Measuring concurrency: an empirical study of different methods in a large population-based survey and evaluation of the UNAIDS guidelines

Comparing Sexual Network Mean Active Degree Measurement Metrics Among Men Who Have Sex With Men

BACKGROUND

Mean active degree is an important proxy measure of cross-sectional network connectivity commonly used in HIV/sexually transmitted infection epidemiology research. No current studies have compared measurement methods of mean degree using a cross-sectional study design for men who have sex with men (MSM) in the United States. We compared mean degree estimates based on reported ongoing main and casual sexual partnerships (current method) against dates of first and last sex (retrospective method).

METHODS

We used data from ARTnet, a cross-sectional survey of MSM in the United States (2017-2019). ARTnet collected data on the number and types of sexual partners in the past year, limited to the 5 most recent partners (data truncation). We quantified partnerships for months 0 to 12 before the survey date (retrospective method) and compared that with ongoing partnerships on the day of survey (current method). We used linear regression to understand the impact of truncated partnership data on mean degree estimation.

RESULTS

The retrospective method yielded similar degree estimates to the current for months proximate to the day of survey. The retrospective method mean degree systematically decreased as the month increased from 0 to 12 months before survey date. This was driven by data truncation: among participants with >5 partners in the past year compared with those with ≤5, the average change in main partnership degree between 12 and 0 months before survey date was -0.05 (95% confidence interval, -0.08 to -0.03) after adjusting for race/ethnicity, age, and education. The adjusted average change in casual partnership degree was -0.40 (95% confidence interval, -0.45 to -0.35).

CONCLUSIONS

The retrospective method underestimates mean degree for MSM in surveys with truncated partnership data, especially for casual partnerships. The current method is less prone to bias from partner truncation when the target population has high rate of partners per year.

Assessment of Bias in Estimates of Sexual Network Degree using Prospective Cohort Data

BACKGROUND

Sexual network degree, a count of ongoing partnerships, plays a critical role in the transmission dynamics of human immunodeficiency virus and other sexually transmitted infections. Researchers often quantify degree using self-reported cross-sectional data on the day of survey, which may result in bias because of uncertainty about future sexual activity.

METHODS

We evaluated the bias of a cross-sectional degree measure with a prospective cohort study of men who have sex with men (MSM). At baseline, we asked men about whether recent sexual partnerships were ongoing. We confirmed the true, ongoing status of those partnerships at baseline at follow-up. With logistic regression, we estimated the partnership-level predictors of baseline measure accuracy. With Poisson regression, we estimated the longitudinally confirmed degree as a function of baseline predicted degree.

RESULTS

Across partnership types, the baseline ongoing status measure was 70% accurate, with higher negative predictive value (91%) than positive predictive value (39%). Partnership exclusivity and racial pairing were associated with higher accuracy. Baseline degree generally overestimated confirmed degree. Bias, or number of ongoing partners different than predicted at baseline, was -0.28 overall, ranging from -1.91 to -0.41 for MSM with any ongoing partnerships at baseline. Comparing MSM of the same baseline degree, the level of bias was stronger for black compared with white MSM, and for younger compared with older MSM.

CONCLUSIONS

Research studies may overestimate degree when it is quantified cross-sectionally. Adjustment and structured sensitivity analyses may account for bias in studies of human immunodeficiency virus or sexually transmitted infection prevention interventions.

Sexual Concurrency and Contraceptive Use Among Young Adult Women

Leveraging 2.5 years of weekly data from the Relationship Dynamics and Social Life Study, we investigate the relationship between young women's sexual concurrency and their contraceptive behavior. Specifically, we (1) examine whether young women changed their contraceptive use when switching from one to multiple concurrent sexual partners in the same week; (2) explore the uniformity of contraceptive responses to concurrency across relationship context; and (3) compare the contraceptive behaviors of never-concurrent women with those of ever-concurrent women in weeks when they were not concurrent. Nearly one in five sexually active young women had sex with two or more people in the same week. When they were concurrent, these women's odds of using any contraception increased threefold, and their odds of using condoms increased fourfold. This pattern of contraceptive adjustments was the same across relationship characteristics, such as duration and exclusivity. Yet when they were not concurrent, ever-concurrent women were less likely to use any contraception and used condoms less consistently than women who were never concurrent. We discuss these findings in the context of ongoing debates about the role of sexual concurrency in STI transmission dynamics.

Sexual Networks of Racially Diverse Young MSM Differ in Racial Homophily But Not Concurrency

BACKGROUND

Substantial racial disparities exist in HIV infection among young men who have sex with men (YMSM). However, evidence suggests black YMSM do not engage in greater levels of risk behavior. Sexual networks may help explain this paradox. This study used egocentric exponential random graph models to examine variation in concurrency (ie, 2 or more simultaneous partners) and homophily (ie, same race/ethnicity partners) across race/ethnicity groups in a diverse sample of YMSM.

METHODS

Data for this study come from a longitudinal cohort study of YMSM. Participants (n = 1012) provided data regarding their sexual contacts during the 6 months before their first study visit. A series of egocentric exponential random graph models examined how providing separate estimates for homophily and concurrency parameters across race/ethnicity improved the fit of these models. Networks were simulated using these parameters to examine how local network characteristics impact risk at the whole network level.

RESULTS

Results indicated that homophily, but not concurrency, varied across race/ethnicity. Black participants witnessed significantly higher race/ethnicity homophily compared with white and Latino peers. Extrapolating from these models, black individuals were more likely to be in a connected component with an HIV-positive individual and closer to HIV-positive individuals. However, white individuals were more likely to be in large connected components.

CONCLUSIONS

These findings suggest that high racial homophily combined with existing disparities in HIV help perpetuate the spread of HIV among black YMSM. Nonetheless, additional work is required to understand these disparities given that homophily alone cannot sustain them indefinitely.

But Everyone is Doing It (Sort of)! Perceived Sexual Risks in the Social Environment and the Impact on Homeless Youth Engagement in Concurrent Sexual Relationships

Although homeless youth are likely to engage in concurrent sexual relationships and doing so can accelerate HIV transmission, the issue of sexual concurrency (i.e., having sexual partnerships that overlap in time) has received scarce attention in this vulnerable population. The literature that exists tends to focus on individuals' characteristics that may be associated with concurrency and overlooks the influence of their social environment. Informed by the risk amplification and abatement model (RAAM), this study explored the association between pro-social and problematic social network connections, and sexual concurrency among homeless youth using drop-in center services (N = 841). Nearly 37% of youth engaged in concurrency. Partially consistent with the RAAM, regression analyses showed that affiliation with more problematic ties (i.e., having more network members who practice concurrency and unprotected sex) was associated with greater sexual concurrency. Programs addressing HIV risk among homeless youth in drop-in centers should consider the role youths' network composition may play in concurrency.

Implicit attitudes to sexual partner concurrency vary by sexual orientation but not by gender-A cross sectional study of Belgian students

High rates of sexual partner concurrency have been shown to facilitate the spread of various sexually transmitted infections. Assessments of explicit attitudes to concurrency have however found little difference between populations. Implicit attitudes to concurrency may vary between populations and play a role in generating differences in the prevalence of concurrency. We developed a concurrency implicit associations test (C-IAT) to assess if implicit attitudes towards concurrency may vary between individuals and populations and what the correlates of these variations are. A sample of 869 Belgian students (mean age 23, SD 5.1) completed an online version of the C-IAT together with a questionnaire concerning sexual behavior and explicit attitudes to concurrency. The study participants C-IATs demonstrated a strong preference for monogamy (-0.78, SD = 0.41). 93.2% of participants had a pro-monogamy C-IAT. There was no difference in this implicit preference for monogamy between heterosexual men and women. Men who have sex with men and women who have sex with women were more likely to exhibit implicit but not explicit preferences for concurrency compared to heterosexual men and women. Correlates of the C-IAT varied between men and women.

Concurrency and other sexual partnership patterns reported in a survey of young people in rural Northern Tanzania

African adolescents and young adults remain at substantial risk of infection with HIV and other sexually transmitted infections (STIs), and AIDS is the leading cause of death among African adolescents (10–19 years). Sexual partnership patterns influence transmission risk of sexually transmitted infections. We describe patterns reported by youth (15-30y) in a community-based survey in Tanzania. Among participants reporting multiple partners, we investigated factors associated with reported concurrency. Female (N = 6513) and male (N = 7301) participants had median ages of 21 and 22 years, respectively. Most participants (92%) reported having previously been sexually active, of whom 15% of males and <1% of females reported ≥4 partners in the past year. The point prevalence of concurrency was 2.3% (95%CI 1.9–2.9) for females and 10.6% (95%CI 9.3–12.1) for males. High levels of multiple and concurrent partnerships were reported by those previously married. Females were more likely than males to report having spousal/regular partners and longer partnership lengths. Compared to males, the partnerships reported by females were less likely to be new partnerships, and more likely to be defined by the respondent as still ‘ongoing’. Females reporting younger sexual debut were more likely to report concurrent sexual partners. Far fewer young women reported multiple and concurrent partnerships, but we cannot definitively conclude that concurrency was uncommon for women, because stigma towards women’s multiple sexual partnerships might contribute to substantial under-reporting, as was found in extensive qualitative research in the study population. This study provides one of the most comprehensive quantitative descriptions of partnership patterns of young people in an African setting. Interventions addressing sexual risk among youth should involve male partners, empower women to protect themselves within different types of partnerships, and encourage a greater openness about young people’s sexual relationships.

Gender asymmetry in concurrent partnerships and HIV prevalence

The structure of the sexual network of a population plays an essential role in the transmission of HIV. Concurrent partnerships, i.e. partnerships that overlap in time, are important in determining this network structure. Men and women may differ in their concurrent behavior, e.g. in the case of polygyny where women are monogamous while men may have concurrent partnerships. Polygyny has been shown empirically to be negatively associated with HIV prevalence, but the epidemiological impacts of other forms of gender-asymmetric concurrency have not been formally explored. Here we investigate how gender asymmetry in concurrency, including polygyny, can affect the disease dynamics. We use a model for a dynamic network where individuals may have concurrent partners. The maximum possible number of simultaneous partnerships can differ for men and women, e.g. in the case of polygyny. We control for mean partnership duration, mean lifetime number of partners, mean degree, and sexually active lifespan. We assess the effects of gender asymmetry in concurrency on two epidemic phase quantities (R₀ and the contribution of the acute HIV stage to R₀) and on the endemic HIV prevalence. We find that gender asymmetry in concurrent partnerships is associated with lower levels of all three epidemiological quantities, especially in the polygynous case. This effect on disease transmission can be attributed to changes in network structure, where increasing asymmetry leads to decreasing network connectivity.

Measuring concurrency using a joint multistate and point process model for retrospective sexual history data

Understanding the impact of concurrency, defined as overlapping sexual partnerships, on the spread of HIV within various communities has been complicated by difficulties in measuring concurrency. Retrospective sexual history data consisting of first and last dates of sexual intercourse for each previous and ongoing partnership is often obtained through use of cross-sectional surveys. Previous attempts to empirically estimate the magnitude and extent of concurrency among these surveyed populations have inadequately accounted for the dependence between partnerships and used only a snapshot of the available data. We introduce a joint multistate and point process model in which states are defined as the number of ongoing partnerships an individual is engaged in at a given time. Sexual partnerships starting and ending on the same date are referred to as one-offs and modeled as discrete events. The proposed method treats each individual's continuation in and transition through various numbers of ongoing partnerships as a separate stochastic process and allows the occurrence of one-offs to impact subsequent rates of partnership formation and dissolution. Estimators for the concurrent partnership distribution and mean sojourn times during which a person has k ongoing partnerships are presented. We demonstrate this modeling approach using epidemiological data collected from a sample of men having sex with men and seeking HIV testing at a Los Angeles clinic. Among this sample, the estimated point prevalence of concurrency was higher among men later diagnosed HIV positive. One-offs were associated with increased rates of subsequent partnership dissolution. Copyright © 2016 John Wiley & Sons, Ltd.

On the road again: concurrency and condom use among Uganda truck drivers

Long-distance truck drivers have been shown to be a critical population in the spread of HIV in Africa. In 2009, surveys with 385 Ugandan long-distance truck drivers measured concurrency point prevalence with two methods; it ranged from 37.4% (calendar-method) to 50.1% (direct question). The majority (84%) of relationships reported were long-term resulting in a long duration of overlap (average of 58 months) across concurrent partnerships. Only 7% of these men reported using any condoms with their spouses during the past month. Among all non-spousal relationships, duration of relationship was the factor most strongly associated with engaging in unprotected sex in the past month in a multivariable analyses controlling for partner and relationship characteristics. Innovative intervention programs for these men and their partners are needed that address the realities of truck drivers' lifestyles.

Ecological association between HIV and concurrency point-prevalence in South Africa's ethnic groups

HIV prevalence between different ethnic groups within South Africa exhibits considerable variation. Numerous authors believe that elevated sexual partner concurrency rates are important in the spread of HIV. Few studies have, however, investigated if differential concurrency rates could explain differential HIV spread within ethnic groups in South Africa. This ecological analysis, explores how much of the variation in HIV prevalence by ethnic group is explained by differential concurrency rates. Using a nationally representative survey (the South African National HIV Prevalence, HIV Incidence, Behaviour and Communication Survey, 2005) the HIV prevalence in each of eight major ethnic groups was calculated. Linear regression analysis was used to assess the association between an ethnic group's HIV prevalence and the point-prevalence of concurrency. Results showed that HIV prevalence rates varied considerably between South Africa's ethnic groups. This applied to both different racial groups and to different ethnic groups within the black group. The point-prevalence of concurrency by ethnic group was strongly associated with HIV prevalence (R(2) = 0.83; p = 0.001). Tackling the key drivers of high HIV transmission in this population may benefit from more emphasis on partner reduction interventions.

Concurrency can drive an HIV epidemic by moving R0 across the epidemic threshold

OBJECTIVE

The objective of this study is to investigate whether concurrency can drive an HIV epidemic by moving R0 across the epidemic threshold.

DESIGN AND METHODS

We use a mathematical framework for a dynamic partnership network and the spread of a one-stage infection to study how concurrency is related to the basic reproduction number R0. Two concurrency indices were used to measure the level of concurrency. The model allows varying the level of concurrency in the population, while other key network properties such as partnership duration and lifetime number of partners are kept fixed. In this way, the effect of concurrency on R0 is investigated as an isolated phenomenon.

RESULTS

We find that an increase in concurrency is associated with an increase of R0. For plausible parameter sets for MSM populations, R0 is always above the epidemic threshold of 1. For scenarios that are plausible for sub-Saharan African populations, we show that increasing the level of concurrency can lead to R0 crossing the epidemic threshold. This occurs already at low levels of concurrency. Only a slight shift of the network structure from a purely monogamous population to one wherein individuals are allowed to have at most two partners is enough for this to happen.

CONCLUSION

Concurrency can be a driver of an HIV epidemic in sub-Saharan Africa for low levels of concurrency, although it is not decisive in MSM populations. A small increase in the level of concurrency can lead to R0 crossing the epidemic threshold in a sub-Saharan African setting.

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.

Prevalence and predictors of concurrent sexual partnerships in a predominantly African American population in Jackson, Mississippi

Concurrent sexual partnerships, or sexual partnerships that overlap in time, have been associated with HIV and sexually transmitted infections (STI). How best to measure concurrency and the personal characteristics and predictors of concurrency are not yet well understood. We compared two frequently used concurrency definitions, including a self-reported measure based on participant response regarding overlapping sex with partners, and the UNAIDS measure based on overlapping dates of last sex and intention to have sex again. We performed multivariable logistic regression analyses to identify socio-demographic, behavioral, and structural predictors of concurrency among 1,542 patients at an urban STI clinic in Jackson, Mississippi. Nearly half (44 %) reported concurrency based on self-reported sex with other partners, and 26 % reported concurrency according to the UNAIDS concurrency measure. Using the self-reported concurrency measure, the strongest predictors of concurrency were perceived partner concurrency, drug use at last sex, having more than 10 lifetime partners, and being recently incarcerated. Strongest predictors of concurrency using the UNAIDS measure were lifetime number of partners and perceived partner concurrency. Concurrency is highly prevalent in this population in the Deep South and social, structural and behavioral factors were important predictors of concurrency for both measures. Future research should use time anchored data collection methods and biomarkers to assess whether both definitions of concurrency are associated with HIV outcomes.

Assessment of a new web-based sexual concurrency measurement tool for men who have sex with men

BACKGROUND

Men who have sex with men (MSM) are the most affected risk group in the United States' human immunodeficiency virus (HIV) epidemic. Sexual concurrency, the overlapping of partnerships in time, accelerates HIV transmission in populations and has been documented at high levels among MSM. However, concurrency is challenging to measure empirically and variations in assessment techniques used (primarily the date overlap and direct question approaches) and the outcomes derived from them have led to heterogeneity and questionable validity of estimates among MSM and other populations.

OBJECTIVE

The aim was to evaluate a novel Web-based and interactive partnership-timing module designed for measuring concurrency among MSM, and to compare outcomes measured by the partnership-timing module to those of typical approaches in an online study of MSM.

METHODS

In an online study of MSM aged ≥18 years, we assessed concurrency by using the direct question method and by gathering the dates of first and last sex, with enhanced programming logic, for each reported partner in the previous 6 months. From these methods, we computed multiple concurrency cumulative prevalence outcomes: direct question, day resolution / date overlap, and month resolution / date overlap including both 1-month ties and excluding ties. We additionally computed variants of the UNAIDS point prevalence outcome. The partnership-timing module was also administered. It uses an interactive month resolution calendar to improve recall and follow-up questions to resolve temporal ambiguities, combines elements of the direct question and date overlap approaches. The agreement between the partnership-timing module and other concurrency outcomes was assessed with percent agreement, kappa statistic (κ), and matched odds ratios at the individual, dyad, and triad levels of analysis.

RESULTS

Among 2737 MSM who completed the partnership section of the partnership-timing module, 41.07% (1124/2737) of individuals had concurrent partners in the previous 6 months. The partnership-timing module had the highest degree of agreement with the direct question. Agreement was lower with date overlap outcomes (agreement range 79%-81%, κ range .55-.59) and lowest with the UNAIDS outcome at 5 months before interview (65% agreement, κ=.14, 95% CI .12-.16). All agreements declined after excluding individuals with 1 sex partner (always classified as not engaging in concurrency), although the highest agreement was still observed with the direct question technique (81% agreement, κ=.59, 95% CI .55-.63). Similar patterns in agreement were observed with dyad- and triad-level outcomes.

CONCLUSIONS

The partnership-timing module showed strong concurrency detection ability and agreement with previous measures. These levels of agreement were greater than others have reported among previous measures. The partnership-timing module may be well suited to quantifying concurrency among MSM at multiple levels of analysis.

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.

The role of relationship types on condom use among urban men with concurrent partners in Ghana and Tanzania

Multiple concurrent partnerships are hypothesized to be important drivers of HIV transmission. Despite the demonstrated importance of relationship type (i.e., wife, girlfriend, casual partner, sex worker) on condom use, research on concurrency has not examined how different combinations of relationship types might affect condom use. We address this gap, using survey data from a sample of men from Ghana (GH: n = 807) and Tanzania (TZ: n = 800) who have at least three sexual partners in the past three months. We found that approximately two-thirds of men's reported relationships were classified as a girlfriend. Men were more likely to use a condom with a girlfriend if their other partner was a wife compared to if their other partner was a sex worker (GH: OR 3.10, 95% CI, 1.40, 6.86; TZ: OR 2.34, 95% CI 1.35, 4.06). These findings underscore the importance of considering relationship type when designing HIV prevention strategies in these settings.

Prevalence and correlates of sexual partner concurrency among Australian gay men aged 18-39 years

Mathematical models predict higher rates of HIV and sexually transmitted infections (STIs) in populations with higher rates of concurrent sexual partnerships. Although gay men and other men who have sex with men (MSM) have disproportionately high rates of HIV/STIs, little is known about the prevalence and correlates of sexual concurrency in these populations. This paper reports findings from a national community-based survey of 1,034 Australian gay-identified men aged 18-39 years, who gave detailed information about their sexual partners over the past 12 months. In all, 237 (23 %) reported two or more concurrent sexual partners. For their most recent period of concurrency, 44 % reported three or more partners and 66 % reported unprotected sex with one or more of their partners. A multivariate logistic regression found sexual concurrency was significantly more likely among men on higher incomes (P = 0.02), who first had anal sex at a relatively young age (P = 0.03), and who reported a large number of partners in the past 12 months (P < 0.001). Age, education, HIV status, and other sociodemographic and sexual behavior variables were not significant correlates. However, men who reported sexual concurrency were significantly more likely to have been diagnosed with an STI in the past 12 months (P = 0.04). Findings from this study suggest sexual concurrency is common among younger Australian gay men. With many of these men not always using condoms, health agencies should consider the potential impact of concurrency on HIV/STI epidemics among gay men and other MSM.

A cross-sectional survey of prevalence and correlates of couple sexual concurrency among married couples in fishing communities along Lake Victoria in Kisumu, Kenya

OBJECTIVE

Sexual concurrency has been associated with HIV infection. Since HIV in sub-Saharan Africa is mostly spread within the context of heterosexual couples, it is necessary that intervention is focused on such couples. We sought to establish the correlates of couple sexual concurrency in Kisumu, Kenya.

METHODS

We conducted 1090 gender-matched interviews in 545 couples in a cross-sectional survey. A random sample of fishermen and their spouses from 33 fish-landing beaches along the shores of Lake Victoria in Kisumu were asked to enrol in the study. Couples were separated into different private rooms for simultaneous interviews that documented socioeconomic and behavioural characteristics, and information on number of sexual partnerships in the preceding 6 months and their status. Based on reported concurrency status of the spouses, a couple was categorised as either concurrent when at least one spouse reported a concurrent sexual relationship or non-concurrent.

RESULTS

Overall, 32.1% of the men and 6.2% of the women had concurrent sexual relationships in the 6 months preceding the study, resulting in 37.6% of the couples being sexually concurrent. Unmet sexual desire, intra-spousal suspicions of infidelity, male dominance scripts, domestic violence, couples' children and women's age were the correlates of couple sexual concurrency.

CONCLUSIONS

Unmet sexual desires, inter-spousal infidelity suspicions, male dominance scripts and domestic violence were the main correlates of couple sexual concurrency in these fishing communities.

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.

Partnership concurrency and coital frequency

National HIV prevalence estimates across sub-Saharan Africa range from less than 1 percent to over 25 percent. Recent research proposes several explanations for the observed variation, including prevalence of male circumcision, levels of condom use, presence of other sexually transmitted infections, and practice of multiple concurrent partnerships. However, the importance of partnership concurrency for HIV transmission may depend on how it affects coital frequency with each partner. The coital dilution hypothesis suggests that coital frequency within a partnership declines with the addition of concurrent partners. Using sexual behavior data from rural Malawi and urban Kenya, we investigate the relationship between partnership concurrency and coital frequency, and find partial support for the coital dilution hypothesis. We conclude the paper with a discussion of our findings in light of the current literature on concurrency.

Determinants of generalized herpes simplex virus-2 epidemics: the role of sexual partner concurrency

Little is known as to why some populations develop generalized herpes simplex virus 2 (HSV-2) epidemics. Sexual network-level factors, such as the proportion of partnerships that run concurrently, are plausible explanations. In this ecological analysis, we used Spearman's correlation coefficients to assess if there is an association between population prevalence of point-concurrency and HSV-2 in a number of national and subnational populations. We found that there is an association between prevalence of point-concurrency and female HSV-2 prevalence between different countries (Spearman's rho = 0.715; P = 0.020), and within different races and ethnic groups within countries. In addition, there was a strong association between peak HIV and HSV-2 prevalence in 40-44-year-old women at an international level (Spearman's rho = 0.720; P = 0.0001). This could be indicative of populations with high HIV and HSV-2 prevalence rates having extensively connected sexual networks which puts them at increased risk of spread by both these sexually transmitted infections (STIs). No country with an HSV-2 prevalence of under 20% in their 20-24-year-old women had a generalized HIV epidemic. Thus, HSV-2 prevalence in adolescents may be a useful marker of how risky a local sexual network is for STI spread and may provide a useful early indicator of the success or failure of behavior change initiatives.

HIV prevalence by race co-varies closely with concurrency and number of sex partners in South Africa

BACKGROUND

HIV prevalence differs by more than an order of magnitude between South Africa's racial groups. Comparing the sexual behaviors and other risk factors for HIV transmission between the different races may shed light on the determinants of South Africa's generalized HIV epidemic.

METHODS

Five nationally representative and one city-representative population-based surveys of sexual behavior were used to assess the extent to which various risk factors co-varied with HIV prevalence by race in South Africa.

RESULTS

In 2004, the prevalence of HIV was 0.5%, 1%, 3.2% and 19.9% in 15-49 year old whites, Indians, coloureds and blacks respectively. The risk factors which co-varied with HIV prevalence by race in the six surveys were age of sexual debut (in five out of five surveys for men and three out of six surveys for women), age gap (zero surveys in men and three in women), mean number of sex partners in the previous year (five surveys in men and three in women) and concurrent partnerships (five surveys in men and one in women). Condom usage and circumcision were both more prevalent in the high HIV prevalence groups. The reported prevalence of concurrency was 6 to 17 times higher in the black as opposed to the white men in the five surveys.

CONCLUSIONS

The differences in sexual behavior in general, and the prevalence of concurrency and the number of sexual partners in particular, offer a plausible and parsimonious cause to explain a part of the differing prevalences of HIV between South Africa's racial groups.

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.

The effect of interview method on self-reported sexual behavior and perceptions of community norms in Botswana

Since self-reports of sensitive behaviors play an important role in HIV/AIDS research, the accuracy of these measures has often been examined. In this paper we (1) examine the effect of three survey interview methods on self-reported sexual behavior and perceptions of community sexual norms in Botswana, and (2) introduce an interview method to research on self-reported sexual behavior in sub-Saharan Africa. Comparing across these three survey methods (face-to-face, ballot box, and randomized response), we find that ballot box and randomized response surveys both provide higher reports of sensitive behaviors; the results for randomized response are particularly strong. Within these overall patterns, however, there is variation by question type; additionally the effect of interview method differs by sex. We also examine interviewer effects to gain insight into the effectiveness of these interview methods, and our results suggest that caution be used when interpreting the differences between survey methods.

Is concurrency driving HIV transmission in sub-Saharan African sexual networks? The significance of sexual partnership typology

Recently, there has been debate about the role of concurrent partnerships in driving the transmission of HIV, particularly in Southern Africa, where HIV prevalence is up to 25 % in many heterosexual populations and where evidence from sexual behavior surveys also suggests high levels of male concurrency. While mathematical modeling studies have shown that concurrency has the potential to enhance the speed at which HIV spreads in a population, empirical studies up to now have failed to provide conclusive evidence supportive of these effects. Here we discuss some reasons for the apparent discrepancy between theoretical and empirical studies. We propose that studying the impact of concurrency on HIV transmission should be differentiated by taking more insight from social and behavioral studies on sexual partnerships into account. We also suggest that a more rigorous definition is needed for when a factor is considered a driving force for HIV epidemic spread. We illustrate this with a modeling example.

Profile: the Karonga Health and Demographic Surveillance System

The Karonga Health and Demographic Surveillance System (Karonga HDSS) in northern Malawi currently has a population of more than 35 000 individuals under continuous demographic surveillance since completion of a baseline census (2002–2004). The surveillance system collects data on vital events and migration for individuals and for households. It also provides data on cause-specific mortality obtained by verbal autopsy for all age groups, and estimates rates of disease for specific presentations via linkage to clinical facility data. The Karonga HDSS provides a structure for surveys of socio-economic status, HIV sero-prevalence and incidence, sexual behaviour, fertility intentions and a sampling frame for other studies, as well as evaluating the impact of interventions, such as antiretroviral therapy and vaccination programmes. Uniquely, it relies on a network of village informants to report vital events and household moves, and furthermore is linked to an archive of biological samples and data from population surveys and other studies dating back three decades.