Polygyny and the spread of HIV in sub-Saharan Africa: a case of benign concurrency

HIV and concurrent sexual partnerships: modelling the role of coital dilution

BACKGROUND

The concurrency hypothesis asserts that high prevalence of overlapping sexual partnerships explains extraordinarily high HIV levels in sub-Saharan Africa. Earlier simulation models show that the network effect of concurrency can increase HIV incidence, but those models do not account for the coital dilution effect (non-primary partnerships have lower coital frequency than primary partnerships).

METHODS

We modify the model of Eaton et al (AIDS and Behavior, September 2010) to incorporate coital dilution by assigning lower coital frequencies to non-primary partnerships. We parameterize coital dilution based on the empirical work of Morris et al (PLoS ONE, December 2010) and others. Following Eaton et al, we simulate the daily transmission of HIV over 250 years for 10 levels of concurrency.

RESULTS

At every level of concurrency, our focal coital-dilution simulation produces epidemic extinction. Our sensitivity analysis shows that this result is quite robust; even modestly lower coital frequencies in non-primary partnerships lead to epidemic extinction.

CONCLUSIONS

In order to contribute usefully to the investigation of HIV prevalence, simulation models of concurrent partnering and HIV epidemics must incorporate realistic degrees of coital dilution. Doing so dramatically reduces the role that concurrency can play in accelerating the spread of HIV and suggests that concurrency cannot be an important driver of HIV epidemics in sub-Saharan Africa. Alternative explanations for HIV epidemics in sub-Saharan Africa are needed.

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.

Concurrent sexual partnerships and associated factors: a cross-sectional population-based survey in a rural community in Africa with a generalised HIV epidemic

Background

Although concurrent sexual partnerships may play an important role in HIV transmission in Africa, the lack of an agreed definition of concurrency and of standard methodological approaches has hindered studies. In a long-standing general population cohort in rural Uganda we assessed the prevalence of concurrency and investigated its association with sociodemographic and behavioural factors and with HIV prevalence, using the new recommended standard definition and methodological approaches.

Methods

As part of the 2010 annual cohort HIV serosurvey among adults, we used a structured questionnaire to collect information on sociodemographic and behavioural factors and to measure standard indicators of concurrency using the recommended method of obtaining sexual-partner histories. We used logistic regression to build a multivariable model of factors independently associated with concurrency.

Results

Among those eligible, 3,291 (66%) males and 4,052 (72%) females participated in the survey. Among currently married participants, 11% of men and 25% of women reported being in a polygynous union. Among those with a sexual partner in the past year, the proportion reporting at least one concurrent partnership was 17% in males and 0.5% in females. Polygyny accounted for a third of concurrency in men and was not associated with increased HIV risk. Among men there was no evidence of an association between concurrency and HIV prevalence (but too few women reported concurrency to assess this after adjusting for confounding). Regarding sociodemographic factors associated with concurrency, females were significantly more likely to be younger, unmarried, and of lower socioeconomic status than males. Behavioural factors associated with concurrency were young age at first sex, increasing lifetime partners, and a casual partner in the past year (among men and women) and problem drinking (only men).

Conclusions

Our findings based on the new standard definition and methodological approaches provide a baseline for measuring changes in concurrency and HIV incidence in future surveys, and a benchmark for other studies. As campaigns are now widely conducted against concurrency, such surveys and studies are important in evaluating their effectiveness in decreasing HIV transmission.

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.

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.

The reliability of sexual partnership histories: implications for the measurement of partnership concurrency during surveys

OBJECTIVES

To measure the reliability of sexual partnership histories collected during survey interviews and to assess the impact of measurement error on survey estimates of partnership concurrency.

METHODS

We used sociocentric data collected on Likoma Island (Malawi). Up to five of the respondents' most recent sexual partners were identified in population rosters. We assessed interpartner agreement (IPA) in reports of sexual partnerships (i.e. whether partners concordantly report that they have had sexual relations with each other) and its association with respondent and partnership characteristics. We estimated the extent of bias in the point prevalence of concurrency and the duration of overlap between concurrent partnerships according to two scenarios: one in which only partnerships reported by both partners were considered as 'true' ('concordant scenario'), and one in which partnerships reported by either partner were included ('complete scenario').

FINDINGS

IPA was low in nonmarital relations, but was significantly higher in ongoing than in dissolved nonmarital relations. IPA was further associated with the number of other partners the respondents or their partner(s) had, as well as with the duration of ongoing partnerships. Biases in measurements of the prevalence of concurrent partnerships were large: concurrent partnerships were rare in the concordant scenario, but common in the complete scenario. This was particularly true among never married women. Estimates of the average duration of overlap between concurrent partnerships derived from self-reported survey data were also biased, particularly among married respondents.

CONCLUSION

Future empirical tests of the 'concurrency hypothesis' and interventions targeting concurrent partnerships should take reporting biases into account.

Timing is everything: international variations in historical sexual partnership concurrency and HIV prevalence

BACKGROUND

Higher prevalence of concurrent partnerships is one hypothesis for the severity of the HIV epidemic in the countries of Southern Africa. But measures of the prevalence of concurrency alone do not adequately capture the impact concurrency will have on transmission dynamics. The importance of overlap duration and coital exposure are examined here.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a comparison of data from three studies of sexual behavior carried out in the early 1990s in Uganda, Thailand and the US. Using cumulative concurrency measures, the three countries appeared somewhat similar. Over 50% of both Thai and Ugandan men reported a concurrency within the last three partnerships and over 20% reported a concurrency in the last year, the corresponding rates among US men were nearly 20% for Blacks and Hispanics, and about 10% for other racial/ethnic groups. Concurrency measures that were more sensitive to overlap duration, however, showed large differences. The point prevalence of concurrency on the day of interview was over 10% among Ugandan men compared to 1% for Thai men. Ugandan concurrencies were much longer duration - a median of about two years - than either the Thai (1 day) or US concurrencies (4-9 months across all groups), and involved 5-10 times more coital risk exposure with the less frequent partner. In the US, Blacks and Hispanics reported higher prevalence, longer duration and greater coital exposure than Whites, but were lower than Ugandans on nearly every measure. Together, the differences in the prevalence, duration and coital exposure of concurrent partnerships observed align with the HIV prevalence differentials seen in these populations at the time the data were collected.

CONCLUSIONS/SIGNIFICANCE

There were substantial variations in the patterns of concurrent partnerships within and between populations. More long-term overlapping partnerships, with regular coital exposure, were found in populations with greater HIV epidemic severity.

In the absence of marriage: long-term concurrent partnerships, pregnancy, and HIV risk dynamics among South African young adults

In KwaZulu/Natal, South Africa, where HIV prevalence is among the world's highest, a longitudinal qualitative study of partnership dynamics and HIV preventive behaviors was conducted. 47 young adults aged 18-24 participated in in-depth interviews, and 29 were re-interviewed 2 years later. Five analytical domains emerged: primary partnerships, love and romance; secondary partnerships; pregnancy/parenthood; condom use/prevention; and contextual influences, including schooling and future aspirations. Primary relationships were long-lasting, with most men and women in the same relationship at 2-year follow-up. Secondary, casual partnerships were common for men and women, although these were shorter and changed frequently. Love and marriage aspirations were not viewed as incompatible with secondary partners. Condom use increased over time in some primary relationships, but decreased in others, and was nearly universal with non-primary partners. Pregnancy, school drop-out, and economic need strongly influence young people's lifecourse. These findings suggest the need to focus prevention efforts on the partnership context, including partner reduction, and structural factors that impede or enhance prevention success.

Concurrent sexual partnerships do not explain the HIV epidemics in Africa: a systematic review of the evidence

The notion that concurrent sexual partnerships are especially common in sub-Saharan Africa and explain the region's high HIV prevalence is accepted by many as conventional wisdom. In this paper, we evaluate the quantitative and qualitative evidence offered by the principal proponents of the concurrency hypothesis and analyze the mathematical model they use to establish the plausibility of the hypothesis.We find that research seeking to establish a statistical correlation between concurrency and HIV prevalence either finds no correlation or has important limitations. Furthermore, in order to simulate rapid spread of HIV, mathematical models require unrealistic assumptions about frequency of sexual contact, gender symmetry, levels of concurrency, and per-act transmission rates. Moreover, quantitative evidence cited by proponents of the concurrency hypothesis is unconvincing since they exclude Demographic and Health Surveys and other data showing that concurrency in Africa is low, make broad statements about non-African concurrency based on very few surveys, report data incorrectly, report data from studies that have no information about concurrency as though they supported the hypothesis, report incomparable data and cite unpublished or unavailable studies. Qualitative evidence offered by proponents of the hypothesis is irrelevant since, among other reasons, there is no comparison of Africa with other regions.Promoters of the concurrency hypothesis have failed to establish that concurrency is unusually prevalent in Africa or that the kinds of concurrent partnerships found in Africa produce more rapid spread of HIV than other forms of sexual behaviour. Policy makers should turn attention to drivers of African HIV epidemics that are policy sensitive and for which there is substantial epidemiological evidence.