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 (nonprimary 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

Social Capital, High-Risk Sexual Behaviors, and Sexually Transmitted Infections in Agricultural Plantation Residents in Tanzania

Human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs) are leading causes of mortality and morbidity in many countries of the world. The practice of having concurrent sexual partners is an important risk factor for STI transmission. Social capital is a target area for improving sexual health. Social capital describes the ways in which individuals are connected to resources that can influence their behaviors, and provides methods of coping with stressors. Previous studies have yielded contradicting findings about the effects social capital has on sexual health behaviors and STI prevalence. Our study aims to investigate social factors, namely social capital and support, which may play a role in reducing STI prevalence and the practice of concurrent partnerships. We conducted secondary data analysis from a study of 623 agricultural plantation residents in Tanzania to assess this relationship, hypothesizing that higher social capital would be associated with less concurrent sexual partnerships and less prevalent STIs (including HIV, HSV-2, and syphilis). We used principal component analysis to convert seven variables related to social capital into a smaller set of uncorrelated factors. The resultant 3 factors – reciprocity, trust, and decision-making – were used as predictors in multiple regression models for both concurrent sexual partnerships and prevalent STI, stratified by gender. We found that having positive social capital in the ‘network’ dimension was associated with being less likely to have concurrent sexual partnerships among women (AOR=0.47, 95% CI 0.23-0.87) and that having positive social capital in decision making was associated with being more likely to have a prevalent STI among men (AOR=2.13, 95% CI 1.02-4.52). Transactional sex was significantly associated with both outcomes in women. Suggested initiatives for improvement of sexual health include creating community groups that encourage unity and fellowship among women in order to decrease the prevalence of risky sexual behaviors. More research is necessary to create a uniform definition of social capital that can be applied in future studies that examine the relationship between this concept and sexual health.No embargoAcademic Major: Public Healt

Broadening the Benefits of Dual Enrollment: Reaching Underachieving and Underrepresented Students with Career-Focused Programs

A three-year study tracking outcomes for thousands of students across California shows that careerfocused dual enrollment programs can provide important benefits for those who are underachieving and underrepresented in higher education. Programs of this type, which allow high school students to take college courses and earn college credit, were once offered almost exclusively to high-achieving students seeking greater academic challenge

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

Different Approaches to Dual Enrollment: Understanding Program Features and Their Implications

Examines program features, challenges, and benefits of secondary-postsecondary partnerships that allow high school students to take college courses for credit, with a career-focused strategy for engaging underperforming students. Includes recommendations

Concurrent partnerships in Cape Town, South Africa : race and sex differences in prevalence and duration of overlap

Introduction: Concurrent partnerships (CPs) have been suggested as a risk factor for transmitting HIV, but their impact on the epidemic depends upon how prevalent they are in populations, the average number of CPs an individual has and the length of time they overlap. However, estimates of prevalence of CPs in Southern Africa vary widely, and the duration of overlap in these relationships is poorly documented. We aim to characterize concurrency in a more accurate and complete manner, using data from three disadvantaged communities of Cape Town, South Africa. Methods: We conducted a sexual behaviour survey (n = 878) from June 2011 to February 2012 in Cape Town, using Audio Computer-Assisted Self-Interviewing to collect sexual relationship histories on partners in the past year. Using the beginning and end dates for the partnerships, we calculated the point prevalence, the cumulative prevalence and the incidence rate of CPs, as well as the duration of overlap for relationships begun in the previous year. Linear and binomial regression models were used to quantify race (black vs. coloured) and sex differences in the duration of overlap and relative risk of having CPs in the past year. Results: The overall point prevalence of CPs six months before the survey was 8.4%: 13.4% for black men, 1.9% for coloured men, 7.8% black women and 5.6% for coloured women. The median duration of overlap in CPs was 7.5 weeks. Women had less risk of CPs in the previous year than men (RR 0.43; 95% CI: 0.32-0.57) and black participants were more at risk than coloured participants (RR 1.86; 95% CI: 1.17-2.97). Conclusions: Our results indicate that in this population the prevalence of CPs is relatively high and is characterized by overlaps of long duration, implying there may be opportunities for HIV to be transmitted to concurrent partners

Trends in Concurrency, Polygyny, and Multiple Sex Partnerships During a Decade of Declining HIV Prevalence in Eastern Zimbabwe.

Background. Observed declines in the prevalence of human immunodeficiency virus (HIV) infection in Zimbabwe have been attributed to population-level reductions in sexual partnership numbers. However, it remains unknown whether certain types of sex partnerships were more important to this decline. Particular debate surrounds the epidemiologic importance of polygyny (the practice of having multiple wives). Methods. We analyze changes in reported multiple partnerships, nonmarital concurrency, and polygyny in eastern Zimbabwe during a period of declining HIV prevalence, from 1998 to 2011. Trends are reported for adult men (age, 17–54 years) and women (age, 15–49 years) from 5 survey rounds of the Manicaland HIV/STD Prevention Project, a general-population open cohort study. Results. At baseline, 34.2% of men reported multiple partnerships, 11.9% reported nonmarital concurrency, and 4.6% reported polygyny. Among women, 4.6% and 1.8% reported multiple partnerships and concurrency, respectively. All 3 partnership indicators declined by similar relative amounts (around 60%–70%) over the period. Polygyny accounted for around 25% of male concurrency. Compared with monogamously married men, polygynous men reported higher levels of subsequent divorce/separation (adjusted relative risk [RR], 2.92; 95% confidence interval [CI], 1.87–4.55) and casual sex partnerships (adjusted RR, 1.63; 95% CI, 1.41–1.88). Conclusions. No indicator clearly dominated declines in partnerships. Polygyny was surprisingly unstable and, in this population, should not be considered a safe form of concurrency

Demographic and Behavioural Factors in Tanzanian and Norwegian Patients with Sexually Transmitted Infections.

To evaluate whether differences in demographic or behavioural factors might explain differences in reported or diagnosed sexually transmitted infections (STI), we have compared data from 1097 Tanzanian and Norwegian STI patients. Most demographic data were similar, whereas some behavioural data differed. Norwegian patients reported significantly higher numbers of sexual partners than Tanzanian. Thirty-three percent of Tanzanian patients tested positive for HIV antibodies, females more often (43%) than males (26%). Approximately one-third and two-thirds of the female HIV-positive Tanzanian STI patients had already seroconverted at the age of 25 and 30 years, respectively. The national differences encountered probably reflect cultural differences, different panoramas of STI and a lower accessibility to optimal health services in Tanzania. Lack of expected statistical associations between some of the data in the Tanzanian STI group might question the validity of the retrospectively collected data in this group, or indicate that questions not included in the questionnaire might be of importance

Understanding HIV/AIDS in the African Context

This book of readings is intended for courses in Global Health. The editors asked Prof. Stillwaggon to contribute a chapter summarizing her years of work on the spread of HIV/AIDS in populations among whom bacterial, fungal, parasitic, and viral diseases are extremely common, particularly in sub-Saharan Africa. Her work has demonstrated that differences in behavior cannot explain differences in HIV rates between world regions

Sexual behaviour patterns in South Africa and their association with the spread of HIV: insights from a mathematical model

This paper aims to quantify the effects of different types of sexual risk behaviour on the spread of HIV in South Africa. A mathematical model is developed to simulate changes in numbers of sexual partners, changes in marital status, changes in commercial sex activity and changes in the frequency of unprotected sex over the life course. This is extended to allow for the transmission of HIV, and the model is fitted to South African HIV prevalence data and sexual behaviour data. Results suggest that concurrent partnerships and other non-spousal partnerships are major drivers of the HIV/AIDS epidemic in South Africa.AIDS/HIV, sexual behavior, simulation model, South Africa