Rates Of Partner Change Research Articles

Resistance-minimising strategies for introducing a novel antibiotic for gonorrhoea treatment: a mathematical modelling study

Gonorrhoea is a highly prevalent sexually transmitted infection and an urgent public health concern because of increasing antibiotic resistance in Neisseria gonorrhoeae. Only ceftriaxone remains as the recommended treatment in the USA. With the prospect of new anti-gonococcal antibiotics being approved, we aimed to evaluate how to deploy a new drug to maximise its clinically useful lifespan. We used a compartmental model of gonorrhoea transmission in a US population of men who have sex with men (MSM) to compare strategies for introducing a new antibiotic for gonorrhoea treatment. The MSM population was stratified into three sexual activity groups (low, intermediate, and high) characterised by annual rates of partner change. The four introduction strategies tested were: (1) random 50-50 allocation, where each treatment-seeking infected individual had a 50% probability of receiving either drug A (current drug; a ceftriaxone-like antibiotic) or drug B (a new antibiotic), effective at time 0; (2) combination therapy of both the current drug and the new antibiotic; (3) reserve strategy, by which the new antibiotic was held in reserve until the current therapy reached a 5% threshold prevalence of resistance; and (4) gradual switch, or the gradual introduction of the new drug until random 50-50 allocation was reached. The primary outcome of interest was the time until 5% prevalence of resistance to each of the drugs (the new drug and the current ceftriaxone-like antibiotic); sensitivity of the primary outcome to the properties of the new antibiotic, specifically the probability of resistance emergence after treatment and the fitness costs of resistance, was explored. Secondary outcomes included the time to a 1% resistance threshold for each drug, as well as population-level prevalence, mean and range annual incidence, and the cumulative number of incident gonococcal infections. Under baseline model conditions, a 5% prevalence of resistance to each of drugs A and B was reached within 13·9 years with the reserve strategy, 18·2 years with the gradual switch strategy, 19·2 years with the random 50-50 allocation strategy, and 19·9 years with the combination therapy strategy. The reserve strategy was consistently inferior for mitigating antibiotic resistance under the parameter space explored and was increasingly outperformed by the other strategies as the probability of de novo resistance emergence decreased and as the fitness costs associated with resistance increased. Combination therapy tended to prolong the development of antibiotic resistance and minimise the number of annual gonococcal infections (under baseline model conditions, mean number of incident infections per year 178 641 [range 177 998-181 731] with combination therapy, 180 084 [178 011-184 405] with the reserve strategy). Our study argues for rapid introduction of new anti-gonococcal antibiotics, recognising that the feasibility of each strategy must incorporate cost, safety, and other practical concerns. The analyses should be revisited once robust estimates of key parameters-ie, the likelihood of emergence of resistance and fitness costs of resistance for the new antibiotic-are available. US Centers for Disease Control and Prevention, National Institute of Allergy and Infectious Diseases.

Accessible health care is critical to the effective control of sexually transmitted infections.

Bacterial sexually transmitted infections (STIs) are rising relentlessly in virtually every country and among most risk groups. These infections have substantial individual and community consequences and costs. This review summarises the evidence for the effectiveness of different strategies to control STIs and assumes countries have sufficient financial resources to provide accessible health care. Reducing the probability of transmission essentially involves increasing condom use, which is problematic given that condom use is currently falling in most risk groups. Interventions to increase condom use are expensive and hard to sustain. Only a limited number of studies have shown it is possible to reduce the rate of partner change and sustained changes are difficult. In contrast, the provision of accessible health care has a powerful effect on the incidence rate of STIs, with dramatic falls in STIs in virtually all countries following the discovery of antibiotics. More recent studies support the powerful role of accessible health care as a strategy for putting substantial downward pressure on STI rates. Accessible health care has a powerful effect on the incidence of STIs. The professionals who are responsible for funding these services need to appreciate that they are ultimately responsible for the rates of STIs in their communities. In contrast, personal behaviour plays a less powerful role in determining the incidence of STIs and is hard to change and sustain at a population level. The public needs to appreciate that it is the governments they elect and not individuals who are responsible for the rates of STIs in their communities.

Abstract PO-275: Assessing human papillomavirus vaccination-related knowledge, attitudes, and behaviors among young men who have sex with men

Abstract Human papillomavirus (HPV) is one of the most common sexually transmitted infections in the United States. HPV is acknowledged as one of the causes of anal cancer, with a 20-fold increased risk in men who have sex with men (MSM), when compared to age-matched heterosexual men. MSM are at potential high risk of contracting HPV, due to observed prevalence of risk factors such as a high number of sexual partners, rate of partner change, compromised immune system, and age. Vaccinations classified as HPV4 and HPV9 protect the aforementioned high-risk serotypes. Among MSM studies, few have focused on the needs, perceptions, knowledge, and intentions of young-MSM (Y-MSM) aged 18 to 27 years old pertaining to HPV diagnosis, associated anal cancer risks, and HPV vaccination intentions. To address this significant gap in the literature, we designed a pilot study to assess the knowledge, attitudes, and behaviors related to HPV vaccine and explore the contextual facilitators and barriers to HPV vaccination among Y-MSM, a vulnerable and medically underserved population in the greater Philadelphia metropolitan area. First, we conducted an online survey assessing vaccination intentions and background knowledge among 400 young-MSM living in the greater Philadelphia metropolitan area. Second, we examine the geospatial associations between the accessibility of HPV screening services, HPV diagnosis, and knowledge of anal cancer risks among 100 high-risk black and Hispanic MSM. The preliminary data will inform proactive and responsive methods to identify the needs of young- MSM pertaining to HPV vaccination intent, the prevalence of HPV within the population, and associated anal cancer risks to reduce disparities among at-risk Y- MSM. We will present results from preliminary data analysis and discuss the process of study design and implementation. We will also discuss implications for future research and public health interventions in HPV vaccine uptake among Y-MSM and other disparity populations. Citation Format: Tyrell Mann-Barnes, Aisha Bhimla, Timmy Lin, Adebola Florish Duro-Aina, Grace Ma. Assessing human papillomavirus vaccination-related knowledge, attitudes, and behaviors among young men who have sex with men [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-275.

Toward a Set of Criteria to Decide Which STIs to Screen for in PrEP Cohorts.

Contemporary HIV preexposure prophylaxis (PrEP) cohorts are characterized by high rates of partner change and as a result have high and fairly stable prevalences of N. gonorrhoeae and C. trachomatis. The available evidence suggests that intensive 3-monthly screening in this setting does not have a large effect on the prevalence of these infections but results in high antimicrobial exposures. Gonorrhea/chlamydia screening may thus be doing more harm than good. Compelling arguments can, however, be made to screen for HIV, hepatitis C, and syphilis in PrEP cohorts. In this perspective piece, we explore the logical basis for deciding which STIs to screen for in PrEP cohorts. We propose that a Delphi consensus methodology is used to derive, assess, and apply a broadly accepted set of criteria to evaluate which STIs to screen for in these cohorts. Finally, to illustrate the utility of the process, we derive and apply our own list of criteria as to which STIs to screen for. This process leads to a controversial conclusion, namely that stopping gonorrhea/chlamydia screening in a controlled and phased manner may offer net health benefits to PrEP cohorts.

Are associations between HIV and human papillomavirus transmission due to behavioural confounding or biological effects?

ObjectivesCohort studies have shown significant increased risk of HIV acquisition following human papillomavirus (HPV) detection and increased risk of new HPV detection in individuals with HIV infection, after adjusting for...

P212 The clap trap: the effectiveness of partner notification for gonorrhoea in MSM in an lgbt community sexual health clinic

IntroductionHigh rates of partner change, multiple casual partners, and complex sexual networks are thought to contribute to outbreaks of Neisseria gonorrhoea (GC) in men who have sex with men (MSM), who account for 42% of diagnoses in the UK. Prompt, appropriate treatment and effective partner notification are key to reducing transmission. We audited partner notification for GC in MSM attending an LGBT community sexual health clinic.MethodsA retrospective audit over 12 months (2015–16). A total of 33 episodes of GC were diagnosed in 31 patients. Data was recorded on a spreadsheet for analysis.Results25(76%) were asymptomatic. 29(88%) underwent triple site testing and 4(12%) dual site. Gonorrhoea was detected in the pharynx in 23(70%), urethra in 7(21%), and rectum in 14(42%). 7(21%) had dual and 2(6%) triple site infection. 29/33(88)% were informed of the diagnosis within 10 days (target 95%). 28/33(85%) were treated within 2 weeks. 6 attended as contacts of GC and were treated on the day they attended. A total of 109 contacts were given. 50(46%) were untraceable. Of the traceable contacts, 31/59(53%) were confirmed as treated, 23 at the same clinic. A total of 0.9 contacts were treated per index case (target 0.6).DiscussionThe high frequency of unknown casual partners in MSM with GC means there is often inadequate information to trace partners. Nevertheless, this audit has shown good outcomes for partner notification in a community LGBT sexual health clinic. This should contribute to reducing onward transmission in a high risk MSM population.

Human papillomavirus vaccination in men who have sex with men - what will be required by 2020 for the same dramatic changes seen in heterosexuals.

This paper addresses the issue of whether men who have sex with men (MSM) will share the spectacular reductions in human papillomavirus (HPV) infection and its associated neoplasia that we are currently witnessing in heterosexuals. The reproductive rate for HPV infection in heterosexuals is not well established, but 70% vaccination coverage in women has resulted in a fall of more than 90% in genital warts and HPV types 16/18 in young women and 80% fall in young men indicating that the critical vaccination threshold has been exceeded for this group. Published data on the three elements of the reproductive rate for HPV infection (i.e. transmission probability per sexual partnership, rate of partner change and duration of infectiousness) suggest they are higher in MSM than heterosexuals. This indicates that the reproductive rate for HPV will be higher in MSM and hence the critical vaccination threshold will also be higher. But while vaccinating 70% of girls protect 70% of sexual partnerships in heterosexuals, vaccinating 70% of boys protect more than 70% of partnerships in MSM. Only 9% (30% by 30%) of sexual partnerships in MSM are not protected with 70% coverage. Therefore vaccinating 70% of boys will protect 91% of sexual partnerships in MSM. However the efficacy of the HPV vaccine is much lower when sexually active MSM are vaccinated rather than boys. We argue that if MSM are to have the same benefit from the HPV vaccine that heterosexuals had, boys and not adult MSM will need to be vaccinated.

Impact of Heterogeneity in Sexual Behavior on Effectiveness in Reducing HIV Transmission with Test-and-Treat Strategy.

The WHO’s early-release guideline for antiretroviral treatment (ART) of HIV infection based on a recent trial conducted in 34 countries recommends starting treatment immediately upon an HIV diagnosis. Therefore, the test-and-treat strategy may become more widely used in an effort to scale up HIV treatment and curb further transmission. Here we examine behavioural determinants of HIV transmission and how heterogeneity in sexual behaviour influences the outcomes of this strategy. Using a deterministic model, we perform a systematic investigation into the effects of various mixing patterns in a population of men who have sex with men (MSM), stratified by partner change rates, on the elimination threshold and endemic HIV prevalence. We find that both the level of overdispersion in the distribution of the number of sexual partners and mixing between population subgroups have a large influence on endemic prevalence before introduction of ART and on possible long term effectiveness of ART. Increasing heterogeneity in risk behavior may lead to lower endemic prevalence levels, but requires higher coverage levels of ART for elimination. Elimination is only feasible for populations with a rather low degree of assortativeness of mixing and requires treatment coverage of almost 80% if rates of testing and treatment uptake by all population subgroups are equal. In this case, for fully assortative mixing and 80% coverage endemic prevalence is reduced by 57%. In the presence of heterogeneity in ART uptake, elimination is easier to achieve when the subpopulation with highest risk behavior is tested and treated more often than the rest of the population, and vice versa when it is less. The developed framework can be used to extract information on behavioral heterogeneity from existing data which is otherwise hard to determine from population surveys.

Feasible, Efficient and Necessary, without Exception - Working with Sex Workers Interrupts HIV/STI Transmission and Brings Treatment to Many in Need.

Background and OverviewHigh rates of partner change in sex work—whether in professional, ‘transactional’ or other context—disproportionately drive transmission of HIV and other sexually transmitted infections. Several countries in Asia have demonstrated that reducing transmission in sex work can reverse established epidemics among sex workers, their clients and the general population. Experience and emerging research from Africa reaffirms unprotected sex work to be a key driver of sexual transmission in different contexts and regardless of stage or classification of HIV epidemic. This validation of the epidemiology behind sexual transmission carries an urgent imperative to realign prevention resources and scale up effective targeted interventions in sex work settings, and, given declining HIV resources, to do so efficiently. Eighteen articles in this issue highlight the importance and feasibility of such interventions under four themes: 1) epidemiology, data needs and modelling of sex work in generalised epidemics; 2) implementation science addressing practical aspects of intervention scale-up; 3) community mobilisation and 4) the treatment cascade for sex workers living with HIV.ConclusionDecades of empirical evidence, extended by analyses in this collection, argue that protecting sex work is, without exception, feasible and necessary for controlling HIV/STI epidemics. In addition, the disproportionate burden of HIV borne by sex workers calls for facilitated access to ART, care and support. The imperative for Africa is rapid scale-up of targeted prevention and treatment, facilitated by policies and action to improve conditions where sex work takes place. The opportunity is a wealth of accumulated experience working with sex workers in diverse settings, which can be tapped to make up for lost time. Elsewhere, even in countries with strong interventions and services for sex workers, an emerging challenge is to find ways to sustain them in the face of declining global resources.

Etiological spectrum of cervicovaginal discharge among professional sex workers versus nonprofessionals

Abstract Context Vaginal discharge is a major problem for women, causing discomfort and anxiety, thus affecting the quality of their life. Sexually transmitted infections (STIs) are occurring in higher percentage in commercial sex workers, since they tend to have high rates of partner change and unprotected sex. Aims This study aims to find out the prevalence of various etiological agents of cervicovaginal discharge, identify coinfections, and determine antimicrobial susceptibility pattern of the isolates. Settings and design Cross sectional comparative study. Methods and materials High risk and low risk females, 50 each were included and high vaginal, cervical swabs, and blood samples were collected from each patient. Microscopy, culture, serology, and antimicrobial susceptibility tests were done. Statistical analysis Statistical analysis was done using Chi-square test (IBM-SPSS statistics version 22) and simple percentage calculation. Results Among the various etiologies of cervicovaginal discharge, candidiasis was the commonest followed by chlamydial cervicitis, bacterial vaginosis, aerobic vaginosis, trichomoniasis, and gonococcal cervicitis in order. Coinfections were found in more than a third of total positives. Conclusions Treatment failure in cervicovaginal discharge is mainly due to coinfections and resistant isolates, which emphasizes the importance of etiological diagnosis and susceptibility testing.

S14.2 Age, sexual experience and mucosal inflammation: what do we know?

HIV transmission rates are low on a per-coital level, but increased by various transmission co-factors. One implication of this is that the mucosal environment of female reproductive tract – in the case of male-to-female transmission – is generally capable of repelling the virus. Several lines of evidence have linked HIV transmission co-factors with altered mucosal immune parameters. Mucosal inflammation, defined by elevated cytokine concentrations in cervicovaginal secretions, was associated with increased rates of HIV acquisition in the CAPRISA 004 study. While the causes of these remain unclear, we have also shown that mucosal cytokines are associated with an altered mucosal proteome including impaired barrier function, and increased frequencies of HIV target cells in the mucosa. A further proteomic analysis of HIV cases and controls demonstrated that HIV outcome could be predicted with 97% accuracy on the basis of 10 key proteins. Proteins overrepresented in cases included those associated with inflammation, while barrier-associated proteins were overrepresented in controls. Application of this model to younger women, who in the sub-Saharan African epidemic represent the group with the highest incidence rates, will be important to understanding HIV risk. In particular, the role of sex work-related exposures including rates of condom use, partner change, vaginal practices, microbiome, and other infections in driving immune changes remains poorly described. A better understanding of HIV transmission at a mucosal level may reveal novel HIV prevention options.

P14.12 Nsw sexual health promotion

Background Sexual health promotion is central to the prevention of human immunodeficiency virus (HIV) and sexually transmissible infections (STIs) and to achieving the targets of the NSW HIV Strategy 2012–2015 and the forthcoming NSW STI Plan. In NSW sexual health promotion targeting young people is delivered by local health district HIV and Related Programs (HARP) Units, non-government organisations and state-wide services. In the past state level leadership and coordination of sexual health promotion has been limited, consequently many services have been working in isolation and delivering small scale programs with limited evaluation. Methods During 2014 the NSW Ministry of Health (MOH) undertook a review with the aim of strengthening the State’s response to sexual health promotion. The review involved a staged approach including: An evidence check of evidence-based practice in HIV, STI and viral hepatitis health promotion and Aboriginal community engagement; A review of data; Consultation with key stakeholders to map existing infrastructure and resources, current sexual health promotion work and to identify barriers and enablers for the services. Results The evidence check found patchy evidence to guide health promotion efforts. The review of current sexual health promotion across NSW identified a gap in state-wide prevention activity targeting young people aged 16 to 29 was. Young people have high notification rates for chlamydia, high rates of partner change and barriers to accessing health services. Conclusions In response to these findings MOH developed the NSW Sexual Health Promotion Framework for the delivery of an integrated population-based prevention program that aims to increase consistent condom use and health seeking behaviours (STI/HIV testing and treatment) among young people. The Framework also aims to reduce duplication, strengthen partnerships across the sector and enable robust evaluation and monitoring of program outcomes. Implementation of the Framework has commenced. Disclosure of interest statement Nil.

P04.20 Incident sexually transmitted infection and post-infection partner change

Introduction Sex partner change is necessary to maintain STI within a population. However, most people change partners relatively infrequently, and the timing of partner changes relative to incident STI is poorly understood. Methods 272 participants without STI at enrollment (18–29 years of age; 126 (46%) men/146 (54%) women) from a high STI population completed a 12-week study of daily reports of partner-specific sexual behaviours. None reported commercial sex work. Weekly self-obtained vaginal or urine samples were tested (and treated, if positive) at the end of 12-weeks for C trachomatis (CT), N gonorrhoeae (GC), and T vaginalis (TV) using commercially available NAAT. Survival analysis techniques were used to describe time to first partner change following first NAAT+. Results 15, 12, and 23 participants acquired an incident CT+, GC+, or TV+ NAAT. Partner change after the first NAAT+ test was seen for 7 (47%), 6 (50%), and 3 (13%) participants with CT+, GC+, or TV+ NAAT, respectively. Median time to partner change after first NAAT+ 7.6 and 4.6 weeks following CT+ or GC+, respectively. Among 231 participants with no incident NAAT+ during 12 weeks of followup, 89 (39%) changed partners. Conclusion Persons with incident STI have higher rates of partner change than those without incident STI. Rapid partner change is common following a new CT or GC infection, but less common for TV. Interventions focused on short-term partner change could be especially effective approaches to CT and GC control efforts. Disclosure of interest statement This research was funded by the National Institute of Child Health and Human Development. The authors have no relevant conflict of interest to disclose.

P09.13 Impact and cost-effectiveness of point-of-care testing for chlamydia: accounting for geographic variation in infection burden and testing rates, health service configuration, and implementation strategy

Introduction Point-of-care tests (PoCTs) for Chlamydia trachomatis potentially improve control by reducing transmission through reduced treatment delay, reduced loss to follow up, and greater convenience for patients leading to increased testing. However, with ~3–5 fold variation in rates of Chlamydia testing and diagnosis across geographic settings in England, in assessing cost-effectiveness the epidemiological context needs to be considered. Methods We developed a transmission-dynamic model to capture geographic variation in rates of testing and diagnosis using current technology to allow assessment of the impact of implementing PoCTs in different clinical services in different localities. The model incorporates heterogeneity in sexual partner change rates and is stratified by age and sex. It uses behavioural and prevalence data from the Natsal national survey, and Public Health England surveillance data on testing and diagnosis rates. Uncertainty in natural history and behavioural parameters is captured by Monte Carlo methods. Health service reconfiguration using PoCT is considered, including rates of PoCT introduction and reduction in presumptive treatment. Results The model captures observed geographic variation in rates of testing and diagnosis in females and males, which affects the impact and cost-effectiveness of PoCT introduction. In general, whilst PoCTs may reduce incidence by increasing diagnosis and treatment, if sensitivity is lower than conventional testing then there is potentially increased transmission from false-negative patients. The net effect depends upon characteristics of the particular PoCT. Conclusion PoCT sensitivity and specificity are key determinants of whether replacing conventional testing is likely to reduce or increase the incidence of infection. Importantly, if the convenience of PoCT increases testing rates then diagnoses might initially increase even though incidence falls; interpretation of surveillance data needs to account for this. This work is the foundation of a user-friendly web-based tool assessing the (cost-) effectiveness of introducing PoCTs in different local settings. Disclosure of interest statement CED, ESS, NG, EHE, RHJ, YC, CML, and PJW thank Innovate UK for funding. PJW thanks the UK Medical Research Council for Centre funding (grant MR/K010174/1), and also thanks the UK National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Modelling Methodology at Imperial College London in partnership with Public Health England (PHE) for funding (grant HPRU-2012–10080). The funding sources had no involvement in the study design or conduct; the collection, analysis and interpretation of data; the preparation, review or approval of the manuscript; or the decision to submit the manuscript for publication. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health, or Public Health England. CED was employed for part of the project by the National Chlamydia Screening Programme. The other authors declare no competing interests.

Mate Familiarity Affects Pairing Behaviour in a Long‐Term Monogamous Lizard: Evidence from Detailed Bio‐Logging and a 31‐Year Field Study

AbstractLong‐term monogamy is most prevalent in birds but is also found in lizards. We combined a 31‐year field study of the long‐lived, monogamous Australian sleepy lizard, Tiliqua rugosa, with continuous behavioural observations through GPS data logging, in 1 yr, to investigate the duration of pair bonds, rates of partner change and whether either the reproductive performance hypothesis or the mate familiarity hypothesis could explain this remarkable long‐term monogamy. The reproductive performance hypothesis predicts higher reproductive success in more experienced parents, whereas the mate familiarity hypothesis suggests that effects of partner familiarity select for partner retention and long‐term monogamy. Rates of partner change were below 34% over a 5‐yr period and most sleepy lizards formed long‐term pair bonds: 31 partnerships lasted for more than 15 yr, 110 for more than 10 yr, and the recorded maximum was 27 yr (ongoing). In the year when we conducted detailed observations, familiar pairs mated significantly earlier than unfamiliar pairs. Previous pairing experience (total number of years paired with previous partners) had no significant effect. Early mating often equates to higher reproductive success, and we infer that is the case in sleepy lizards. Early mating of familiar pairs was not due to better body condition. We propose two suggestions about the proximate mechanisms that may allow familiar pair partners to mate earlier than unfamiliar partners. First, they may have improved coordination of their reproductive sexual cycles to reach receptivity earlier and thereby maximise fertilisation success. Second, they may forage more efficiently, benefiting from effective information transfer and/or cooperative predator detection. Those ideas need empirical testing in the future. Regardless of the mechanism, our observations of sleepy lizard pairing behaviour support the mate familiarity hypothesis, but not the reproductive performance hypothesis, as an explanation for its long‐term monogamous mating system.

High Transmissibility During Early HIV Infection Among Men Who Have Sex With Men-San Francisco, California.

We estimate the relative transmission rate in early versus later infection among men who have sex with men (MSM) in San Francisco, California, by studying the characteristics of a sample of transmitters, recruited through newly diagnosed, recently infected MSM between 1996 and 2009. Of 36 transmitters identified, 9 were determined on the basis of testing history and serologic testing to have been recently infected. The unadjusted odds ratio of transmitting during early infection was 15.2 (95% confidence interval [CI], 6.3–33.4; P < .001); the odds ratio was 8.9 (95% CI, 4.1–19.4) after adjustment for self-reported antiretroviral treatment. This high transmissibility could be due to both high infectiousness and high rates of sex partner change or concurrent partnerships.

Looking upstream to prevent HIV transmission

High rates of partner change in 'upstream' sex work networks have long been recognized to drive 'downstream' transmission of sexually transmitted infections (STIs). We used a stochastic microsimulation model (STDSIM) to explore such transmission dynamics in a generalized African HIV epidemic. We refined the quantification of sex work in Kisumu, Kenya, from the 4-cities study. Interventions with sex workers were introduced in 2000 and epidemics projected to 2020. We estimated the contribution of sex work to transmission, and modelled standard condom and STI interventions for three groups of sex workers at feasible rates of use and coverage. Removing transmission from sex work altogether would have resulted in 66% lower HIV incidence (range 54-75%) and 56% lower prevalence (range 44-63%) after 20 years. More feasible interventions reduced HIV prevalence from one-fifth to one-half. High rates of condom use in sex work had the greatest effect, whereas STI treatment contributed to HIV declines at lower levels of condom use. Interventions reaching the 40% of sex workers with most clients reduced HIV transmission nearly as much as less targeted approaches attempting to reach all sex workers. Declines were independent of antiretroviral therapy rollout and robust to realistic changes in parameter values. 'Upstream' transmission in sex work remains important in advanced African HIV epidemics even in the context of antiretroviral therapy. As in concentrated Asian epidemics, feasible condom and STI interventions that reach the most active sex workers can markedly reduce the size of HIV epidemics. Interventions targeting 'transactional' sex with fewer clients have less impact.

Sexual health in adolescents

Young people are particularly vulnerable to poor sexual health outcomes of high rates of sexually transmitted infections (STIs) and unwanted pregnancy. They partake in riskier sexual behaviors with higher rates of sexual partner change and poor levels of contraception, including condom use. Access to services may be limited either through lack of appropriate services or disinclination to seek out services. We review the biological, cognitive, behavioral, and socioeconomic risk factors that contribute to their poor sexual health outcomes. Details include the epidemiology, presentation and complications of STIs and pregnancy in adolescents, the clinical assessment of adolescents, contraception options, confidentiality, consent and safeguarding, and key characteristics of successful adolescent services.

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.

The Prevalence of HIV by Ethnic Group Is Correlated with HSV-2 and Syphilis Prevalence in Kenya, South Africa, the United Kingdom, and the United States.

Background. This paper investigates two issues: do ethnic/racial groups with high HIV prevalences also have higher prevalences of other STIs? and is HIV prevalence by ethnic group correlated with the prevalence of circumcision, concurrency, or having more than one partner in the preceding year? Methods. We used Spearman's correlation to estimate the association between the prevalence of HIV per ethnic/racial group and HSV-2, syphilis, symptoms of an STI, having more than one partner in the past year, concurrency, and circumcision in Kenya, South Africa, the United Kingdom, and the United States. Results. We found that in each country HSV-2, syphilis, and symptomatic STIs were positively correlated with HIV prevalence (HSV-2: Kenya rho = 0.50, P = 0.207; South Africa rho-1, P = 0.000; USA rho-1, P = 0.000, Syphilis: Kenya rho = 0.33, P = 0.420; South Africa rho-1, P = 0.000; USA rho-1, P = 0.000, and STI symptoms: Kenya rho = 0.92, P = 0.001; South Africa rho-1, P = 0.000; UK rho = 0.87, P = 0.058; USA rho-1, P = 0.000). The prevalence of circumcision was only negatively associated with HIV prevalence in Kenya. Both having more than one partner in the previous year and concurrency were positively associated with HIV prevalence in all countries (concurrency: Kenya rho = 0.79, P = 0.036; South Africa rho-1, P = 0.000; UK 0.87, P = 0.058; USA rho-1, P = 0.000 and multiple partners: Kenya rho = 0.82, P = 0.023; South Africa rho-1, P = 0.000; UK rho = 0.87, P = 0.058; USA rho-1, P = 0.000). Not all associations were statistically significant. Conclusion. Further attention needs to be directed to what determines higher rates of partner change and concurrency in communities with high STI prevalence.