/prevalence can be parsimoniously explained by differential network connectivity; 3) Studies from other mammals are generally supportive of the association between network connectivity and high-diversity vaginal microbiota.

CONCLUSION

To test this hypothesis, we propose a combination of empirical and simulation-based study designs.

It's the network, stupid: a population's sexual network connectivity determines its STI prevalence

There is little consensus as to why sexually transmitted infections (STIs), including HIV and bacterial vaginosis (BV) are more prevalent in some populations than others. Using a broad definition of sexual network connectivity that includes both structural and conductivity-related factors, we argue that the available evidence suggests that high prevalence of traditional STIs, HIV and BV can be parsimoniously explained by these populations having more connected sexual networks. Positive feedback, whereby BV and various STIs enhance the spread of other STIs, then further accentuates the spread of BV, HIV and other STIs. We review evidence that support this hypothesis and end by suggesting study designs that could further evaluate the hypothesis, as well as implications of this hypothesis for the prevention and management of STIs.

It's the network, stupid: a population's sexual network connectivity determines its STI prevalence

There is little consensus as to why sexually transmitted infections (STIs), including HIV and bacterial vaginosis (BV) are more prevalent in some populations than others. Using a broad definition of sexual network connectivity that includes both structural and conductivity-related factors, we argue that the available evidence suggests that high prevalence of traditional STIs, HIV and BV can be parsimoniously explained by these populations having more connected sexual networks. Positive feedback, whereby BV and various STIs enhance the spread of other STIs, then further accentuates the spread of BV, HIV and other STIs. We review evidence that support this hypothesis and end by suggesting study designs that could further evaluate the hypothesis, as well as implications of this hypothesis for the prevention and management of STIs.

Couple serostatus patterns in sub-Saharan Africa illuminate the relative roles of transmission rates and sexual network characteristics in HIV epidemiology

HIV prevalence has surpassed 30% in some African countries while peaking at less than 1% in others. The extent to which this variation is driven by biological factors influencing the HIV transmission rate or by variation in sexual network characteristics remains widely debated. Here, we leverage couple serostatus patterns to address this question. HIV prevalence is strongly correlated with couple serostatus patterns across the continent; in particular, high prevalence countries tend to have a lower ratio of serodiscordancy to concordant positivity. To investigate the drivers of this continental pattern, we fit an HIV transmission model to Demographic and Health Survey data from 45,041 cohabiting couples in 25 countries. In doing so, we estimated country-specific HIV transmission rates and sexual network characteristics reflective of pre-couple and extra-couple sexual contact patterns. We found that variation in the transmission rate could parsimoniously explain between-country variation in both couple serostatus patterns and prevalence. In contrast, between-country variation in pre-couple or extra-couple sexual contact rates could not explain the observed patterns. Sensitivity analyses suggest that future work should examine the robustness of this result to between-country variation in how heterogeneous infection risk is within a country, or to assortativity, i.e. the extent to which individuals at higher risk are likely to partner with each other.

High risk exposure to HIV among sexually active individuals who tested negative on rapid HIV Tests in the Tshwane District of South Africa-The importance of behavioural prevention measures

OBJECTIVE

To assess the prevalence of HIV risk behaviour among sexually active HIV sero-negative individuals in the Tshwane district of South Africa (SA).

METHODS

Demographic and HIV risk behaviour data were collected on a questionnaire from participants of a cross-sectional study that screened for early HIV infection using pooled nucleic acid amplification testing (NAAT). The study enrolled individuals who tested negative on rapid HIV tests performed at five HIV counseling and testing (HCT) clinics, which included four antenatal clinics and one general HCT clinic.

RESULTS

The study enrolled 9547 predominantly black participants (96.6%) with a median age of 27 years (interquartile range [IQR]: 23-31). There were 1661 non-pregnant and 7886 pregnant participants largely enrolled from the general and antenatal HCT clinics, respectively. NAAT detected HIV infection in 61 participants (0.6%; 95% confidence interval [CI]: 0.4-0.8) in the whole study. A high proportion of study participants, 62.8% and 63.0%, were unaware of their partner's HIV status; and also had high prevalence, 88.5% and 99.5%, of recent unprotected sex in the general and pregnant population, respectively. Consistent use of condoms was associated with protection against HIV infection in the general population. Trends of higher odds for HIV infection were observed with most demographic and HIV risk factors at univariate analysis, however, multivariate analysis did not show statistical significance for almost all these factors. A significantly lower risk of HIV infection was observed in circumcised men (p <0.001).

CONCLUSIONS

These data show that a large segment of sexually active people in the Tshwane district of SA have high risk exposure to HIV. The detection of newly diagnosed HIV infections in all study clinics reflects a wide distribution of individuals who are capable of sustaining HIV transmission in the setting where HIV risk behaviour is highly prevalent. A questionnaire that captures HIV risk behaviour would be useful during HIV counselling and testing to ensure that there is a systematic way of identifying HIV risk factors and that counselling is optimised for each individual. HIV risk behaviour surveillance could be used to inform relevant HIV prevention interventions that could be implemented at a community or population level.

Nonpaternity and Half-Siblingships as Objective Measures of Extramarital Sex: Mathematical Modeling and Simulations

Background

Understanding the epidemiology of HIV and other sexually transmitted infections (STIs) requires knowledge of sexual behavior, but self-reported behavior has limitations. We explored the reliability and validity of nonpaternity and half-siblings ratios as biomarkers of current and past extramarital sex.

Methods

An individual-based Monte Carlo simulation model was constructed to describe partnering and conception in human populations with a focus on Sub-Saharan Africa (SSA). The model was parameterized with representative biological, behavioral, and demographic data.

Results

Nonpaternity and half-siblings ratios were strongly correlated with extramarital sex, with Pearson correlation coefficients (PCC) of 0.79 (95% CI: 0.71–0.86) and 0.77 (0.68–0.84), respectively. Age-specific nonpaternity ratios correlated with past extramarital sex at time of conception for different scenarios: for example, PCC, after smoothing by moving averages, was 0.75 (0.52–0.89) in a scenario of steadily decreasing nonmarital sex and 0.39 (0.01–0.73) in a scenario of transient drops in nonmarital sex. Simulations assuming self-reported levels of extramarital sex from Kenya yielded nonpaternity levels lower than global nonpaternity data, suggesting sizable underreporting of extramarital sex.

Conclusions

Nonpaternity and half-siblings ratios are useful objective measures of extramarital sex that avoid limitations in self-reported sexual behavior.

Sub-Saharan African University Students' Beliefs about Abstinence, Condom Use, and Limiting the Number of Sexual Partners

Given the high risk of HIV infection among university students in sub-Saharan Africa, there is a need for culturally appropriate risk-reduction interventions specifically targeting this population. Efforts to reduce the risk require an understanding of the modifiable antecedents of sexual-risk behaviors. We report the results of a semi-structured elicitation survey based on the reasoned action approach to identify behavioral, normative, and control beliefs regarding abstinence, condom use, and limiting sexual partners. Two coders classified into 64 belief categories the written responses of 96 sub-Saharan African university students. Most students believed each behavior could reduce risk of HIV infection. The students reported that peer pressure and being in a risky environment made it harder to practice abstinence. Good communication made it easier to use condoms and to limit partners; however, unstable relationships made practicing these protective behaviors harder. The identified beliefs help to inform the development of theory-based HIV risk-reduction interventions.

Connecting the dots: network data and models in HIV epidemiology

Effective HIV prevention requires knowledge of the structure and dynamics of the social networks across which infections are transmitted. These networks most commonly comprise chains of sexual relationships, but in some populations, sharing of contaminated needles is also an important, or even the main mechanism that connects people in the network. Whereas network data have long been collected during survey interviews, new data sources have become increasingly common in recent years, because of advances in molecular biology and the use of partner notification services in HIV prevention and treatment programmes. We review current and emerging methods for collecting HIV-related network data, as well as modelling frameworks commonly used to infer network parameters and map potential HIV transmission pathways within the network. We discuss the relative strengths and weaknesses of existing methods and models, and we propose a research agenda for advancing network analysis in HIV epidemiology. We make the case for a combination approach that integrates multiple data sources into a coherent statistical framework.

Modeling excess zeros and heterogeneity in count data from a complex survey design with application to the demographic health survey in sub-Saharan Africa

Purpose To show a novel application of a weighted zero-inflated negative binomial model in modeling count data with excess zeros and heterogeneity to quantify the regional variation in HIV-AIDS prevalence in sub-Saharan African countries. Methods Data come from latest round of the Demographic and Health Survey (DHS) conducted in three countries (Ethiopia-2011, Kenya-2009 and Rwanda-2010) using a two-stage cluster sampling design. The outcome is an aggregate count of HIV cases in each census enumeration area of each country. The outcome data are characterized by excess zeros and heterogeneity due to clustering. We compare scale weighted zero-inflated negative binomial models with and without random effects to account for zero-inflation, complex survey design and clustering. Finally, we provide marginalized rate ratio estimates from the best zero-inflated negative binomial model. Results The best fitting zero-inflated negative binomial model is scale weighted and with a common random intercept for the three countries. Rate ratio estimates from the final model show that HIV prevalence is associated with age and gender distribution, HIV acceptance, HIV knowledge, and its regional variation is associated with divorce rate, burden of sexually transmitted diseases and rural residence. Conclusions Scale weighted zero-inflated negative binomial with proper modeling of random effects is shown to be the best model for count data from a complex survey design characterized by excess zeros and extra heterogeneity. In our data example, the final rate ratio estimates show significant regional variation in the factors associated with HIV prevalence indicating that HIV intervention strategies should be tailored to the unique factors found in each country.

The Global Epidemiology of Syphilis in the Past Century - A Systematic Review Based on Antenatal Syphilis Prevalence

BACKGROUND

How can we explain the uneven decline of syphilis around the world following the introduction of penicillin? In this paper we use antenatal syphilis prevalence (ASP) to investigate how syphilis prevalence varied worldwide in the past century, and what risk factors correlate with this variance.

METHODS

1) A systematic review using PubMed and Google Scholar was conducted to identify countries with published data relating to ASP estimates from before 1952 until the present. Eleven countries were identified (Canada, Denmark, Finland, India, Japan, Norway, Singapore, South Africa, United States of America (USA), United Kingdom (UK) and Zimbabwe). The ASP epidemic curve for each population was depicted graphically. In South Africa and the USA, results are reported separately for the black and white populations. 2) National antenatal syphilis prevalence estimates for 1990 to 1999 and 2008 were taken from an Institute for Health Metrics and Evaluation database on the prevalence of syphilis in low risk populations compiled for the Global Burden of Diseases study and from a recent review paper respectively. National ASPs were depicted graphically and regional median ASPs were calculated for both time periods. 3) Linear regression was used to test for an association between ASP in 1990-1999 and 2008 and four risk factors (efficacy of syphilis screening/treatment, health expenditure, GDP per capita and circumcision prevalence). WHO world regions were included as potential explanatory variables.

RESULTS

In most populations, ASP dropped to under 1% before 1960. In Zimbabwe and black South Africans, ASP was high in the pre-penicillin period, dropped in the post-penicillin period, but then plateaued at around 6% until the end of the 20th century when ASP dropped to just above 1%. In black Americans, ASP declined in the post penicillin period, but plateaued at 3-5% thereafter. ASP was statistically significantly higher in sub-Saharan Africa in 1990-1999 and 2008 than in the other world regions (P < 0.001). On multivariate analysis in both time periods, ASP was only associated with residence in sub-Saharan Africa.

CONCLUSIONS

Further research is necessary to elucidate the reasons for the higher prevalence of syphilis in sub-Saharan Africa.

Leveraging changing gender norms to address concurrency: focus group findings from South African university students

Background This study aims to complement recent research on sexual concurrency in South Africa by providing a deeper understanding of women's roles and motivations for engaging in and accepting their partners' concurrency. Our goal is to inform the implementation of more effective interventions that embrace the powerful role that women can play in healthy sexual decision-making in consensual relationships.

METHODS

We conducted 12 focus groups with male and female students at the University of KwaZulu-Natal. Drawing on a subset of those focus groups, we examined the gender norms underpinning the apparently widespread acceptance of concurrent sexual partnerships. Our analysis focusses on women's attitudes and behaviours towards concurrency - from both men's and women's perspectives - with a goal of identifying opportunities to engage women as agents of change in sexual partnership patterns in their communities.

RESULTS

Our findings indicate that: (1) concurrent sexual partnerships were the norm among male students and increasingly common among female students; (2) material gain and changes in women's perceptions of their roles and power in relationships were the primary female motives for concurrency; (3) peer pressure, a perceived innate need and a fear of being alone were the primary male motives for concurrency; (4) women often know that their partners are cheating and stay with them because they believe they are the most important partner, for financial reasons, or because they worry they will not find another partner.

CONCLUSIONS

HIV prevention interventions in populations where concurrency is common would benefit from emphasising women's role and power in taking greater control of their own sexual decision-making in consensual and nonviolent relationships.

Partner concurrency and HIV infection risk in South Africa

BACKGROUND

The relationship between concurrent sexual partnerships and HIV risk is not fully understood. Evidence on the relationship between partner concurrency (one's sexual partner has another partner) and individual HIV risk is limited. In this study, the relationship between reported sexual partner concurrency and the risk of HIV infection was explored among South Africans.

METHODS

Data from the third South African national HIV survey were used. In this survey, performed in 2008, questionnaires and HIV tests were administered to a nationally representative sample of 15031 persons. Bivariate analysis and multiple logistic regression were used to evaluate the relationship between partner concurrency and HIV serostatus. Spearman's correlation was used to test the association between the prevalence of HIV and partner concurrency by race in women.

RESULTS

The relationship between HIV prevalence and partner concurrency varied by race. At a cross-racial level there was a positive association between HIV prevalence and partner concurrency for women (rho=0.95, p=0.05). Among coloured, white, and Indian persons, HIV prevalence and partner concurrency rates were too low to allow further statistical testing. In the bivariate analysis, black African women who reported partner concurrency had a higher prevalence of HIV (36% (95% confidence interval (CI) 29.7-42.0) vs. 23% (95% CI 19.6-26.1), p<0.001). After controlling for demographic, social, biological, and behavioural variables, the association remained statistically significant (adjusted odds ratio (aOR) 1.4, p=0.04). The association was stronger among 15-29-year-old black African women (aOR 1.8, p=0.03) than among women aged 30 years and older (aOR 1.3, p=0.36).

CONCLUSIONS

These results suggest that partner concurrency may increase the HIV infection risk for black South African women, and in particular, for younger women.

A network-level explanation for the differences in HIV prevalence in South Africa's racial groups

Analyses of individual-level risk factors have not been able to adequately explain why HIV has spread so extensively in southern Africa and why this has occurred especially within certain racial or ethnic groups. Using data from a longitudinal study of a representative sample of adolescents aged 14-22 living in Cape Town, South Africa, this article presents evidence of how differences in individual-level risk factors as well as sexual network structures between different racial or ethnic groups may help explain the differential spread of HIV in South Africa. Particular emphasis is placed on how levels of partner concurrency, respondent concurrency, mutual concurrency, serial concurrency and numbers of sexual partners and an average early age of sexual debut combine in different ways in the different racial or ethnic groups to create networks of sexual partnerships that differ in the density of their interconnections and hence potential for HIV spread. These network-level differences offer a potential explanation for the observed generalised HIV epidemic seen among the population of black South Africans.

Risky sexual behaviors among female youth in Tiss Abay, a semi-urban area of the Amhara Region, Ethiopia

BACKGROUND

Little is known about sexual risks and associated factors about female youths in semi-urban areas of Ethiopia. This study aimed to describe the nature and magnitude of risky sexual behaviors, and the socio-demographic and behavioral determinants among female youths in Tiss Abay, a semi-urban area on the outskirts of Bahir Dar City of the Amhara Region in northern Ethiopia.

METHODS

A cross-sectional census type study was conducted among female youths who were unmarried and aged 15-29 years in September 2011.

RESULTS

711 female youths participated in the study, with the mean age of initiation of sex of 78.6% being16.73±2.53 years. Only 52(9.3%) used condom during the first sex. Within the last 12 months, 509(71.6%) had sexual intercourse and 278(54.6%) had two or more sex partners, and 316(62.1%) did not use condom during their last sex. Sex under the influence of substances was reported by 350(68.8%), and a third of the recent sexes were against the will of participants. One or more risky sexual practices were reported by 503(70.3%) participants, including: multiple sexual partnerships, inconsistently using or not using condoms, sex under the influence of alcohol and/or sex immediately after watching pornography. Age group, current marital status, drinking homemade alcohol, chewing 'khat', watching pornography and using any form of stimulant substances were the predictors of risky sexual behavior. Watching pornography before sex and sex for transaction were the predicators of not using condom during most recent sex.

CONCLUSIONS

Risky sexual behaviors were very common among the female youths in Tiss Abay. Initiation of context-based interventions, such as raising awareness about the risks, safer sex practices, condom promotion and integration of gender issues in the programs are recommended.

A new approach to measuring partnership concurrency and its association with HIV risk in couples

Empirical estimates of the association between concurrent partnerships (CP) and HIV risk are affected by non-sampling errors in survey data on CPs, e.g., because respondents misreport the extent of their CPs. We propose a new approach to measuring CPs in couples, which permits assessing how respondent errors affect estimates of the association between CPs and HIV risk. Each couple member is asked (1) to report whether s/he has engaged in CPs and (2) to assess whether his/her partner has engaged in CPs, since their couple started. Cross-tabulating these data yields multiple classifications (with varying combinations of sensitivity/specificity) of the CPs of each couple member. We then measure the association between CPs and HIV outcomes according to each classification. The resulting range of estimates is an indicator of the uncertainty associated with respondent errors. We tested this approach using data on 520 matched couples drawn from the Likoma Network Study. Results suggest that existing tests of the concurrency hypothesis are affected by significant uncertainty.

Concurrent partnerships and HIV risk among men who have sex with men in New York City

BACKGROUND

Concurrent partnerships are a significant public health concern among men who have sex with men (MSM). This study describes the prevalence of concurrency and its association with serodiscordant/serostatus unknown unprotected anal or vaginal intercourse (SDUI) among MSM in New York City.

METHODS

A total of 1458 MSM completed a social and sexual network inventory about their male and female sex partners, including concurrency, in the last 3 months. Logistic regression identified factors associated with SDUI.

RESULTS

Median age was 29 years. The proportion of participants who reported being HIV+ was 23.5%. The men reported a mean of 3.2 male partners in the last 3 months. The proportion of MSM who reported having recent SDUI was 16.6%. More than half (63.2%) described having concurrent sex partners (individual concurrency based on overlapping dates of relationships); 71.5% reported having partners whom they believed had concurrent partners (perceived partner concurrency); and 56.1% reported that both they and their partners had concurrent partners (reciprocal concurrency). Among HIV+ men by self-report, having SDUI was positively associated with individual concurrency, any alcohol use during sex, having more male sex partners, and not having a main partner. Among self-reported HIV- men, having SDUI was positively associated with perceived partner concurrency, lower education level, any alcohol and drug use during sex, having more male sex partners, and having an anonymous partner.

CONCLUSIONS

Concurrency was common among MSM. The association of SDUI with individual and perceived partner concurrency, along with substance use during sex, having an anonymous partner, and having many sex partners likely further increases HIV acquisition and transmission risk among MSM. HIV prevention interventions should address concurrency among MSM.

Uthando Lwethu ('our love'): a protocol for a couples-based intervention to increase testing for HIV: a randomized controlled trial in rural KwaZulu-Natal, South Africa

Background

Couples-based HIV counseling and testing (CHCT) is a proven strategy to reduce the risk of HIV transmission between partners, but uptake of CHCT is low. We describe the study design of a randomized controlled trial (RCT) aimed to increase participation in CHCT and reduce sexual risk behavior for HIV among heterosexual couples in rural KwaZulu-Natal, South Africa. We hypothesize that the rate of participation in CHCT will be higher and sexual risk behavior will be lower in the intervention group as compared to the control.

Methods/design

Heterosexual couples (N = 350 couples, 700 individuals) are being recruited to participate in a randomized trial of a couples-based intervention comprising two group sessions (one mixed gender, one single gender) and four couples’ counseling sessions. Couples must have been in a relationship together for at least 6 months. Quantitative assessments are conducted via mobile phones by gender-matched interviewers at baseline, 3, 6, and 9 months post-randomization. Intervention content is aimed to improve relationship dynamics, and includes communication skills and setting goals regarding CHCT.

Discussion

The Uthando Lwethu (‘our love’) intervention is the first couples-based intervention to have CHCT as its outcome. We are also targeting reductions in unprotected sex. CHCT necessitates the testing and mutual disclosure of both partners, conditions that are essential for improving subsequent outcomes such as disclosure of HIV status, sexual risk reduction, and improving treatment outcomes. Thus, improving rates of CHCT has the potential to improve health outcomes for heterosexual couples in a rural area of South Africa that is highly impacted by HIV. The results of our ongoing clinical trial will provide much needed information regarding whether a relationship-focused approach is effective in increasing rates of participation in CHCT. Our intervention represents an attempt to move away from individual-level conceptualizations, to a more integrated approach for HIV prevention.

Trial registration

Study Name: Couples in Context: An RCT of a Couples-based HIV Prevention Intervention

ClinicalTrials.gov identifier: NCT01953133.

South African clinical trial registration number: DOH-27-0212-3937

Multiple partners and condom use among students at a South African University

The prevalence of HIV in sub-Saharan Africa is the highest in the world. Young people, including university students, are at risk. Many sexually active young people have multiple partners, but little is known about how university students who have multiple partners differ from those who do not. This study examined such differences among randomly selected first-year students at a university in the Eastern Cape Province, South Africa, who completed a confidential questionnaire via audio computer-assisted self-interviewing. Of 201 participants, 93 (46.3%) reported sexual intercourse in the previous 3 months. Of those, 52 (55.91%) reported sexual intercourse with more than one partner in the past 3 months. Controlling for gender, students who reported multiple partners were younger at first coitus, had a greater number of lifetime coital partners, and reported more frequent coitus and unprotected coitus but a lower proportion of condom-protected coital acts in the past 3 months than did those reporting only one partner. However, those reporting multiple partners and one partner did not differ in religiosity, drinking problems, or victimization by childhood sexual abuse. HIV/sexually transmitted disease risk reduction interventions must address unprotected coitus and failure to use condoms among university students reporting multiple partners.

Measuring prevalence and correlates of concurrent sexual partnerships among young sexually active men in Kisumu, Kenya

Our objectives were to: (1) compare multiple measures of partnership concurrency, including the UNAIDS-recommended definition and (2) describe the prevalence and correlates of concurrent sexual partnerships among young Kenyan men. We analyzed 10,907 lifetime partnerships of 1,368 men ages 18-24 years enrolled in a randomized trial of male circumcision to reduce HIV-1 incidence in Kisumu. Partnership concurrency was determined by overlapping dates and examined over varying recall periods and assumptions. The lifetime prevalence of concurrency was 77 %. Sixty-one percent of all partnerships were concurrent and factors associated with concurrency differed by partner type. Point prevalence of concurrency at the time of the interview was consistently the highest and UNAIDS-recommended definition was the most conservative (25 vs. 18 % at baseline, respectively). Estimates of concurrency were influenced by methods for definition and measurement. Regardless of definition, concurrent partnerships are frequent in this population of young, sexually active men in high HIV prevalence Kisumu, Kenya.

Classification of incidence and prevalence of certain sexually transmitted infections by world regions

OBJECTIVES

This study sought to assess if there is a meaningful way in which variations in sexually transmitted infection (STI) prevalence can be classified at the level of world regions.

METHODS

Linear regression was performed to assess if the incidence and prevalence of six STIs (HIV, herpes simplex virus type 2, chlamydia, gonorrhea, syphilis, and trichomoniasis) by world region was positively correlated. Partitioning around medoids (PAM) was then used to assess if the regions of the world can be classified according to the incidence and prevalence of these STIs.

RESULTS

We found evidence that STI incidence/prevalence varies considerably in different regions around the world. Linear regression revealed that the incidence and prevalence of certain STIs by world region was positively correlated (Pearson's correlation coefficient varied from 0.664 to 0.985). PAM provided support for dividing the world regions into two, three, or four STI incidence/prevalence categories, but it provided most support for the two-category system. In each of these systems the East Asia/Pacific and North Africa/Middle East regions were in the lowest STI category and Sub-Saharan Africa was the only region in the high STI category.

CONCLUSIONS

The incidence and prevalence of certain STIs by world region are positively correlated. The world regions can be meaningfully classified according to STI incidence/prevalence.

The implications of respondent concurrency on sex partner risk in a national, web-based study of men who have sex with men in the United States

BACKGROUND

Men who have sex with men (MSM) represent the largest HIV risk group in the United States. Sexual concurrency catalyzes HIV transmission in populations by increasing the indirect exposure of one's sex partners to one another. Although individual-level (egocentric) designs have demonstrated a high prevalence of concurrency among MSM respondents, methods are lacking for understanding the exposure implications for partners (dyads) reported in such studies.

METHODS

A new technique for manipulating egocentrically collected partnership timing data to measure the degree to which respondents' patterns of concurrency and serial monogamy resulted in the indirect exposure of respondents' partners to other partners was developed. Two outcomes were constructed for each partner: any concurrent or serially monogamous exposure to another partner (any exposure) and any concurrent exposure to another partner, irrespective of serial monogamy (any concurrent exposure). Reports of unprotected anal intercourse (UAI) were incorporated to construct the outcomes of 'any UAI exposure' and 'any concurrent UAI exposure.' This method was applied to an online study of MSM aged ≥18 years, with comparisons made by partner's race-ethnicity, age, type, and meeting location.

RESULTS

Among 4060 repeat partners of 2449 MSM, 73% had any exposure in the previous 6 months; 58% had any concurrent exposure. Among UAI partners, 37% had concurrent UAI exposure. Black UAI partners were more likely than whites to have any concurrent UAI exposure [unadjusted odds ratio (95% confidence interval) = 1.34 (1.05 to 1.70)], as were casual UAI partners relative to main partners [unadjusted odds ratio (95% confidence interval) = 4.37 (3.58 to 5.35)]. In adjusted models, black UAI partners were significantly more likely to have any UAI exposure, but not concurrent UAI exposure. Casual UAI partners remained more exposed by both outcomes.

CONCLUSIONS

Sex partners of MSM, particularly casual and black non-Hispanic partners, face a high degree of exposure to other partners.

Coital frequency and condom use in monogamous and concurrent sexual relationships in Cape Town, South Africa

Introduction

A decreased frequency of unprotected sex during episodes of concurrent relationships may dramatically reduce the role of concurrency in accelerating the spread of HIV. Such a decrease could be the result of coital dilution – the reduction in per-partner coital frequency from additional partners – and/or increased condom use during concurrency. To study the effect of concurrency on the frequency of unprotected sex, we examined sexual behaviour data from three communities with high HIV prevalence around Cape Town, South Africa.

Methods

We conducted a cross-sectional survey from June 2011 to February 2012 using audio computer-assisted self-interviewing to reconstruct one-year sexual histories, with a focus on coital frequency and condom use. Participants were randomly sampled from a previous TB and HIV prevalence survey. Mixed effects logistic and Poisson regression models were fitted to data from 527 sexually active adults reporting on 1210 relationship episodes to evaluate the effect of concurrency status on consistent condom use and coital frequency.

Results

The median of the per-partner weekly average coital frequency was 2 (IQR: 1–3), and consistent condom use was reported for 36% of the relationship episodes. Neither per-partner coital frequency nor consistent condom use changed significantly during episodes of concurrency (aIRR=1.05; 95% confidence interval (CI): 0.99–1.24 and aOR=1.01; 95% CI: 0.38–2.68, respectively). Being male, coloured, having a tertiary education, and having a relationship between 2 weeks and 9 months were associated with higher coital frequencies. Being coloured, and having a relationship lasting for more than 9 months, was associated with inconsistent condom use.

Conclusions

We found no evidence for coital dilution or for increased condom use during concurrent relationship episodes in three communities around Cape Town with high HIV prevalence. Given the low levels of self-reported consistent condom use, our findings suggest that if the frequency of unprotected sex with each of the sexual partners is sustained during concurrent relationships, HIV-positive individuals with concurrent partners may disproportionately contribute to onward HIV transmission.

Polygyny and women's health in rural Mali

Women's social networks and social power are increasingly seen as important factors modulating their health in sub-Saharan Africa. Polygyny, a common marital structure in many societies, mediates important intra-household relationships by requiring both competition and co-operation among co-wives. Using mixed methods, semi-structured questionnaires were administered to 298 women aged 15-84 living in the Kolondiéba region of rural Mali in 1999, and supplemented by detailed interviews with 40 women. Three categories of outcome were explored: illness experience, therapeutic itinerary and social support received. Quantitative data were analysed using regression analysis and qualitative data using a grounded theory approach. In quantitative analyses, controlling for age and household wealth index, senior wives were less likely to be escorted to a healer by their husbands during illness than were junior wives or monogamous women. Polygynous women were also less likely to obtain a treatment for which there was a monetary fee. Fewer than one-third of polygynous women reported the assistance of a co-wife during illness in any given task. In qualitative analyses, women further related varied mechanisms through which polygyny impacted their health trajectories. These ranged from strongly supportive relationships, to jealousy because of unequal health or fertility, bias in emotional and material support provided by husbands, and accusations of wrong-doing and witchcraft. This study highlights the need for more prospective mixed methods analyses to further clarify the impact of polygyny on women's health-related experiences and behaviours in sub-Saharan Africa.

HIV infection and sexual partnerships and behaviour among adolescent girls in Nairobi, Kenya

Early sexual partnerships place young women in sub-Saharan Africa at high risk for HIV. Few studies have examined both individual- and partnership-level characteristics of sexual relationships among adolescent girls. A cross-sectional survey of sexual history and partnerships was conducted among 761 adolescent girls aged 15-19 years in Nairobi, Kenya. Rapid HIV testing was conducted and correlates of HIV infection were determined using multivariate logistic regression. The HIV prevalence was 7% and seropositive adolescents had a younger age at sexual debut (P < 0.01), more sexual partners in 12 months (P = 0.03), and were more likely to report transactional or non-consensual sex (P < 0.01). Girls who reported not knowing their partner's HIV status were 14 times as likely to be HIV-seropositive than girls who knew their partner's status (adjusted odds ratio: 14.2 [1.8, 109.3]). Public health messages to promote HIV testing and disclosure within partnerships could reduce sexual risk behaviours and HIV transmission among adolescents.

Measuring and modelling concurrency

This article explores three critical topics discussed in the recent debate over concurrency (overlapping sexual partnerships): measurement of the prevalence of concurrency, mathematical modelling of concurrency and HIV epidemic dynamics, and measuring the correlation between HIV and concurrency. The focus of the article is the concurrency hypothesis - the proposition that presumed high prevalence of concurrency explains sub-Saharan Africa's exceptionally high HIV prevalence. Recent surveys using improved questionnaire design show reported concurrency ranging from 0.8% to 7.6% in the region. Even after adjusting for plausible levels of reporting errors, appropriately parameterized sexual network models of HIV epidemics do not generate sustainable epidemic trajectories (avoid epidemic extinction) at levels of concurrency found in recent surveys in sub-Saharan Africa. Efforts to support the concurrency hypothesis with a statistical correlation between HIV incidence and concurrency prevalence are not yet successful. Two decades of efforts to find evidence in support of the concurrency hypothesis have failed to build a convincing case.

Changes in HIV-related behaviours, knowledge and testing among refugees and surrounding national populations: a multicountry study

To our knowledge, there is currently no published data on the prevalence of risky sex over time as displaced populations settle into long-term post-emergency refugee camps. To measure trends in HIV-related behaviours, we conducted a series of cross-sectional HIV behavioural surveillance surveys among refugees and surrounding community residents living in Kenya, Tanzania and Uganda, at baseline in 2004/2005 and at follow-up in 2010/2011. We selected participants using two-stage cluster sampling, except in the Tanzanian refugee camp where systematic random sampling was employed. Participants had to reside in a selected household for more than weeks and aged between 15 and 49 years. We interviewed 11,582 participants (6448 at baseline and 5134 at follow-up) in three camps and their surrounding communities. The prevalence of multiple sexual partnerships ranged between 10.1 and 32.6% at baseline and 4.2 and 20.1% at follow-up, casual partnerships ranged between 8.0 and 33.2% at baseline and 3.5 and 17.4% at follow-up, and transactional partnerships between 1.1 and 14.0% at baseline and 0.8 and 12.0% at follow-up. The prevalence of multiple partnerships and casual sex in the Kenyan and Ugandan camps was not higher than among nationals. To our knowledge these data are the first to describe and compare trends in the prevalence of risky sex among conflict-affected populations and nationals living nearby. The large reductions in risky sexual partnerships are promising and possibly indicative of the success of HIV prevention programs. However, evaluation of specific prevention programmes remains necessary to assess which, and to what extent, specific activities contributed to behavioural change. Notably, refugees had lower levels of multiple and casual sexual partnerships than nationals in Kenya and Uganda and thus should not automatically be assumed to have higher levels of risky sexual behaviours than neighbouring nationals elsewhere.

Casual sex and concurrent sexual partnerships among young people from an Yi community with a high prevalence of HIV in China

Liangshan Prefecture in Sichuan province, China, has a high prevalence of HIV infection, which is reflective of a change in the mode of transmission from injection drug use (IDU) to heterosexual intercourse. However, few studies focus on HIV-related heterosexual risk behaviours among the majority Yi population. The objectives of this study were to explore the characteristics of an egocentric sexual network and estimate the prevalence of casual sexual behaviour. Yi villagers (n=108), aged 15-35 years, who reported having had sex within the previous year were interviewed as to their sexual behaviours and networks. In-depth interviews and focus group discussions provided supplementary information on sexual norms. Logistic regression analysis was used to calculate unadjusted odds ratios (ORs) and 95% confidence intervals (CIs). Most of the respondents reported having had casual sex at some time in their life, and 66.7% reported multiple sexual partnerships. Only 21.3% reported ever having used a condom. During the study year, a total of 137 partners were involved in 153 sexual partnerships. Among the reported sexual partnerships, 67.3% originated from a casual sexual relationship. For network members in components of size ≥ 3, 56.9% were involved in concurrent sexual partnerships. Having never been married (OR: 2.11; 95% CI: 1.03-4.33) and younger age (OR: 0.89; 95% CI: 0.83-0.95) were both associated with being in a component of size ≥ 3. Size (OR: 2.99; 95% CI: 1.17-7.66), pair (OR: 0.54; 95% CI: 0.39-0.74), the number of weak components of the egocentric sexual network (OR: 30.04; 95% CI: 6.47-139.46) and gender (OR: 0.19; 95% CI: 0.06-0.67) were all associated with being in concurrent sexual partnerships. HIV-related interventions for the Yi ethnic minority in Sichuan province must therefore address concurrent sexual partnerships and promote condom use.

Molecular epidemiology of HIV-1 transmission in a cohort of HIV-1 concordant heterosexual couples from Dakar, Senegal

Background

A large number of HIV-1 infections in Africa occur in married couples. The predominant direction of intracouple transmission and the principal external origins of infection remain important issues of debate.

Methods

We investigated HIV-1 transmission in 46 HIV-1 concordant positive couples from Dakar, Senegal. Intracouple transmission was confirmed by maximum-likelihood phylogenetic analysis and pairwise distance comparisons of HIV-1 env gp41 sequences from both partners. Standardized interview data were used to deduce the direction as well as the external sources of the intracouple transmissions.

Results

Conservative molecular analyses showed linked viruses in 34 (74%) couples, unlinked viruses in 6 (13%) couples, and indeterminate results for 6 (13%) couples. The interview data corresponded completely with the molecular analyses: all linked couples reported internal transmission and all unlinked couples reported external sources of infection. The majority of linked couples (93%) reported the husband as internal source of infection. These husbands most frequently (82%) reported an occasional sexual relationship as external source of infection. Pairwise comparisons of the CD4 count, antiretroviral therapy status, and the proportion of gp41 ambiguous base pairs within transmission pairs correlated with the reported order of infection events.

Conclusions

In this suburban Senegalese population, a majority of HIV-1 concordant couples showed linked HIV-1 transmission with the husband as likely index partner. Our data emphasize the risk of married women for acquiring HIV-1 as a result of the occasional sexual relationships of their husbands.

Concurrent sexual partnerships among urban African American high-risk women with main sex partners

To determine correlates of concurrent sexual partnerships among high-risk low-income urban African American women, survey responses of 337 women who had main sexual partners for over 6 months and reported high-risk behaviors were analyzed; 142 of these women also reported other sexual partnerships within the past 90 days. Unadjusted analyses showed that concurrency was significantly associated with relationship status, sexual debut, forced sex, incarceration of self and partners, depression, drug use, known or suspected partner nonmonogamy, and partner drug use. Age of sexual debut, relationship status, and indicators of problem drug use remained significantly associated with concurrency when controlling for individual factors, and only indicators of problem drug use and known or suspected partner nonmonogamy remained significantly associated with concurrency when also controlling for partner characteristics. Our results suggest the presence of extensive sexual networks within this population and document the need for interventions that address drug abuse and partnership instability. Moreover, the strong association between concurrency and perceptions of partners' nonmonogamy suggest the need for intervention to target men and women in this core group.

Concurrent sexual partnerships and sexually transmitted diseases in Russia

BACKGROUND

Sexual concurrency is associated with higher prevalence of sexually transmitted diseases (STDs) including HIV. However, most studies have focused only on the concurrency of the individual participant (individual concurrency) and not on concurrency of their sexual partners (partner concurrency). Furthermore, limited concurrency information is available in Russia where HIV epidemic is growing rapidly. We therefore examine the prevalence and correlates of individual and partner concurrency, and determine whether either type of concurrency is associated with diagnosed STDs among STD clinic attendees in St. Petersburg, Russia.

METHODS

In total, 799 attendees were recruited into a cross-sectional study between 2006 and 2008. A questionnaire collected information on demographics, medical history, sexual behaviors, and up to 3 sexual partners during the preceding year.

RESULTS

The prevalence of individual and partner concurrency was 24.7% and 45.4%, respectively. Both were correlated with marital status, weekly alcohol consumption, age at first sex, and number of lifetime sexual partners. Partner concurrency was significantly associated with diagnosed STDs (odds ratio = 2.06; 95% confidence interval = 1.35-3.15). No significant association between individual concurrency and STDs was observed.

CONCLUSIONS

Partner concurrency, not individual concurrency, is independently associated with increased odds of having an STD in the studied population.

Sexual partnership patterns in malawi: implications for HIV/STI transmission

BACKGROUND

Concurrent sexual partnerships are believed to play an important role in HIV transmission in sub-Saharan Africa, but the contributions of concurrency to HIV and sexually transmitted infection (STI) spread depend on the details of infectious periods and relationship patterns. To contribute to the understanding of sexual partnership patterns in this region, we estimated partnership lengths, temporal gaps between partners, and periods of overlap across partners at an STI clinic in Lilongwe, Malawi.

METHODS

Participants underwent physical examinations and HIV tests, and responded to questionnaires about demographics and risk behaviors, including detailed questions about a maximum of 3 sexual partners in the previous 2 months. We calculated partnership length as the time between the first and most recent sexual contact with a partner, and gap length as the time between the most recent contact with 1 partner and the first contact with the next. We defined concurrent and consecutive partnerships as gap length ≤0 days and gap length >0 days, respectively.

RESULTS

In the study population (n = 183), 86% reported 0 or 1 partner, 5% reported multiple consecutive partnerships, and 9% reported concurrency. The mean partnership length was 858 days (median = 176 days). Gaps between consecutive partnerships were short (mean = 21 days), and overlaps across concurrent partners tended to be long (mean = 246 days).

CONCLUSIONS

Multiple sexual partnerships were uncommon, and partnerships were long on average. Among those reporting multiple recent partners, both long-term concurrency and narrowly spaced consecutive partnerships could present substantial risk for efficient transmission of HIV and classical STIs.

Extraspousal partnerships in a community in rural Uganda with high HIV prevalence: a cross-sectional population-based study using linked spousal data

BACKGROUND

The role of concurrent sexual partnerships in the HIV epidemic in sub-Saharan Africa is not well understood. Although most infections in Africa occur among married individuals, transmission may occur from both spousal and extraspousal partnerships. This article explores extraspousal partnerships as a form of concurrency, examining the association with HIV status, demographic characteristics, and sexual behaviors in a population-based cohort in rural Uganda.

METHODS

Prevalence of extraspousal partnerships was estimated using cross-sectional data from 2008, and adjusted odds ratios (aOR) were estimated for factors associated with the prevalence of extraspousal partnerships using logistic regression. Among men who were not in polygynous marriages, we used linked spousal data to investigate the association between extraspousal partnerships and wives' serostatus.

RESULTS

Extraspousal partnerships in the past year were reported by 17% of married men and 2% of married women. Among both men and women, extraspousal partnerships were associated with not knowing their partners' HIV status (men: aOR = 1.74; 95% CI: 1.13 to 2.67; women: aOR = 1.76; 95% CI: 1.13 to 2.75), and extraspousal partnerships were also associated with increased condom use for men. There was no evidence that men reporting extraspousal partnerships were at increased risk of HIV (aOR = 0.98; 95% CI: 0.48 to 2.01), or that a woman's risk of HIV was associated with her husband reporting extraspousal partnerships (aOR = 0.68; 95% CI: 0.29 to 1.57).

CONCLUSIONS

For both men and women, extraspousal partnerships were associated with not knowing their partners' HIV status. There was no evidence of an association of extraspousal partnerships with HIV serostatus in this cross-sectional analysis.

Sexual behaviour and HIV sero-discordance among HIV patients receiving HAART in rural Uganda

Globally, HIV sero-discordance is a major public health problem, due to increased risk of HIV transmission to HIV-negative partners. From January to August 2009, we assessed the sexual behaviour of HIV-infected patients attending an HIV treatment centre in Uganda and analysed characteristics associated with HIV sero-discordance. Of the 278 respondents, 256 (92.1%) were female, 218 (78.1%) were on antiretroviral drugs and 107 (38.7%) belonged to a sero-discordant couple. In the prior 3 months, 238 (88.5%) had more than one sexual partner and 98 (35.8%) had acquired new sexual partners. Only 171 (61.5%) had ever disclosed sero-status to main sexual partners. Participants who had changed sexual partners in the previous 3 months were more likely to be sero-discordant (OR 1.87, 95% CI 1.13, 3.11). Respondents who used condoms during their last sexual intercourse and those currently on ARVs were significantly less likely to be sero-discordant (OR 0.52 95% CI 0.28, 0.96 and OR 0.52 95% CI 0.30, 0.94, respectively). Only disclosure of sero-status was independently though inversely associated with discordance (adjusted OR 0.41, 95% CI 0.20, 0.64). Our findings indicate that HIV patients continue exhibiting high risk behaviour characterised by changing sexual partners, having multiple sexual partners and non-use of condoms.

Assessing effectiveness and cost-effectiveness of concurrency reduction for HIV prevention

We estimated the effectiveness and cost-effectiveness of changes in concurrent sexual partnerships in reducing the spread of HIV in sub-Saharan Africa. Using data from Swaziland, Tanzania, Uganda and Zambia, we estimated country-specific concurrency behaviour from sexual behaviour survey data on the number of partners in the past 12 months, and we developed a network model to compare the impact of three behaviour changes on the HIV epidemic: (1) changes in concurrent partnership patterns to strict monogamy; (2) partnership reduction among those with the greatest number of partners; and (3) partnership reduction among all individuals. We estimated the number of new HIV infections over 10 years and the cost per infection averted. Given our assumptions and model structure, we find that reducing concurrency among high-risk individuals averts the most infections and increasing monogamy the least (11.7% versus 8.7% reduction in new infections, on average, for a 10% reduction in concurrent partnerships). A campaign that costs US$1 per person annually is likely cost-saving if it reduces concurrency by 9% on average, given our baseline estimates of concurrency. In sensitivity analysis, the rank ordering of behaviour change scenarios was unaffected by potential over-estimation of concurrency, though the number of infections averted decreased and the cost per HIV infection averted increased. Concurrency reduction programmes may be effective and cost-effective in reducing HIV incidence in sub-Saharan Africa if they can achieve even modest impacts at similar costs to past mass media campaigns in the region. Reduced concurrency among high-risk individuals appears to be most effective in reducing HIV incidence, but concurrency reduction in other risk groups may yield nearly as much benefit.

Gendered HIV risk patterns among polygynous sero-discordant couples in Uganda

Stable serodiscordant relationships and sexual concurrency are pathways that contribute to the HIV epidemic in sub-Saharan Africa. However whether polygyny imparts the same risks as informal concurrent relationships remains an open research question. Using data collected at enrollment from a cohort study of sero-discordant couples, this analysis investigates how polygynous relationships differ from those involving only a single female spouse and whether men involved in polygynous partnerships are more likely to report HIV-risk behaviour than those in single spouse partnerships. Of 444 enrolled couples, 111 (25%) were polygynous and 333 (75%) were single-spouse partnerships. We found that polygynous men were more likely to report controlling sexual decision-making and to report any unprotected sex with unknown sero-status partner. After controlling for potential confounders, polygynous men were still more likely to report unprotected sex with an unknown sero-status partner. In this sample of sero-discordant couples we found indication of excess HIV-risk behaviour among men involved in polygynous relationships.

Effect of variable transmission rate on the dynamics of HIV in sub-Saharan Africa

BACKGROUND

The cause of the high HIV prevalence in sub-Saharan Africa is incompletely understood, with heterosexual penile-vaginal transmission proposed as the main mechanism. Heterosexual HIV transmission has been estimated to have a very low probability; but effects of cofactors that vary in space and time may substantially alter this pattern.

METHODS

To test the effect of individual variation in the HIV infectiousness generated by co-infection, we developed and analyzed a mathematical sexual network model that simulates the behavioral components of a population from Malawi, as well as the dynamics of HIV and the co-infection effect caused by other infectious diseases, including herpes simplex virus type-2, gonorrhea, syphilis and malaria.

RESULTS

The analysis shows that without the amplification effect caused by co-infection, no epidemic is generated, and HIV prevalence decreases to extinction. But the model indicates that an epidemic can be generated by the amplification effect on HIV transmission caused by co-infection.

CONCLUSION

The simulated sexual network demonstrated that a single value for HIV infectivity fails to describe the dynamics of the epidemic. Regardless of the low probability of heterosexual transmission per sexual contact, the inclusion of individual variation generated by transient but repeated increases in HIV viral load associated with co-infections may provide a biological basis for the accelerated spread of HIV in sub-Saharan Africa. Moreover, our work raises the possibility that the natural history of HIV in sub-Saharan Africa cannot be fully understood if individual variation in infectiousness is neglected.

Age-disparity, sexual connectedness and HIV infection in disadvantaged communities around Cape Town, South Africa: a study protocol

Background

Crucial connections between sexual network structure and the distribution of HIV remain inadequately understood, especially in regard to the role of concurrency and age disparity in relationships, and how these network characteristics correlate with each other and other risk factors. Social desirability bias and inaccurate recall are obstacles to obtaining valid, detailed information about sexual behaviour and relationship histories. Therefore, this study aims to use novel research methods in order to determine whether HIV status is associated with age-disparity and sexual connectedness as well as establish the primary behavioural and socio-demographic predictors of the egocentric and community sexual network structures.

Method/Design

We will conduct a cross-sectional survey that uses a questionnaire exploring one-year sexual histories, with a focus on timing and age disparity of relationships, as well as other risk factors such as unprotected intercourse and the use of alcohol and recreational drugs. The questionnaire will be administered in a safe and confidential mobile interview space, using audio computer-assisted self-interview (ACASI) technology on touch screen computers. The ACASI features a choice of languages and visual feedback of temporal information. The survey will be administered in three peri-urban disadvantaged communities in the greater Cape Town area with a high burden of HIV. The study communities participated in a previous TB/HIV study, from which HIV test results will be anonymously linked to the survey dataset. Statistical analyses of the data will include descriptive statistics, linear mixed-effects models for the inter- and intra-subject variability in the age difference between sexual partners, survival analysis for correlated event times to model concurrency patterns, and logistic regression for association of HIV status with age disparity and sexual connectedness.

Discussion

This study design is intended to facilitate more accurate recall of sensitive sexual history data and has the potential to provide substantial insights into the relationship between key sexual network attributes and additional risk factors for HIV infection. This will help to inform the design of context-specific HIV prevention programmes.

Effect of concurrent sexual partnerships on rate of new HIV infections in a high-prevalence, rural South African population: a cohort study

BACKGROUND

Concurrent sexual partnerships are widely believed to be one of the main drivers of the HIV epidemic in sub-Saharan Africa. This view is supported by theoretical models predicting that increases in prevalence of concurrent partnerships could substantially increase the rate of spread of the disease. However, the effect of concurrent partnerships on HIV incidence has not been appropriately tested in a sub-Saharan African setting.

METHODS

For this population-based cohort study, we used data from the Africa Centre demographic surveillance site in KwaZulu-Natal, South Africa, to try to find support for the concurrency hypothesis. We used a moving-window approach to construct estimates of the geographical variation in reported concurrent and lifetime partners in sexually active men aged 15-55 years (n=2153) across the study area. We then followed up 7284 HIV-negative women (≥15 years of age) in the population and quantified the effect of the sexual behaviour profiles of men in the surrounding local community on a woman's hazard of HIV acquisition.

FINDINGS

During 5 years' follow-up, 693 new female HIV infections occurred (incidence 3.60 cases per 100 person-years). We identified substantial intercommunity heterogeneity in the estimated point-prevalence of partnership concurrency (range 4.0-76.3%; mean 31.5%) and mean number of lifetime sexual partners (3.4-12.9; mean 6.3) in sexually active men in this population. After adjustment for individual-level sexual behaviour and demographic, socioeconomic, and environmental factors associated with HIV acquisition, mean lifetime number of partners of men in the immediate local community was predictive of hazard of HIV acquisition in women (adjusted hazard ratio [HR] 1.08, 95% CI 1.03-1.14, p=0.004), whereas a high prevalence of partnership concurrency in the same local community was not associated with any increase in risk of HIV acquisition (adjusted HR 1.02, 95% CI 0.95-1.09, p=0.556).

INTERPRETATION

We find no evidence to suggest that concurrent partnerships are an important driver of HIV incidence in this typical high-prevalence rural African population. Our findings suggest that in similar hyperendemic sub-Saharan African settings, there is a need for straightforward, unambiguous messages aimed at the reduction of multiple partnerships, irrespective of whether those partnerships overlap in time.

FUNDING

US National Institute of Child Health and Human Development; Wellcome Trust.

Partner Concurrency and the STD/HIV Epidemic

Conceptually and theoretically, it is easy to see how short gaps and concurrent partnerships fuel the spread of sexually transmitted infections (STI) and HIV in populations. The consequences of concurrency are bounded by the duration of the infectious period and by the relationships between concurrent partnerships and other dimensions of sexual behavior. Consequently, it is difficult to predict how concurrent partnerships or short gaps may be related to the spread of STI and HIV in a particular epidemiologic context in empirical reality. In recent years, analyses of sexual behavior data collected through nationally representative surveys revealed similar prevalences of concurrent sexual partnerships in Western populations. The association between concurrent sexual partnerships and STI/HIV risk is complicated. At the population level, recent findings suggest that the ecological association between polygyny and HIV prevalence is negative at the country level and at the sub-national level. To address the need for agreed-upon standard definitions and measures of concurrent sexual partnerships, which will facilitate comparisons across time and settings, the Joint United Nations Program on HIV/AIDS (UNAIDS) Reference Group on Estimates, Modelling, and Projections convened a meeting in April 2009. The recommendations developed at this meeting include suggestions for a definition, indicators, and measures of concurrency.

Community-level gender equity and extramarital sexual risk-taking among married men in eight African countries

CONTEXT

In many parts of Africa, women are most likely to become infected with HIV by having unprotected sex with their husbands, who may have acquired the virus through extramarital sex. However, the ways in which aspects of community environments-particularly those related to gender equity-shape men's extramarital sexual risk-taking are not well understood.

METHODS

Demographic and Health Survey data from eight African countries (Chad, Ghana, Malawi, Nigeria, Tanzania, Uganda, Zambia and Zimbabwe) were used to examine associations between married men's engaging in risky extramarital sex (i.e., having had both unprotected sex and extramarital sex) and indicators of gender equity and other community characteristics. Separate multilevel logistic regression models that incorporated individual, household and community measures were created for each country.

RESULTS

In five countries, men who lived in communities with more equal ratios of women to men with at least a primary education were less likely to report risky extramarital sexual activity (odds ratios, 0.4-0.6). A similar relationship was found in four countries for the ratio of women to men who were employed (0.4-0.5). In three countries, men who lived in communities with more conservative attitudes toward wife-beating or male decision making had elevated odds of extramarital sexual risk-taking (1.1-1.5).

CONCLUSIONS

While HIV prevention programs should focus on reducing gender inequities, they also need to recognize the conservative cultural factors that influence the formation of men's masculine identities and, in turn, affect their sexual behavior.

Concurrent sexual partnerships and human immunodeficiency virus risk among South African youth

BACKGROUND

To estimate the prevalence of concurrency (more than 1 sex partner overlapping in time), the attitudes/behaviors of those engaged in concurrency, length of relationship overlap, and the association between concurrency and human immunodeficiency virus (HIV) among South Africans aged 15 to 24 years.

METHODS

A cross-sectional, nationally representative, household survey of HIV infection, and sexual attitudes and behaviors was conducted among 11,904 15 to 24 year old South Africans in 2003. Analyses were conducted among sexually experienced youth.

RESULTS

Men were more likely to report having concurrent (24.7%) than serial partners (5.7%) in the past 12 months, but concurrency was not associated with HIV. Among women, concurrency and serial monogamy were equally common (4.7%), and concurrency, defined by respondent reports of multiple ongoing partners, was associated with HIV in multivariate analysis (odds ratio, 3.4; 95% confidence interval, 1.8-6.5). Median length of relationship overlap was approximately 4 months for women and 3 months for men. Compared to serial monogamists, concurrents reported less consistent condom use, and female concurrents were more likely to report transactional sex and problems negotiating condoms and refusing intercourse.

CONCLUSIONS

Concurrency is a common partnership pattern among those youth with multiple partners, especially men. For women, having concurrent relationships may be associated with relationship power imbalances and less ability to protect against HIV. Given the prevalence and likely significance of concurrency in the spread of HIV throughout a sexual network, our findings underscore the need for prevention efforts targeting fidelity.

Multiple recent sexual partnerships and alcohol use among sexually transmitted infection clinic patients, Cape Town, South Africa

BACKGROUND

Multiple recent sex partners promote the rapid spread of sexually transmitted infections (STI), including human immunodeficiency virus. Alcohol use is also closely associated with unprotected sexual behavior, but its use has not been investigated in relation to multiple recent sex partners in southern Africa.

PURPOSE

To examine the combined risks of multiple recent sex partners and alcohol use among people seeking treatment for identified STI in Cape Town, South Africa.

METHODS

Men (n = 529) and women (n = 210) receiving STI clinic services completed anonymous surveys of sexual behaviors and substance use over a two-month retrospective period. Sexual risk was defined by frequencies of unprotected intercourse and drinking alcohol before sexual intercourse.

RESULTS

A total of 264 (31%) participants reported 2 or more sex partners in the previous 2 months; 87% of these partnerships occurred within 1 month of each other. Substantially greater multiple recent partners, including a greater fraction of sexual relationships estimated concurrently, were observed among men than women. Alcohol use was common in the sample, and drinking in sexual contexts was associated with multiple partners. Moderator analyses failed to show that alcohol use played a significant role in unprotected sex with multiple recent partners.

CONCLUSIONS

Multiple recent partners and drinking appear independently related to unprotected sex, and both multiple partners and alcohol use should be targeted in human immunodeficiency virus risk reduction interventions.

Concurrent partnerships and HIV: an inconvenient truth

The strength of the evidence linking concurrency to HIV epidemic severity in southern and eastern Africa led the Joint United Nations Programme on HIV/AIDS and the Southern African Development Community in 2006 to conclude that high rates of concurrent sexual partnerships, combined with low rates of male circumcision and infrequent condom use, are major drivers of the AIDS epidemic in southern Africa. In a recent article in the Journal of the International AIDS Society, Larry Sawers and Eileen Stillwaggon attempt to challenge the evidence for the importance of concurrency and call for an end to research on the topic. However, their "systematic review of the evidence" is not an accurate summary of the research on concurrent partnerships and HIV, and it contains factual errors concerning the measurement and mathematical modelling of concurrency.Practical prevention-oriented research on concurrency is only just beginning. Most interventions to raise awareness about the risks of concurrency are less than two years old; few evaluations and no randomized-controlled trials of these programmes have been conducted. Determining whether these interventions can help people better assess their own risks and take steps to reduce them remains an important task for research. This kind of research is indeed the only way to obtain conclusive evidence on the role of concurrency, the programmes needed for effective prevention, the willingness of people to change behaviour, and the obstacles to change.

What happened to multiple sexual partnerships in Swaziland? Analysis of five linked national surveys between 2002 and 2008

Multiple sexual partnerships are a driver of the HIV epidemic in southern Africa. Five linked cluster surveys in 2002, 2005, 2006, 2007 and 2008 allowed us to measure changes in rates of multiple partnerships in these clusters in Swaziland. We selected a stratified random sample of census enumeration areas in 2002 and survey teams subsequently revisited this same sample (a random sub-sample in 2005 and 2006). For this study, analysis includes only people aged 18-29 years interviewed in communities included in all five surveys (1862 men and 2701 women). Among men, there was a significant fall in the proportion having multiple partners in the last 12 months (MP12), among those that had any, between 2002 (61%) and 2007 (46%), followed by a slight rise in 2008 (49%). For multiple partnerships in the last six months (MP6 - measured in 2005 and 2006), there was a decrease between 2005 (43%) and 2006 (25%). There was a significant decrease in multiple partnerships in the last month (MP1) between 2005 (35%) and 2006 (16%), followed by an increase in 2007 (24%) and 2008 (25%). Among women, there was a significant decrease in MP12 between 2002 (22%) and 2007 (9%), then a significant increase in 2008 (15%). There was little difference in women's MP6 between 2005 (7%) and 2006 (6%). There was also little change in women's MP1 between 2005 (5%) and 2006 (3%), with an increase from 2007 (3%) to 2008 (6%); the 2006-2008 difference was significant. A 2006 campaign to reduce multiple partnerships may have changed behaviour among men or it may have made them less likely to admit to multiple partners. The recent increase in MP12 and MP1, especially among women, may reflect behaviour or it could reflect increased willingness to report.