Determinants of the impact of sexually transmitted infection treatment on prevention of HIV infection: a synthesis of evidence from the Mwanza, Rakai, and Masaka intervention trials

Anal sexually transmitted infections and risk of HIV infection in homosexual men

BACKGROUND

We examined a range of common bacterial and viral sexually transmitted infections as risk factors for HIV seroconversion in a community-based cohort of HIV-negative homosexual men in Sydney, Australia.

METHODS

Detailed information about HIV risk behaviors was collected by interview twice yearly. Participants were tested annually for HIV, anal and urethral gonorrhea and chlamydia, herpes simplex virus types 1 and 2, and syphilis. In addition, they reported annual diagnoses of these conditions and of genital and anal warts.

RESULTS

Among 1427 enrolled participants, 53 HIV seroconverters were identified, giving an incidence of 0.78 per 100 person-years. After controlling for number of episodes of insertive and receptive nonseroconcordant unprotected anal intercourse, there were independent associations with anal gonorrhea (adjusted hazard ratio = 7.12, 95% confidence interval: 2.05 to 24.79) and anal warts (hazard ratio = 3.63, 95% confidence interval: 1.62 to 8.14).

CONCLUSIONS

Anal gonorrhea and anal warts were independently associated with HIV acquisition. The added HIV prevention value of more frequent screening of the anus to allow early detection and treatment of anal sexually transmitted infections in homosexual men should be considered.

Cluster randomized trials for HIV prevention

PURPOSE OF REVIEW

This paper reviews cluster randomized trials for HIV prevention, focusing on the unique aspects of such trials and describes key cluster randomized trials for HIV prevention from the past decade. Relevant methodological issues are also reviewed.

RECENT FINDINGS

Three cluster randomized trials evaluating sexually transmitted infection control as an HIV prevention tool have given mixed results. Recent modeling studies suggest that the differences are due to differences in the underlying populations rather than design differences. Two trials have shown reduced HIV incidence in intervention target groups without showing a community-wide effect. Areas of active methodological research include ensuring baseline comparability between arms in cluster randomized trials with relatively few clusters, and measuring incidence when the intervention may require time to be fully effective. Innovative approaches to measuring incidence based on so-called 'detuned assays' may be relevant to this problem.

SUMMARY

Cluster randomized trials are qualitatively different from individually randomized trials. As the intervention population may differ from the assessment population, cluster randomized trials of infectious diseases can estimate both direct and indirect intervention effects. Most cluster randomized trial interventions involve behavioral or social components, so the generalizability of results to other settings is often difficult. Modeling studies can aid in the interpretation of results.

Addressing the migration of health professionals: the role of working conditions and educational placements

This article provides a brief overview of the global health-worker shortage, which could undermine the Millennium Development Goal to halt and begin to reverse the spread of HIV/AIDS. The current situation suggests that long-term solutions to shortages can only be found by addressing the problem from a global perspective; that is, to eliminate shortages through substantial investments in training and retaining health workers in developed and developing countries, and not through policies that do not work towards solving this underlying problem, such as ones that restrict migration.

Sexual transmission of HIV-1

HIV-1 transmission occurs in a limited number of ways all of which are preventable. Overall, the risk of HIV-1 transmission following a single sexual exposure is low especially in comparison with other sexually transmitted infections (STIs); with estimates of the average probability of male to female HIV-1 transmission only 0.0005-0.0026 per coital act. The risk of acquiring HIV-1 from a single contact varies enormously and is dependant upon the infectiousness of the HIV-1 positive individual and the susceptibility to HIV-1 of their sexual partner. An understanding of the determinants of HIV-1 transmission is important not only to assess the infection risk to an individual when exposed to the virus (e.g. to determine the provision of post exposure prophylaxis), but also to make accurate predictions on the potential spread of HIV-1 infection in a population and to direct appropriate targeted prevention strategies. In this review article we summarise the current literature on the major worldwide source of HIV-1 acquisition, sexual transmission. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.

Rethinking the role of the local community in HIV epidemic spread in sub-Saharan Africa: a proximate-determinants approach

The spread of HIV in sub-Saharan Africa continues largely unabated. To improve prevention interventions, a better understanding of the determinants of HIV infection is required. Conceptual frameworks can guide epidemiological investigation and prevent a misguided focus on single risk factors in isolation. Existing frameworks of HIV infection focus on transmission. However, the transmitting individual is rarely known. By contrast, data on individual HIV acquisition are available from longitudinal studies and tests for recent HIV infection. From the perspective of individuals susceptible to HIV, it is important to distinguish between factors determining the individual's biological disposition and sexual behavior and community-level factors, which can affect both HIV acquisition and the likelihood that a sex partner chosen from a community will be infected with HIV and transmit the infection. We propose a framework that takes the susceptible individual as a starting point and links distal, proximate and biological determinants of HIV infection at both the individual and the community level. We describe three necessary ingredients for the use of the framework (identification of the relevant community, multilevel analysis and methods for causal inference).

Discussion and revision of the mathematical modeling tool described in the previously published article "Modeling HIV Transmission risk among Mozambicans prior to their initiating highly active antiretroviral therapy"

Mathematical models are increasingly used in social and behavioral studies of HIV transmission; however, model structures must be chosen carefully to best answer the question at hand and conclusions must be interpreted cautiously. In Pearson et al. (2007), we presented a simple analytically tractable deterministic model to estimate the number of secondary HIV infections stemming from a population of HIV-positive Mozambicans and to evaluate how the estimate would change under different treatment and behavioral scenarios. In a subsequent application of the model with a different data set, we observed that the model produced an unduly conservative estimate of the number of new HIV-1 infections. In this brief report, our first aim is to describe a revision of the model to correct for this underestimation. Specifically, we recommend adjusting the population-level sexually transmitted infection (STI) parameters to be applicable to the individual-level model specification by accounting for the proportion of individuals uninfected with an STI. In applying the revised model to the original data, we noted an estimated 40 infections/1000 HIV-positive persons per year (versus the original 23 infections/1000 HIV-positive persons per year). In addition, the revised model estimated that highly active antiretroviral therapy (HAART) along with syphilis and herpes simplex virus type 2 (HSV-2) treatments combined could reduce HIV-1 transmission by 72% (versus 86% according to the original model). The second aim of this report is to discuss the advantages and disadvantages of mathematical models in the field and the implications of model interpretation. We caution that simple models should be used for heuristic purposes only. Since these models do not account for heterogeneity in the population and significantly simplify HIV transmission dynamics, they should be used to describe general characteristics of the epidemic and demonstrate the importance or sensitivity of parameters in the model.

Fitting the HIV epidemic in Zambia: a two-sex micro-simulation model

BACKGROUND

In describing and understanding how the HIV epidemic spreads in African countries, previous studies have not taken into account the detailed periods at risk. This study is based on a micro-simulation model (individual-based) of the spread of the HIV epidemic in the population of Zambia, where women tend to marry early and where divorces are not frequent. The main target of the model was to fit the HIV seroprevalence profiles by age and sex observed at the Demographic and Health Survey conducted in 2001.

METHODS AND FINDINGS

A two-sex micro-simulation model of HIV transmission was developed. Particular attention was paid to precise age-specific estimates of exposure to risk through the modelling of the formation and dissolution of relationships: marriage (stable union), casual partnership, and commercial sex. HIV transmission was exclusively heterosexual for adults or vertical (mother-to-child) for children. Three stages of HIV infection were taken into account. All parameters were derived from empirical population-based data. Results show that basic parameters could not explain the dynamics of the HIV epidemic in Zambia. In order to fit the age and sex patterns, several assumptions were made: differential susceptibility of young women to HIV infection, differential susceptibility or larger number of encounters for male clients of commercial sex workers, and higher transmission rate. The model allowed to quantify the role of each type of relationship in HIV transmission, the proportion of infections occurring at each stage of disease progression, and the net reproduction rate of the epidemic (R(0) = 1.95).

CONCLUSIONS

The simulation model reproduced the dynamics of the HIV epidemic in Zambia, and fitted the age and sex pattern of HIV seroprevalence in 2001. The same model could be used to measure the effect of changing behaviour in the future.

Principles of Infectious Disease Epidemiology

In this chapter, principles and concepts of modern infectious disease epidemiology Epidemiology are presented. We delineate the role of epidemiology for public health and discuss the characteristics of infectious disease epidemiology. This chapter also includes definitions of important terms used in infectious disease epidemiology.

Left out but not forgotten: Should closer attention be paid to coinfection with herpes simplex virus type 1 and HIV?

Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) are among the most common coinfections seen in individuals infected with HIV-1. Most research on HSV-HIV coinfection has focused on HSV-2, and in particular, on its impact on HIV transmission. HSV-2 is associated with micro- and macroulcerations in genital mucosal surfaces, increased numbers of HIV target cells in genital mucosal tissue and increases in plasma HIV viral load of up to 0.5 log(10) copies/mL, such that HSV-2 infection increases the risk of both HIV acquisition and transmission. Because plasma HIV RNA levels are a major determinant of rates of CD4 cell decline, HSV-2 coinfection may also adversely affect the progression of HIV disease. Anti-HSV medications have in fact been associated with reciprocal decreases in HIV viral load in short-term studies. These findings have led to the development of several clinical trials of HSV-2 suppression as strategies for preventing HIV transmission and slowing the rate of HIV disease progression. HSV-1 coinfection has largely been ignored from this growing body of research, yet there are several reasons that this coinfection remains an important issue for study. First, the seroprevalence of HSV-1 is consistently higher than that of HSV-2 among both HIV-infected and HIV-uninfected populations, underscoring the relevance of HSV-1 coinfection to the majority of HIV-infected persons. Second, pre-existing HSV-1 antibodies in individuals may modulate the course of subsequently acquired HSV-2 infection; the implications of such changes on HSV-HIV coinfection remain unexplored. Third, HSV-1 and HSV-2 are closely related viruses that share 83% genetic homology. Their virological and pathobiological similarities suggest that their implications on HIV pathogenesis may be similar as well. Finally, HSV-1 is becoming increasingly relevant because the incidence of genital HSV-1 has risen. Although genital herpes is traditionally associated with HSV-2, recent studies have shown that the majority of serologically confirmed primary genital herpes in some settings is attributable to HSV-1. Because the genital tract is an important site of biological interaction between HSV and HIV, this epidemiological change may be clinically important.

High-risk sexual behavior at social venues in Madagascar

BACKGROUND

Persistent high levels of sexually transmitted infection (STI) in Madagascar indicate current prevention strategies are inadequate. STI/HIV prevention based in social venues may play an important role in reaching individuals at risk of infection. We identified venues where people meet sexual partners and measured the need and potential for venue-based prevention.

METHODS

Interviews were conducted in 7 Madagascar towns with 1) community informants to identify social venues, 2) individuals socializing at a sample of venues to assess sexual behavior among venue patrons, and 3) venue representatives to assess the potential for venue-based intervention.

RESULTS

Community informants identified numerous venues (range: 67-211 venues, depending on the town); streets, bars, and hotels were most commonly reported. Among 2982 individuals socializing at venues, 78% of men and 74% of women reported new sexual partnership or sex trade for money, goods, or services in the past 4 weeks and 19% of men and 18% of women reported symptoms suggestive of STI in the past 4 weeks. STI symptom levels were disproportionately high among respondents reporting either sex trade or new sexual partnership in the past 4 weeks. Twenty-eight percent of men and 41% of women reported condom use during the last sex act with a new partner. Although 24% to 45% of venues had hosted STI/HIV interventions, interventions were deemed possible at 73% to 90% venues according to 644 interviews with venue representatives.

CONCLUSIONS

Venue-based intervention is possible and would reach a spectrum of populations vulnerable to STI/HIV including sex workers, their clients, and other high-risk populations.

Population-level effect of HSV-2 therapy on the incidence of HIV in sub-Saharan Africa

BACKGROUND

Herpes simplex virus type 2 (HSV-2) infection increases acquisition and transmission of HIV, but the results of trials measuring the impact of HSV-2 therapy on HIV genital shedding and HIV acquisition are mixed, and the potential impact of HSV-2 therapy on the incidence of HIV at the population level is unknown.

METHODS

The effects of episodic and suppressive HSV-2 therapy were simulated using the individual-level model STDSIM fitted to data from Cotonou, Benin (relatively low HIV prevalence) and Kisumu, Kenya (high HIV prevalence). Clinician- and patient-initiated episodic therapy, started when symptomatic, were assumed to reduce ulcer duration. Suppressive therapy, given regardless of symptoms, was also assumed to reduce ulcer frequency and HSV-2 infectiousness.

RESULTS

Clinician-initiated episodic therapy in the general population had almost no effect on the incidence of HIV. The impact of patient-initiated therapy was higher because of earlier treatment initiation, but still low (<5%) unless symptom recognition and treatment-seeking behaviour were very high. Suppressive therapy given to female sex workers (FSW) in Kisumu had little effect on population HIV incidence. In Cotonou, suppressive therapy in FSW with high coverage and long duration reduced population HIV incidence by >20% in the long term. Impact was increased in both cities by also treating a proportion of their clients. Long-term suppressive therapy with high coverage in the general population could reduce HIV incidence by more than 30%.

CONCLUSIONS

These results show that HSV-2 therapy could potentially have a population-level impact on the incidence of HIV, especially in more concentrated epidemics. However, a substantial impact requires high coverage and long duration therapy, or very high symptom recognition and treatment-seeking behaviour.

Male circumcision for HIV prevention in sub-Saharan Africa: who, what and when?

BACKGROUND AND OBJECTIVE

Male circumcision (circumcision) reduces HIV incidence in men by 50-60%. The United Nations Joint Programme on HIV/AIDS (UNAIDS) recommends the provision of safe circumcision services in countries with high HIV and low circumcision prevalence, prioritizing 12-30 years old HIV-uninfected men. We explore how the population-level impact of circumcision varies by target age group, coverage, time-to-scale-up, level of risk compensation and circumcision of HIV infected men.

DESIGN AND METHODS

An individual-based model was fitted to the characteristics of a typical high-HIV-prevalence population in sub-Saharan Africa and three scenarios of individual-level impact corresponding to the central and the 95% confidence level estimates from the Kenyan circumcision trial. The simulated intervention increased the prevalence of circumcision from 25 to 75% over 5 years in targeted age groups. The impact and cost-effectiveness of the intervention were calculated over 2-50 years. Future costs and effects were discounted and compared with the present value of lifetime HIV treatment costs (US$ 4043).

RESULTS

Initially, targeting men older than the United Nations Joint Programme on HIV/AIDS recommended age group may be the most cost-effective strategy, but targeting any adult age group will be cost-saving. Substantial risk compensation could negate impact, particularly if already circumcised men compensate. If circumcision prevalence in HIV uninfected men increases less because HIV-infected men are also circumcised, this will reduce impact in men but would have little effect on population-level impact in women.

CONCLUSION

Circumcision is a cost-saving intervention in a wide range of scenarios of HIV and initial circumcision prevalence but the United Nations Joint Programme on HIV/AIDS/WHO recommended target age group should be widened to include older HIV-uninfected men and counselling should be targeted at both newly and already circumcised men to minimize risk compensation. To maximize infections-averted, circumcision must be scaled up rapidly while maintaining quality.

Biomedical interventions to prevent HIV infection: evidence, challenges, and way forward

Intensive research efforts for more than two decades have not yet resulted in an HIV vaccine of even moderate effectiveness. However, some progress has been made with other biomedical interventions, albeit on the basis of inconsistent levels of evidence. The male condom, if used correctly and consistently, has been proven in observational studies to be very effective in blocking HIV transmission during sexual intercourse; and, in three randomised trials, male circumcision was protective against HIV acquisition among men. Treatment of sexually transmitted infections, a public health intervention in its own right, has had mixed results, depending in part on the epidemic context in which the approach was assessed. Finally, oral and topical antiretroviral compounds are being assessed for their role in reduction of HIV transmission during sexual intercourse. Research on biomedical interventions poses formidable challenges. Difficulties with product adherence and the possibility of sexual disinhibition are important concerns. Biomedical interventions will need to be part of an integrative package that includes biomedical, behavioural, and structural interventions. Assessment of such multicomponent approaches with moderate effects is difficult. Issues to be considered include the nature of control groups and the effect of adherence on the true effectiveness of the intervention.

Low effectiveness of syndromic treatment services for curable sexually transmitted infections in rural South Africa

Objectives:

Syndromic sexually transmitted infection (STI) treatment remains a cost-saving HIV prevention intervention in many countries in Africa. We estimate the effectiveness of syndromic treatment for curable STIs in rural KwaZulu-Natal, South Africa, and the trend in STI prevalences before and after the introduction of syndromic treatment in 1995.

Methods:

Data were available from various clinical studies, surveys of public and private health providers, the general population and women attending antenatal, family planning and child immunisation clinics in rural northern KwaZulu-Natal between 1987 and 2004. Overall effectiveness was defined as the estimated proportion of the annual number of symptomatic curable STI episodes cured by syndromic treatment based on separate estimates for six curable STI aetiologies by gender.

Results:

Median overall effectiveness was 13.1% (95% CI 8.9 to 17.8%) of symptomatic curable STI episodes cured. Effectiveness increased to 25.0% (95% CI 17.3 to 33.8%), 47.6% (95% CI 44.5 to 50.8%) or 14.3% (95% CI 9.9 to 19.4%) if 100% treatment seeking, 100% correct treatment provision or 100% cure were assumed, respectively. Time-trends were difficult to assess formally but there was little evidence of decreasing STI prevalences. Including incurable but treatable herpes simplex virus (HSV)-2 ulcers in the effectiveness calculation would halve the proportion of ulcers cured or correctly treated, but this reduction could be entirely countered by including episodic antiviral treatment in the national guidelines.

Conclusion:

Overall effectiveness of syndromic treatment for curable STIs in rural KwaZulu-Natal remains low and there is little evidence of reduced curable STI prevalences. As syndromic treatment is likely to be a cost-saving HIV prevention intervention in South Africa, innovative strategies are urgently needed to increase rates of treatment seeking and correct treatment provision.

Prevalence and incidence of sexually transmitted infections among South Indians at increased risk of HIV infection

Sexually transmitted infections (STIs) have been identified as cofactors of HIV transmission. Greater understanding of local STI burdens can assist in the development of more effective STI and HIV prevention strategies. The aim of this study is to determine the prevalence and incidence of STIs among South Indian men and women identified to be at increased risk for HIV infection. Individuals at increased risk for HIV infection were enrolled in a prospective longitudinal study in Chennai, India (n = 480) between August 2002 and December 2003. Participants were enrolled from patients seeking services at an sexually transmitted disease (STD) clinic and a confidential HIV testing and counseling program. The most common prevalent STIs were herpes simplex virus (HSV)-2 (50% of women, 29% of men), syphilis (11% of women, 8% of men), and Trichomonas vaginalis (6% of women). At enrollment, women, participants with no schooling, participants with greater than four sex partners, and single participants were found to be at increased risk for HSV-2 infection (p < 0.05). The two most common incident STIs at 12 months were HSV-2 with 12% of men and 8% of women testing positive and hepatitis B with 2% of men and 5% of women testing hepatitis B surface antigen (HBsAg) positive. In this cohort of South Indian men and women with a high background prevalence of HSV-2, suppressive therapy against herpes replication may have a substantial impact in reducing both HSV-2 transmission and HIV acquisition. With the high incidence of STIs, targeted prevention and clinical management strategies among individuals practicing high risk behaviors may help to slow the continued spread of HIV in India.

Persisting with prevention: the importance of adherence for HIV prevention

BACKGROUND

Only four out of 31 completed randomized controlled trials (RCTs) of HIV prevention strategies against sexual transmission have shown significant efficacy. Poor adherence may have contributed to the lack of effect in some of these trials. In this paper we explore the impact of various levels of adherence on measured efficacy within an RCT.

ANALYSIS

We used simple quantitative methods to illustrate the impact of various levels of adherence on measured efficacy by assuming a uniform population in terms of sexual behavior and the binomial model for the transmission probability per partnership.At 100% adherence the measured efficacy within an RCT is a reasonable approximation of the true biological efficacy. However, as adherence levels fall, the efficacy measured within a trial substantially under-estimates the true biological efficacy. For example, at 60% adherence, the measured efficacy can be less than half of the true biological efficacy.

CONCLUSION

Poor adherence during a trial can substantially reduce the power to detect an effect, and improved methods of achieving and maintaining high adherence within trials are needed. There are currently 12 ongoing HIV prevention trials, all but one of which require ongoing user-adherence. Attention must be given to methods of maximizing adherence when piloting and designing RCTs and HIV prevention programmes.

The spread, treatment, and prevention of HIV-1: evolution of a global pandemic

The most up-to-date estimates demonstrate very heterogeneous spread of HIV-1, and more than 30 million people are now living with HIV-1 infection, most of them in sub-Saharan Africa. The efficiency of transmission of HIV-1 depends primarily on the concentration of the virus in the infectious host. Although treatment with antiviral agents has proven a very effective way to improve the health and survival of infected individuals, as we discuss here, the epidemic will continue to grow unless greatly improved prevention strategies can be developed and implemented. No prophylactic vaccine is on the horizon. However, several behavioral and structural strategies have made a difference--male circumcision provides substantial protection from sexually transmitted diseases, including HIV-1, and the application of antiretroviral agents for prevention holds great promise.

Screening for genital and anorectal sexually transmitted infections in HIV prevention trials in Africa

OBJECTIVES

To demonstrate the value of routine, basic sexually transmitted infection (STI) screening at enrolment into an HIV-1 vaccine feasibility cohort study and to highlight the importance of soliciting a history of receptive anal intercourse (RAI) in adults identified as "high risk".

METHODS

Routine STI screening was offered to adults at high risk of HIV-1 upon enrolment into a cohort study in preparation for HIV-1 vaccine trials. Risk behaviours and STI prevalence were summarised and the value of microscopy assessed. Associations between prevalent HIV-1 infection and RAI or prevalent STI were evaluated with multiple logistic regression.

RESULTS

Participants had a high burden of untreated STI. Symptom-directed management would have missed 67% of urethritis cases in men and 59% of cervicitis cases in women. RAI was reported by 36% of male and 18% of female participants. RAI was strongly associated with HIV-1 in men (adjusted odds ratio (aOR) 3.8; 95% CI 2.0 to 6.9) and independently associated with syphilis in women (aOR 12.9; 95% CI 3.4 to 48.7).

CONCLUSIONS

High-risk adults recruited for HIV-1 prevention trials carry a high STI burden. Symptom-directed treatment may miss many cases and simple laboratory-based screening can be done with little cost. Risk assessment should include questions about anal intercourse and whether condoms were used. STI screening, including specific assessment for anorectal disease, should be offered in African research settings recruiting participants at high risk of HIV-1 acquisition.

Treating curable sexually transmitted infections to prevent HIV in Africa: still an effective control strategy?

BACKGROUND

Evidence regarding the effectiveness of sexually transmitted infection (STI) treatment for HIV prevention in Africa is equivocal, leading some policy makers to question whether it should continue to be promoted for HIV control. We explore whether treating curable STIs remains a cost-effective HIV control strategy in Africa.

METHODS

The model STDSIM was fitted to the characteristics of 4 populations in East and West Africa. Over the simulated HIV epidemics, the population-attributable fractions (PAFs) of incident HIV attributable to STIs, the impact of syndromic STI management on HIV incidence, and the cost per HIV infection averted were evaluated and compared with an estimate of lifetime HIV treatment costs (US $3500).

RESULTS

Throughout the HIV epidemics in all cities, the total PAF for. all STIs remained high, with > or = 50% of HIV transmission attributed to STIs. The PAF for herpes simplex virus type 2 increased during the epidemics, whereas the PAF for curable STIs and the relative impact of syndromic management decreased. The models showed that the absolute impact of syndromic management remains high in generalized epidemics, and it remained cost-saving in 3 of the 4 populations in which the cost per HIV infection averted ranged between US $321 and $1665.

CONCLUSION

Curable STI interventions may remain cost-saving in populations with generalized HIV epidemics, particularly in populations with high-risk behaviors or low male circumcision rates.

Reproductive tract infections among women attending a gynecology outpatient department in Vientiane, Lao PDR

OBJECTIVES AND GOAL

To clinically and microbiologically identify reproductive tract infections (RTI), including sexually transmitted infections (STI), and to monitor the antibiotic susceptibility of Neisseria gonorrhoeae among women attending a gynecology outpatient department in Vientiane, Laos.

STUDY DESIGN

Clinical and laboratory-based cross-sectional study. Women aged 15 to 49 years underwent a pelvic examination, and specimens were taken for laboratory testing.

RESULTS

Of 1125 study participants, 82% clinically presented with an RTI syndrome. However, only 64% had an etiologically diagnosed RTI, including 11% with an STI. Endogenous infections were most prevalent (candidiasis 40%; bacterial vaginosis 25%), followed by STI [Chlamydia trachomatis 4.1%; N. gonorrhoeae (NG) and Trichomonas vaginalis, both 3.7%]. The 41 NG isolates showed 20% resistance to ciprofloxacin, 98% to penicillin, and complete to tetracycline.

CONCLUSIONS

High RTI/STI level combined with high NG resistance emphasizes that concurrent with syndromic case management, periodic evaluations of etiological diagnosis should be available to ensure adequacy of treatment algorithms and prescribed medications.

Identification of novel risks for nonulcerative sexually transmitted infections among young men in Kisumu, Kenya

OBJECTIVES

STI prevention interventions often aim to reduce HIV incidence. Understanding STI risks may lead to more effective HIV prevention.

GOAL

To identify STI risks among men aged 18-24 in Kisumu, Kenya.

STUDY DESIGN

We analyzed baseline data from a randomized trial of male circumcision. Participants were interviewed for sociodemographic and behavioral risks. Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) were diagnosed by polymerase chain reaction assay and Trichomonas vaginalis (TV) by culture. The outcome for logistic regression analysis was infection with NG, CT, or TV.

RESULTS

Among 2743 men, 214 (7.8%; 95% CI: 6.8%-8.8%) were infected with any STI. In multivariable analysis, statistically significant risks for infection were: living one's whole life in Kisumu (OR = 1.50; 95% CI: 1.12-2.01), preferring "dry" sex (OR = 1.47; 95% CI: 1.05-2.07), HSV-2 seropositivity (OR = 1.37; 95% CI: 1.01-1.86), and inability to ejaculate during sex (OR = 2.04; 95% CI: 1.15-3.62). Risk decreased with increasing age and education, and cleaning one's penis less than 1 hour after sex (OR = 0.51; 95% CI: 0.33-0.80).

CONCLUSION

Understanding how postcoital cleaning, "dry" sex, and sexual dysfunction relate to STI acquisition may improve STI and HIV prevention.

Evaluating large-scale HIV prevention interventions: study design for an integrated mathematical modelling approach

BACKGROUND

There is an urgent need to evaluate HIV prevention interventions, thereby improving our understanding of what works, under what circumstances and what is cost effective.

OBJECTIVES

To describe an integrated mathematical evaluation framework designed to assess the population-level impact of large-scale HIV interventions and applied in the context of Avahan, the Indian AIDS Initiative, in southern India. The Avahan Initiative is a large-scale HIV prevention intervention, funded by the Bill & Melinda Gates Foundation, which targets high-risk groups in selected districts of the six states most affected by the HIV/AIDS epidemic (Maharashtra, Karnataka, Tamil Nadu, Andhra Pradesh, Nagaland and Manipur) and along the national highways.

METHODS

One important component of the monitoring and evaluation of Avahan relies on an integrated mathematical framework that combines empirical biological and behavioural data from different subpopulations in the intervention areas, with the use of tailor-made transmission dynamics models embedded within a Bayesian framework.

RESULTS

An overview of the Avahan Initiative and the objectives of the monitoring and evaluation of the intervention is given. The rationale for choosing this evaluation design compared with other possible designs is presented, and the different components of the evaluation framework are described and its advantages and challenges are discussed, with illustrated examples.

CONCLUSIONS

This is the first time such an approach has been applied on such a large scale. Lessons learnt from the CHARME project could help in the design of future evaluations of large-scale interventions in other settings, whereas the results of the evaluation will be of programmatic and public health relevance.

The future of HIV prevention: control of sexually transmitted infections and circumcision interventions

Prevention and control of sexually transmitted infections (STIs) has proven effective in reducing HIV infection when treatment is available promptly for symptomatic persons in conditions of an emerging epidemic. Biologically, it is assumed that reduced genital tract inflammation reduces infectiousness for HIV as well as reducing susceptibility in HIV-uninfected persons. Male circumcision has been demonstrated effective in reducing risk for HIV infection in three separate trials from South Africa, Kenya, and Uganda. Global expansion of STI treatment and male circumcision programs are vital tools for control of HIV infection; current evidence is reviewed and research priorities are presented.

Could a simple antenatal package combining micronutritional supplementation with presumptive treatment of infection prevent maternal deaths in sub-Saharan Africa?

BACKGROUND

Reducing maternal mortality is a key goal of international development. Our objective was to determine the potential impact on maternal mortality across sub-Saharan Africa of a combination of dietary supplementation and presumptive treatment of infection during pregnancy. Our aim was to demonstrate the importance of antenatal interventions in the fight against maternal mortality, and to stimulate debate about the design of an effective antenatal care package which could be delivered at the lowest level of the antenatal health system or at community level.

METHODS

We collated evidence for the effectiveness of antenatal interventions from systematic reviews and controlled trials, and we selected interventions which have demonstrated potential to prevent maternal deaths. We used a model-based analysis to estimate the total reduction in maternal mortality in sub-Saharan Africa which could be achieved by combining these interventions into a single package, based on a WHO systematic review of causes of maternal deaths.

RESULTS

Severe hypertensive disorders, puerperal sepsis and anemia are causes of maternal deaths which could be prevented to some extent by prophylactic measures during pregnancy. A package of pills comprising calcium and iron supplements and appropriate anti-microbial and anti-malarial drugs could reduce maternal mortality in sub-Saharan Africa by 8% (range <1% to 20%). This estimate is based on Cochrane Review estimates for the effectiveness of daily calcium supplements in reducing the risk of death/serious morbidity due to hypertensive disorders (RR = 0.80, 95% CI 0.65-0.97), anti-microbial prophylaxis in reducing the odds of puerperal sepsis/postpartum endometritis (OR = 0.49, 95% CI 0.23-1.06), anti-malarial prophylaxis in reducing the risk of severe antenatal anemia (RR = 0.62, 95% CI 0.50-0.78), and iron supplementation in reducing the risk of iron deficiency anemia at term (RR = 0.33, 95% CI 0.16-0.69).

CONCLUSION

Maternal mortality could be reduced by a combination of micronutrient supplementation and presumptive treatment of infection during pregnancy. Such an approach could be adopted in resource-poor settings where visits to antenatal clinics are infrequent and would complement existing Safe Motherhood activities.

Modeling HIV transmission risk among Mozambicans prior to their initiating highly active antiretroviral therapy

Understanding sexual behavior and assessing transmission risk among people living with HIV-1 is crucial for effective HIV-1 prevention. We describe sexual behavior among HIV-positive persons initiating highly active antiretroviral therapy (HAART) in Beira, Mozambique. We present a Bernoulli process model (tool available online) to estimate the number of sexual partners who would acquire HIV-1 as a consequence of sexual contact with study participants within the prior three months. Baseline data were collected on 350 HAART-naive individuals 18-70 years of age from October 2004 to February 2005. In the three months prior to initiating HAART, 45% (n = 157) of participants had sexual relationships with 191 partners. Unprotected sex occurred in 70% of partnerships, with evidence suggesting unprotected sex was less likely with partners believed to be HIV-negative. Only 26% of the participants disclosed their serostatus to partners with a negative or unknown serostatus. Women were less likely to report concurrent relationships than were men (21 versus 66%; OR 0.13; 95%CI: 0.06, 0.26). Given baseline behaviors, the model estimated 23.2 infections/1,000 HIV-positive persons per year. The model demonstrated HAART along with syphilis and herpes simplex virus type 2 (HSV-2) treatment combined could reduce HIV-1 transmission by 87%; increasing condom use could reduce HIV-1 transmission by 67%.

Could the CARE-SHAKTI intervention for injecting drug users be maintaining the low HIV prevalence in Dhaka, Bangladesh?

AIMS

To explore whether the low HIV prevalence observed in Bangladesh results from prevention activities, this study uses mathematical modelling to estimate the impact of a needle/syringe exchange intervention for injecting drug users (IDUs) in Dhaka, Bangladesh.

DESIGN

Epidemiological, behavioural and intervention monitoring data were used to parameterize a dynamic mathematical model, and fit it to National HIV Sero-surveillance data among IDUs (2000-02). The model was used to estimate the impact of the intervention on HIV transmission among IDUs and their sexual partners.

SETTING

Dhaka, Bangladesh, where the HIV prevalence has remained low despite high-risk sexual and injecting behaviours, and growing HIV epidemics in neighbouring countries.

FINDINGS

The model predicts that the intervention may have reduced the incidence of HIV among IDUs by 90% (95% CI 74-94%), resulting in an IDU HIV prevalence of 10% (95% CI 4-19%) after 8 years of intervention activity instead of 42% (95% CI 30-47%) if the intervention had not occurred.

CONCLUSIONS

The analysis highlights the potential for rapid HIV spread among IDUs in Dhaka, and suggests that the intervention may have substantially reduced IDU HIV transmission. However, there is no room for complacency. Sustained and expanded funding for interventions in Dhaka and other regions of Bangladesh are crucial to maintaining the low HIV prevalence.

Global control of sexually transmitted infections

Sexually transmitted infections other than HIV are important global health issues. They have, however, been neglected as a public-health priority and control efforts continue to fail. Sexually transmitted infections, by their nature, affect individuals, who are part of partnerships and larger sexual networks, and in turn populations. We propose a framework of individual, partnership, and population levels for examining the effects of sexually transmitted infections and interventions to control them. At the individual level we have a range of effective diagnostic tests, treatments, and vaccines. These options are unavailable or inaccessible in many resource-poor settings, where syndromic management remains the core intervention for individual case management. At the partnership level, partner notification and antenatal syphilis screening have the potential to prevent infection and re-infection. Interventions delivered to whole populations, or groups in whom the risks of infection and onward transmission are very high, have the greatest potential effect. Improvements to the infrastructure of treatment services can reduce the incidence of syphilis and gonorrhoea or urethritis. Strong evidence for the effectiveness of most other interventions on population-level outcomes is, however, scarce. Effective action requires a multifaceted approach including better basic epidemiological and surveillance data, high quality evidence about effectiveness of individual interventions and programmes, better methods to get effective interventions onto the policy agenda, and better advocacy and more commitment to get them implemented properly. We must not allow stigma, prejudice, and moral opposition to obstruct the goals of infectious disease control.

Cost-effectiveness of male circumcision for HIV prevention in a South African setting

BACKGROUND

Consistent with observational studies, a randomized controlled intervention trial of adult male circumcision (MC) conducted in the general population in Orange Farm (OF) (Gauteng Province, South Africa) demonstrated a protective effect against HIV acquisition of 60%. The objective of this study is to present the first cost-effectiveness analysis of the use of MC as an intervention to reduce the spread of HIV in sub-Saharan Africa.

METHODS AND FINDINGS

Cost-effectiveness was modeled for 1,000 MCs done within a general adult male population. Intervention costs included performing MC and treatment of adverse events. HIV prevalence was estimated from published estimates and incidence among susceptible subjects calculated assuming a steady-state epidemic. Effectiveness was defined as the number of HIV infections averted (HIA), which was estimated by dynamically projecting over 20 years the reduction in HIV incidence observed in the OF trial, including secondary transmission to women. Net savings were calculated with adjustment for the averted lifetime duration cost of HIV treatment. Sensitivity analyses examined the effects of input uncertainty and program coverage. All results were discounted to the present at 3% per year. For Gauteng Province, assuming full coverage of the MC intervention, with a 2005 adult male prevalence of 25.6%, 1,000 circumcisions would avert an estimated 308 (80% CI 189-428) infections over 20 years. The cost is 181 dollars (80% CI 117-306 dollars) per HIA, and net savings are 2.4 million dollars (80% CI 1.3 million to 3.6 million dollars). Cost-effectiveness is sensitive to the costs of MC and of averted HIV treatment, the protective effect of MC, and HIV prevalence. With an HIV prevalence of 8.4%, the cost per HIA is 551 dollars (80% CI 344-1,071 dollars) and net savings are 753,000 (80% CI 0.3 million to 1.2 million dollars). Cost-effectiveness improves by less than 10% when MC intervention coverage is 50% of full coverage.

CONCLUSIONS

In settings in sub-Saharan Africa with high or moderate HIV prevalence among the general population, adult MC is likely to be a cost-effective HIV prevention strategy, even when it has a low coverage. MC generates large net savings after adjustment for averted HIV medical costs.

Strategies for global HIV prevention

Despite significant advances in the development of therapeutic strategies for HIV over the past 25 years, the AIDS pandemic continues to grow worldwide. Access to life-saving medicines is not universal and there is a critical need for better prevention strategies. This review will highlight current research in the area of HIV prevention strategies, including preventive HIV vaccines, effective microbicides, treatment of sexually transmitted infections and the impact on HIV transmission, in addition to the role of male circumcision and pre-exposure prophylaxis with antiretroviral medications in HIV prevention.

Empirical Observations Underestimate the Proportion of Human Immunodeficiency Virus Infections Attributable to Sexually Transmitted Diseases in the Mwanza and Rakai Sexually Transmitted Disease Treatment Trials: Simulation Results

BACKGROUND AND OBJECTIVES

Population attributable fractions (PAF) from observational studies may under- or overestimate the contribution of cofactor sexually transmitted disease (STD) to human immunodeficiency virus (HIV) spread. Empirical PAF estimates from the Mwanza and Rakai trials indicated the proportion of HIV infections attributable to STDs was higher in Mwanza than Rakai.

GOAL OF THIS STUDY

Estimate the "true" proportion (PAFM) of HIV infections attributable to STDs in the Mwanza and Rakai STD trial populations and explore how the evaluated interventions prevented HIV infections.

STUDY DESIGN

The STDSIM model was used to simulate the 2 populations at the baseline of the trials (with no STD treatment interventions) and counterfactual scenarios in which STD cofactor effects on HIV spread were removed either at the start of the trials or 2, 10, and 20 years into the HIV epidemics. Similar methods were used to quantify the contribution of the cure of each STD to overall HIV impact in each site.

RESULTS

: In Mwanza, the highest PAFM for the effect of any single STD over the 2 years of the trial was due to chancroid (40%). The PAFM for all curable STD was 65%. In Rakai, herpes simplex virus type 2 (HSV-2) was the most important STD (PAFM = 23%); the PAFM for curable STD was 20%. In both sites, the proportion of new infections due to treatable STD decreased over time. The decrease was greater for Rakai, where a behavioral risk reduction that preceded the trial reduced STD prevalence. In both sites, the importance of HSV-2 increased later in the HIV epidemics and STD increased transmission of HIV more than acquisition of HIV. In the Mwanza trial, treatment of chancroid contributed most to preventing new HIV infections.

CONCLUSIONS

PAFs calculated from empirical data underestimated the contribution of STD to HIV spread in the Mwanza and Rakai trial populations because STD effects on HIV transmission (as opposed to acquisition) were not captured in the observationally based studies.

HIV/AIDS epidemiology, pathogenesis, prevention, and treatment

The HIV-1 pandemic is a complex mix of diverse epidemics within and between countries and regions of the world, and is undoubtedly the defining public-health crisis of our time. Research has deepened our understanding of how the virus replicates, manipulates, and hides in an infected person. Although our understanding of pathogenesis and transmission dynamics has become more nuanced and prevention options have expanded, a cure or protective vaccine remains elusive. Antiretroviral treatment has transformed AIDS from an inevitably fatal condition to a chronic, manageable disease in some settings. This transformation has yet to be realised in those parts of the world that continue to bear a disproportionate burden of new HIV-1 infections and are most affected by increasing morbidity and mortality. This Seminar provides an update on epidemiology, pathogenesis, treatment, and prevention interventions pertinent to HIV-1.

The importance of context: model projections on how microbicide impact could be affected by the underlying epidemiologic and behavioral situation in 2 African settings

OBJECTIVE

The objective of this study was to explore how a microbicide's HIV impact is affected by behavioral and epidemiologic factors in 2 African settings: Cotonou, Benin, and Hillbrow, South Africa.

METHODS

A mathematical model, fit to epidemiologic data from each setting, was used to estimate the HIV impact of introducing a microbicide with different HIV/sexually transmitted infection (STI) efficacies. Simulations were compared to explore how impact is affected by context.

RESULTS

Widespread microbicide use results in a greater relative reduction in HIV incidence in Cotonou, where HIV/STIs are less prevalent. Most infections averted are from commercial sex in Cotonou but noncommercial sex in Hillbrow. The microbicide's STI efficacy is important in determining its HIV impact in both settings, but especially in Cotonou where the microbicide's HIV impact was mainly the result of its STI efficacy.

CONCLUSIONS

It is important to develop and evaluate microbicides that are efficacious against STIs. However, even with the same patterns of use, a microbicide's impact and the importance of its STI efficacy will vary considerably between settings.

Antimicrobial self medication for reproductive tract infections in two provinces in Lao People's Democratic Republic

OBJECTIVES

To describe antimicrobial self medication for reproductive tract infections (RTI) including sexually transmitted infections (STI), and to explore the understanding and use of health information among the adult population self medicating with antimicrobials for RTI/STI in two provinces of Laos. This could contribute to quality improvement of RTI/STI management.

METHODS

Cross sectional community based study. Structured interviews (household survey) were conducted among 500 subjects aged 18 or more, who had used antimicrobials as self medication for RTI/STI during the past year. They were recruited among 3056 family members in Vientiane capital and Champasak province, divided equally between the two study sites, and between urban and rural areas.

RESULTS

Among the 500 respondents reporting self medication for RTI/STI, 91% had bought the antimicrobials from local private pharmacies without a physician's prescription. 58% of those were advised to buy the drugs from drug sellers. Ampicillin (not recommended as syndromic treatment for RTI/STI) was used in 83% of all cases, in 28% combined with tetracycline. 79% of respondents used antimicrobials for a non-recommended duration of time. Most respondents had access to health messages for RTI/STI, largely from radio/television and drug sellers. However, only 17% of all respondents reported that they had ever used a condom.

CONCLUSIONS

More than three quarters of respondents, self medicating for RTI/STI with antimicrobials, used inappropriate drugs bought from private pharmacies. There is a need to improve RTI/STI management, including health promotion, through interventions at community level, and to health providers, including private drug sellers.

Reproductive rights and HIV/AIDS

Reproductive and sexual rights are at the centre of the acquired immunodeficiency syndrome (AIDS) epidemic through culturally defined gender roles, gender-based violence and limited access to quality health care. AIDS control is one of the Millennium Goals, and the '3-by-5' initiative [antiretroviral (ARV) therapy for all in need by 2005] is far from reaching its target. Apart from the reduction in morbidity and mortality due to antiretroviral (ARV) therapy, proven effective interventions for reproductive health include consistent condom use, voluntary counselling and testing, promoting earlier treatment and adhesion to preventative measures, and the use of ARV therapy, Caesarean section and bottle-feeding to reduce vertical transmission. The effectiveness of control of sexually transmitted infection is dependent on the maturity of the AIDS epidemic, but is an essential intervention due to other serious consequences for sexual and reproductive health. Male circumcision is a polemic preventive measure under debate, and microbicide products, a promising women-controlled method, are still undergoing efficacy trials. A reasonably organized and accessible health sector, the involvement of males in reproductive health debate and a gender-sensitive, rights-based political agenda, with ample participation of communities, are necessary for reproductive health interventions to move from proved efficacy to necessary effectiveness, putting evidence into practice.

Human immunodeficiency virus and other sexually transmitted diseases in Cuban women

A cross-sectional study was performed in 60 Cuban women of child-bearing age who were seropositive for human immunodeficiency virus (HIV) and 60 controls. Human papillomavirus (HPV) was identified most frequently, with oncogenic HPV serotypes 16, 33 and 58 detected in HIV-positive patients, and serotypes 11, 33 and 51 in the controls (relative risk 4.41; 95% CI 2.21-8.29). Syphilis and hepatitis B and C viruses were detected exclusively in HIV-seropositive women (p<0.05). Sexually transmitted diseases (STDs) appeared to pose a substantial health problem, especially for HIV-positive women. Clinics should consider screening and treatment for STDs as part of their HIV prevention programmes.

Developments in STD/HIV Interactions: The Intertwining Epidemics of HIV and HSV-2

Antiviral agents aimed at treating HSV-2 chronically infected individuals have proven to be effective in the prevention of symptomatic genital herpes and the reduction of viral shedding. These agents play a key role in current HIV prevention trials that will assess the role of suppression of HSV-2 infection on the risk for HIV acquisition and transmission. An added clinical benefit of treating HSV-2/HIV-coinfected individuals is the potential survival benefit, as suggested by earlier studies and by the recent findings that HSV-2/HIV dually infected individuals have higher viral loads. The results of the current HSV-2 suppression trials may provide additional tools to fight the global spread of HIV infection. Treatment of HSV-2/HIV dually infected individuals may prove to be a low-cost intervention to improve clinical outcomes and delay the need for antiretroviral therapy.

Randomized controlled trials of individual-level, population-level, and multilevel interventions for preventing sexually transmitted infections: what has worked?

BACKGROUND

Previous reviews of interventions to prevent sexually transmitted infections (STIs) focused mostly on human immunodeficiency virus (HIV) infection. We reviewed trials of interventions to prevent sexual transmission of any STI, employing a multilevel perspective.

METHODS

We searched MEDLINE, the Cochrane Central Register of Controlled Trials, and recent unpublished presentations through 2003, to identify randomized controlled trials of preventive STI interventions having systematic, objective measurement of STI outcomes. We classified trials according to intervention target and level of randomization (individual, group, or community); impact target (acquisition, transmission, or complications of STI); and primary intervention modality.

RESULTS

Of 83 trials identified, 41 met inclusion criteria, including trials of 28 individual-level, 9 group-level, and 4 community-level interventions. Among individual- and group-level interventions, 32 targeted acquisition, 4 targeted transmission, and 1 targeted complications of STI. The 4 intervention modalities most often used included behavior change (12 studies), vaccination (7 studies), use of topical microbicides (10 studies), and prophylactic, curative, or suppressive therapy (10 studies). Community-level interventions had multiple impact targets, and 2 interventions used multiple modalities. Only 1 intervention showed efficacy against sexual transmission of HIV, but 22 (53.7%) showed effectiveness against other STIs.

CONCLUSION

Although many interventions have been found to be effective against STIs, few have been replicated, widely implemented, or carefully evaluated for effectiveness in other settings.