Partner Acquisition Research Articles

Modeling of US Human Papillomavirus (HPV) Seroprevalence by Age and Sexual Behavior Indicates an Increasing Trend of HPV Infection Following the Sexual Revolution.

The United States has experienced an increase in the incidence of human papillomavirus (HPV)-related cancers that are not screen-detectable. It has been hypothesized, but not directly demonstrated, that this is due to increasing HPV prevalence in the unvaccinated population. Female self-reported numbers of lifetime sex partners and HPV serology from the National Health and Nutrition Examination Survey (NHANES) were used to develop mathematical models of sexual partner acquisition and antibody dynamics. Modeled trends in sexual behaviors were compared to incidence data for cervical adenocarcinoma, oropharyngeal cancer, and anal cancer. The age-specific HPV seroprevalence data were best explained by a partner acquisition model that explicitly accounted for cohort-dependent changes in sexual behavior. Estimates of the mean time to loss of natural antibodies varied by model, ranging from 49 to 145 years. Inferred trends in sexual behavior over the past decades paralleled the increasing incidence of HPV-related cancers in the United States. The findings suggest that lower HPV seroprevalence in older US women primarily reflects cohort-specific differences in sexual behaviors, and is only marginally attributable to immune waning with age. Our results emphasize the importance of continuing surveillance of sexual behaviors, alongside vaccine status, to predict future disease burden.

Does antiretroviral therapy change partnership dynamics and HIV risk behaviours among HIV-infected adults.

Objective:We explore the impact of antiretroviral therapy (ART) on partnership acquisition and dissolution rates and changes in sexual behaviours among HIV-infected adults.Design:Using detailed longitudinal data from a prospective cohort of HIV-infected adults with CD4+ cell count below 200 cells/μl (ART-eligible) or CD4+ cell count above 500 cells/μl (pre-ART) conducted in rural KwaZulu-Natal, South Africa, from 2009 to 2012.Methods:Partnership acquisition and dissolution are explored through survival analysis methods, whereas generalized linear models were fitted for the sexual behaviour outcomes with interaction terms to allow the association with ART to vary over time. Throughout, the primary comparison of interest for each outcome is differences between the two ART groups.Results:ART is not associated with partner acquisition or relationship dissolution. During follow-up, the two ART groups do not differ in the odds of being sexually active nor the number of sex acts, whereas the odds of unprotected sex are significantly lower for partnerships of ART-eligible participants (adjusted odds ratio 0.26, 95% confidence interval 0.15, 0.43). Relationship-level characteristics including cohabitation status and wanting more children with that partner are associated with higher odds and increased frequency of sexual activity, and increased odds of unprotected sex, whereas living with partner, higher relationship quality and longer relationship duration are associated with lower risk of partnership dissolution.Conclusion:Being on ART was not associated with increased sexual risk behaviours, a reassuring finding given the WHO recommends ART initiation upon HIV diagnosis. The importance of relationship-level characteristics provides evidence that HIV care services should offer routine support for HIV disclosure and sexual risk reduction, and promotion of couples-testing and positive couple relationships.

Assortativity and Mixing by Sexual Behaviors and Sociodemographic Characteristics in Young Adult Heterosexual Dating Partnerships.

Assortative sexual mixing, the tendency for individuals to choose partners with similar characteristics to themselves, may be an important contributor to the unequal distribution of sexually transmitted infections in populations. We analyzed the tendency for assortative mixing on demographic and sexual behaviors characteristics in newly formed young adults dating partnerships. Women aged 18 to 24 years and their male sexual partners of no more than 6 months were recruited during 2005 to 2010 at universities in Montreal, Canada. New dating partners were also prospectively recruited during the 2-year follow-up. We used Spearman and Newman coefficients to examine correlations between partners' demographic characteristics and sexual behaviors, and multivariable logistic modeling to determine which characteristics were assortative. Participants in 502 recruited partnerships were assortative on age (Spearman P = 0.60), smoking behavior (P = 0.43), ethnicity (Newman coefficient=0.39), lifetime number of sexual partners (P = 0.36), sex partner acquisition rates (P = 0.22), gap length between partnerships (P = 0.20), and on whether they had concurrent partners (P = 0.33). Partners were assortative on number of lifetime partners, sexual partner acquisition rates, concurrency, and gap length between partnerships even after adjustment for demographic characteristics. Reported condom use was correlated between initial and subsequently recruited partners (P = 0.35). There was little correlation between the frequencies of vaginal/oral/digital/anal sex between subsequent partnerships. Dating partnerships were substantially assortative on various sexual behaviors as well as demographic characteristics. Though not a representative population sample, our recruitment of relatively new partnerships reduces survivor bias inherent to cross-sectional surveys where stable long-term partnerships are more likely to be sampled.

Does online dating lead to higher sexual risk behaviour? A cross-sectional study among MSM in Amsterdam, the Netherlands.

BackgroundMen having sex with men (MSM) frequently use the Internet to find sex partners. We examined the association between unprotected anal intercourse (UAI) with partners dated online and with partners dated offline (met elsewhere), and examined whether differences can be explained by self-perceived HIV status of the index and knowledge of partnership characteristics.MethodsMSM were recruited at the Sexually Transmitted Infections Clinic in Amsterdam, in 2008–2009. Participants completed a questionnaire concerning sexual behaviour. Only men reporting both online and offline casual sex partners were included. We assessed the association between online/offline partner dating and UAI, using random-effects logistic regression analysis.ResultsFive hundred seventy-seven men (351 HIV-negative, 153 HIV-positive, and 73 HIV-unaware) reported UAI in 26 % of 878 online, and 23 % of 903 offline casual partnerships. The crude OR of online dating for UAI was 1.36 (95 % CI 1.03–1.81). HIV-positive men were more likely to report UAI than HIV-negative men (49 % vs. 28 % of partnerships). Adjusted for demographic characteristics, online dating had no significant effect on UAI among HIV-negative and HIV status-unaware men, but HIV-positive men were more likely to have UAI with online partners (aOR = 1.65 [95 % CI 1.05–2.57]). After correction for partner and partnership characteristics the effect of online/offline dating on UAI among HIV-positive MSM was reduced and no longer significant.ConclusionsOnline dating was not significantly associated with UAI among HIV-negative MSM. HIV-positive MSM were more likely to practise UAI with partners dated online; however, after correction for partner and partnership characteristics, online partnership acquisition was not associated with a significantly increased risk of UAI.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1637-5) contains supplementary material, which is available to authorized users.

Sexual behaviour of backpackers who visit Koh Tao and Koh Phangan, Thailand: a cross-sectional study

ObjectivesTo measure the proportion of backpackers engaging in unprotected sex while travelling in Thailand and to identify predictors of unsafe sexual behaviour.MethodsA cross-sectional study using an anonymous questionnaire was performed....

Development, calibration and performance of an HIV transmission model incorporating natural history and behavioral patterns: application in South Africa.

Understanding HIV transmission dynamics is critical to estimating the potential population-wide impact of HIV prevention and treatment interventions. We developed an individual-based simulation model of the heterosexual HIV epidemic in South Africa and linked it to the previously published Cost-Effectiveness of Preventing AIDS Complications (CEPAC) International Model, which simulates the natural history and treatment of HIV. In this new model, the CEPAC Dynamic Model (CDM), the probability of HIV transmission per sexual encounter between short-term, long-term and commercial sex worker partners depends upon the HIV RNA and disease stage of the infected partner, condom use, and the circumcision status of the uninfected male partner. We included behavioral, demographic and biological values in the CDM and calibrated to HIV prevalence in South Africa pre-antiretroviral therapy. Using a multi-step fitting procedure based on Bayesian melding methodology, we performed 264,225 simulations of the HIV epidemic in South Africa and identified 3,750 parameter sets that created an epidemic and had behavioral characteristics representative of a South African population pre-ART. Of these parameter sets, 564 contributed 90% of the likelihood weight to the fit, and closely reproduced the UNAIDS HIV prevalence curve in South Africa from 1990–2002. The calibration was sensitive to changes in the rate of formation of short-duration partnerships and to the partnership acquisition rate among high-risk individuals, both of which impacted concurrency. Runs that closely fit to historical HIV prevalence reflect diverse ranges for individual parameter values and predict a wide range of possible steady-state prevalence in the absence of interventions, illustrating the value of the calibration procedure and utility of the model for evaluating interventions. This model, which includes detailed behavioral patterns and HIV natural history, closely fits HIV prevalence estimates.

Differential processes of ‘Internet’ versus ‘real life’ sexual filtering and contact among men who have sex with men

We studied the behaviors and sexual contacts in 1,000 Men who have Sex with Men (MSM), and behaviors for main and casual partners, and between Internet and In Real Life (IRL) sexual contacts for non-main partners. Data establish different patterns of MSM courtships and a pattern of partner acquisition. Data indicate the process of filtering, courtship, and / or negotiating for sex (including positioning) is different for Internet-acquired and IRL-acquired partners. There are more steps in the Internet process compared to the IRL processes prior to face-to-face contact, as well as negotiations of risk reduction. Higher levels of risk behavior and specifically anal sex and rimming suggest that the Internet allows for pre-Face-To-Face negotiation of sexual scripts.

Estimation of the HIV Basic Reproduction Number in Rural South West Uganda: 1991–2008

BackgroundThe basic reproduction number, , is one of the many measures of the epidemic potential of an infection in a population. We estimate HIV over 18 years in a rural population in Uganda, examine method-specific differences in estimated , and estimate behavioural changes that would reduce below one.MethodsData on HIV natural history and infectiousness were collated from literature. Data on new sexual partner count were available from a rural clinical cohort in Uganda over 1991–2008. was estimated using six methods. Behavioural changes required to reduce below one were calculated.ResultsReported number of new partners per year was 0 to 16 (women) and 0 to 80 (men). When proportionate sexual mixing was assumed, the different methods yielded comparable estimates. Assuming totally assortative mixing led to increased estimates in the high sexual activity class while all estimates in the low-activity class were below one. Using the “effective” partner change rate introduced by Anderson and colleagues resulted in estimates all above one except in the lowest sexual activity class. could be reduced below one if: (a) medium risk individuals reduce their partner acquisition rate by 70% and higher risk individuals reduce their partner acquisition rate by 93%, or (b) higher risk individuals reduce the partner acquisition rate by 95%.ConclusionsThe estimated depended strongly on the method used. Ignoring variation in sexual activity leads to an underestimation of . Relying on behaviour change alone to eradicate HIV may require unrealistically large reductions in risk behaviour, even though for a small proportion of the population. To control HIV, complementary prevention strategies such as male circumcision and HIV treatment services need rapid scale up.

A Tighter Embrace: When Does an Alliance Lead to Partner Acquisition?

We examine the conditions under which an alliance partnership is likely to be followed by one partner acquiring the other parent, rather than by a next alliance between the same firms. Although res...

P3.064 Patterns of Sexual Partner Accrual Among Adolescent Women

Background Younger age and number of sexual partners are consistently identified STI risk factors, but the relative contributions of chronological age and total interval since first coital partner to accrual of partners has not been established in prospective studies. Methods Participants (N = 341; 14–17 years of age at enrollment; 90% African American) were English-speaking adolescent women from lower- and middle-income families residing in areas with high rates of pregnancy and STI. We collected quarterly sexual behaviour data for an average of 3.56 years (range 0.23–8.92 years). Median number of lifetime partners increased from 2 at enrollment to 6 at the last visit. Generalized Additive Mixed Models were used to estimate the cumulative number of partners as a function of time covariates. The cohort effect (enrollment age), the longitudinal effect (follow-up period) and their interaction were considered as predictors. Annual rate of the partner acquisition was estimated by the first derivative of the cumulative number of partners with respect to the “follow-up period”. Results Partner accrual was 2 or more partners per annum within the first 2 years of follow-up, but slowed down to about 1 partner per annum during the years 2 to 5 since enrollment. Rates of partner accrual were similar for all age groups at enrollment and declined at similar rates. Correlation between “enrollment age” and “age at first sex” was 0.26, possibly an indicator of STI and contraceptive care-seeking associated with sexual activity. Conclusions Cross-sectional studies of STI risk among adolescents may confound age-related cohort effects with variation in interval since first sexual intercourse. Our analysis shows that higher rates of partner accrual decrease within two years regardless of the age of first coitus. This suggests that STI prevention based on delay of coitus among adolescent women should be supplemented with efforts to reduce rates of partner accrual.

Heterosexual partner acquisition rates in the Australian population

The rate of partner acquisition in a population is an important parameter when constructing epidemiological models of sexually transmissible infections. We have analysed the results of a survey of the sexual behaviour of the Australian population to estimate how many people have acquired no new partner, one, two or at least three new partners in the past year, and hence estimated heterosexual partner acquisition rates for the population by gender and age band. Partner acquisition rates are ~0.5 new partners per year for 16- to 19-year-olds, peak at ~0.7 in the 20- to 24-year-old age band, and then decline steadily with age to ~0.2 per year. In all age bands, there are more male respondents reporting three or more new partners in the last year than what is consistent with the rest of the data, which could be interpreted as evidence of an additional population stratum characterised by higher partner acquisition rates.

Size Matters: Concurrency and the Epidemic Potential of HIV in Small Networks

BackgroundGeneralized heterosexual epidemics are responsible for the largest share of the global burden of HIV. These occur in populations that do not have high rates of partner acquisition, and research suggests that a pattern of fewer, but concurrent, partnerships may be the mechanism that provides the connectivity necessary for sustained transmission. We examine how network size affects the impact of concurrency on network connectivity.Methodology/Principal FindingsWe use a stochastic network model to generate a sample of networks, varying the size of the network and the level of concurrency, and compare the largest components for each scenario to the asymptotic expected values. While the threshold for the growth of a giant component does not change, the transition is more gradual in the smaller networks. As a result, low levels of concurrency generate more connectivity in small networks.Conclusions/SignificanceGeneralized HIV epidemics are by definition those that spread to a larger fraction of the population, but the mechanism may rely in part on the dynamics of transmission in a set of linked small networks. Examples include rural populations in sub-Saharan Africa and segregated minority populations in the US, where the effective size of the sexual network may well be in the hundreds, rather than thousands. Connectivity emerges at lower levels of concurrency in smaller networks, but these networks can still be disconnected with small changes in behavior. Concurrency remains a strategic target for HIV combination prevention programs in this context.

A Comparison of Sexual Behavior Patterns Among Men Who Have Sex With Men and Heterosexual Men and Women

Men who have sex with men (MSM) have higher rates of HIV and other sexually transmitted infections than women and heterosexual men. This elevated risk persists across age groups and reflects biological and behavioral factors; yet, there have been few direct comparisons of sexual behavior patterns between these populations. We compared sexual behavior patterns of MSM and male and female heterosexuals aged 18-39 using 4 population-based random digit dialing surveys. A 1996-1998 survey in 4 US cities and 2 Seattle surveys (2003 and 2006) provided estimates for MSM; a 2003-2004 Seattle survey provided data about heterosexual men and women. Sexual debut occurred earlier among MSM than heterosexuals. MSM reported longer cumulative lifetime periods of new partner acquisition than heterosexuals and a more gradual decline in new partnership formation with age. Among MSM, 86% of 18- to 24-year-olds and 72% of 35- to 39-year-olds formed a new partnership during the previous year, compared with 56% of heterosexual men and 34% of women at 18-24 years, and 21% and 10%, respectively, at 35-39 years. MSM were also more likely to choose partners >5 years older and were 2-3 times as likely as heterosexuals to report recent concurrent partnerships. MSM reported more consistent condom use during anal sex than heterosexuals reported during vaginal sex. MSM have longer periods of partnership acquisition, a higher prevalence of partnership concurrency, and more age disassortative mixing than heterosexuals. These factors likely help to explain higher HIV/sexually transmitted infections rates among MSM, despite higher levels of condom use.

Sexually Transmitted Infections, Sexual Risk Behavior, and Intimate Partner Violence Among African American Adolescent Females With a Male Sex Partner Recently Released from Incarceration

Social networks directly and indirectly influence sexually transmitted infections (STIs) risk. The objective was to explore associations between sex with a male recently released from incarceration and sexual risk and intimate partner violence (IPV) among African American adolescent females. Sociodemographic, psychosocial, and sexual behavior data were collected at baseline, 6, and 12 months from African American females, aged 15-21 years, participating in an HIV/STI prevention trial. Among 653 participants with ≥1 follow-up assessments, generalized estimating equations tested associations during follow-up between having a recently released partner and STI acquisition, sexual risk behaviors, and IPV, adjusting for age, treatment assignment, and corresponding baseline measure. Eighty-three (13.6%) participants had a recently released partner at 6 months and 56 (9.3%) at 12 months. Participants with a recently released partner were more likely to have the following: vaginal (adjusted odds ratio [AOR]: 5.48), anal (AOR: 2.43), and oral (AOR: 1.51) sex, a casual partner (AOR: 1.66), sex while high/drunk (AOR: 1.57) or with a high/drunk partner (AOR: 2.27); use condoms inconsistently (AOR: .58); acquire Chlamydia (AOR: 1.80), and experience emotional (AOR: 4.09), physical (AOR: 2.59), or sexual abuse (AOR: 4.10) by a boyfriend. They had a greater number of sex partners, lower partner communication and refusal self-efficacy, were high/drunk during sex more frequently, and used condoms during oral sex less frequently. A recently released sex partner is associated with sexual risk and IPV among African American adolescent females. Prevention programs should inform adolescents about potential risks associated with recently released partners as well as provide adolescents with skills to establish and maintain healthy sexual relationships.

Will Changes in Gay Men's Sexual Behavior Reduce Syphilis Rates?

Reducing rates of partner change and increasing condom usage among gay men are obvious targets for potentially reducing syphilis transmission among gay men. We developed an agent-based stochastic model to examine syphilis transmission among a population of gay men, representative of gay men in Australia. This model was used to explore the potential impact of changes in sexual behavior over 1 month, 3 month, and indefinite time frames on syphilis epidemics. Simulations of interventions showed that short-term reductions in rates of partner change and increased condom use would have negligible impact on the long-term trends of syphilis epidemics. If no interventions are introduced, then the model forecasts that the syphilis prevalence in the population could continue to rise, with an increase of 80% in the number of men infected with syphilis during the next decade. However, if changes in sexual behavior are maintained in the long-term, then syphilis epidemics can be mitigated. If condom use is sustained at 80% in partnerships that are HIV discordant or of unknown status, then the prevalence of syphilis is estimated to decrease by 9% over 10 years. Similarly, if partner acquisition rates decrease by 25%, then there will be a 22% reduction in syphilis prevalence. Interventions promoting partner reduction or increased condom use would be ineffective in the short-term, and would have limited prospects for success in the long-term unless very large changes in behavior are sustained. Complementary social research indicates that such long-term changes in behavior are unlikely to be adopted, and therefore other intervention strategies need to be developed to reduce syphilis among gay men.

Would Gay Men Change Their Sexual Behavior to Reduce Syphilis Rates?

The community at which public health strategies for reducing syphilis epidemics are potentially targeted may have different considerations with regards to their sexual and health priorities. We aimed to elicit information on the acceptability of behavior change interventions among gay men for reducing syphilis transmission. We conducted an online survey (n = 2306 participants) and focus groups to determine whether further sexual behavior change to reduce syphilis is likely to be acceptable to gay men in Australia. One quarter of survey respondents (26%) indicated that they would be highly likely to reduce partner acquisition rates in order to reduce their chances of syphilis infection. However, among the 475 (21%) men who reported greater than 10 partners in the previous 6 months, only 11% indicated being "highly likely" to reduce partner numbers to avoid syphilis. Among 606 (26%) survey respondents who reported not always using condoms in the previous 6 months, 34% indicated being highly likely to always use condoms with casual partners to avoid syphilis. In the focus groups, men indicated little commitment to sexual behavior change but some willingness to consider short-term changes to reduce community syphilis levels. Interventions promoting partner reduction or increased condom use are unlikely to be adopted on a long-term basis by men at greatest risk. Behavioral interventions alone are unlikely to materially contribute to syphilis prevention among gay men.

P1-S2.18 Syphilis prevalence and related risk factors among female workers at social venues in Liuzhou, China

BackgroundIn the context of rapid urbanisation and economic growth in China, places where social mixing intersects with commercial activities could play an important role in the formation of new partnerships...

Sexual and HIV risk behaviour in Central and Eastern European migrants in London

BackgroundAccession of 10 Central and Eastern European (CEE) countries to the EU resulted in the largest migratory influx in peacetime British history. No information exists on the sexual behaviour of...

Modelling the HIV/AIDS epidemic trends in South Africa: Insights from a simple mathematical model

The HIV/AIDS epidemic is a serious public health challenge in South Africa. In this paper, a simple deterministic HIV/AIDS model incorporating condom use, sexual partner acquisition, behavior change and treatment as HIV/AIDS control strategies is formulated using a system of ordinary differential equations with the object of applying it to the current South African situation. Firstly, a theoretical analysis of the model is presented. The analysis of the model shows that the disease free equilibrium point is globally asymptotically stable for the epidemic threshold R (the model reproduction number) less than unit and unstable when this threshold is greater than unit. A unique endemic equilibrium, whose local stability near the threshold R , is determined using the center manifold theory, is shown to be locally asymptotically stable for R > 1 . Global stability of the endemic equilibrium is shown for a special case whenever R > 1 . Secondly, the model is fitted to data from UNAIDS/WHO on HIV/AIDS in South Africa. Based on the fit to the prevalence data, projections are made beyond 2007 on the course of the epidemic for various levels of interventions. The results compare very well with other research outcomes on the HIV/AIDS epidemic in South Africa. Projections are made to track the changes in the number of individuals who will be under treatment, an important group as far as public health planning is concerned. The epidemiological implications of such projections on public health planning and management are discussed.

Variation in social organization influences the opportunity for sexual selection in a social lizard

Social monogamy has traditionally been suggested to be maintained because of weak sexual selection on male partner acquisition. However, the ubiquitous incidence of extra-pair paternity suggests that sexual selection can be strong in monogamous systems, although studies partitioning variance in male reproductive success have come to mixed conclusions. Here, we use detailed field data to examine variance in male reproductive success and its implications for the maintenance of sociality in a population of the socially monogamous lizard Egernia whitii. We show that both within-pair and, to a lesser extent, extra-pair partner acquisition contribute to the variance in male reproductive success, resulting in considerable opportunity for sexual selection. Despite this, levels of multiple mating are lower in Egernia compared to other reptiles, suggesting that male partner acquisition is constrained. We suggest that this constraint may be a result of strong territoriality combined with sexual conflict over multiple mating generated by costs of extra-pair paternity to females as a result of facultative male care. This has the potential to limit sexual selection by reducing variance in male reproductive success and therefore contribute to the maintenance of complex social organization.