Distinct HIV discordancy patterns by epidemic size in stable sexual partnerships in sub-Saharan Africa

Internalized stigma, social distance, and disclosure of HIV seropositivity in rural Uganda

BACKGROUND

HIV is highly stigmatized, compromising both treatment and prevention in resource-limited settings.

PURPOSE

We sought to study the relationship between internalized HIV-related stigma and serostatus disclosure and to determine the extent to which this association varies with the degree of social distance.

METHODS

We fit multivariable Poisson regression models, with cluster-correlated robust estimates of variance, to data from 259 persons with HIV enrolled in an ongoing cohort study in rural Uganda.

RESULTS

Persons with more internalized stigma were less likely to disclose their seropositivity. The magnitude of association increased with social distance such that the largest association was observed for public disclosures and the smallest association was observed for disclosures to sexual partners.

CONCLUSIONS

Among persons with HIV in rural Uganda, internalized stigma was negatively associated with serostatus disclosure. The inhibiting effect of stigma was greatest for the most socially distant ties.

HIV treatment-as-prevention research at a crossroads

In light of changing WHO guidelines for HIV treatment, Till Bärnighausen and colleagues consider how large-scale HIV treatment-as-prevention trials can be adapted so that they can remain viable. Please see later in the article for the Editors' Summary

The rise and fall of HIV in high-prevalence countries: a challenge for mathematical modeling

Several countries with generalized, high-prevalence HIV epidemics, mostly in sub-Saharan Africa, have experienced rapid declines in transmission. These HIV epidemics, often with rapid onsets, have generally been attributed to a combination of factors related to high-risk sexual behavior. The subsequent declines in these countries began prior to widespread therapy or implementation of any other major biomedical prevention. This change has been construed as evidence of behavior change, often on the basis of mathematical models, but direct evidence for behavior changes that would explain these declines is limited. Here, we look at the structure of current models and argue that the common “fixed risk per sexual contact" assumption favors the conclusion of substantial behavior changes. We argue that this assumption ignores reported non-linearities between exposure and risk. Taking this into account, we propose that some of the decline in HIV transmission may be part of the natural dynamics of the epidemic, and that several factors that have traditionally been ignored by modelers for lack of precise quantitative estimates may well hold the key to understanding epidemiologic trends.

Sources of HIV incidence among stable couples in sub-Saharan Africa

Introduction

The recent availability of efficacious prevention interventions among stable couples offers new opportunities for reducing HIV incidence in sub-Saharan Africa. Understanding the dynamics of HIV incidence among stable couples is critical to inform HIV prevention strategy across sub-Saharan Africa.

Methods

We quantified the sources of HIV incidence arising among stable couples in sub-Saharan Africa using a cohort-type mathematical model parameterized by nationally representative data. Uncertainty and sensitivity analyses were incorporated.

Results

HIV incidence arising among stable concordant HIV-negative couples contribute each year, on average, 29.4% of total HIV incidence; of those, 22.5% (range: 11.1%–39.8%) are infections acquired by one of the partners from sources external to the couple, less than 1% are infections acquired by both partners from external sources within a year and 6.8% (range: 3.6%–11.6%) are transmissions to the uninfected partner in the couple in less than a year after the other partner acquired the infection from an external source. The mean contribution of stable HIV sero-discordant couples to total HIV incidence is 30.4%, with most of those, 29.7% (range: 9.1%–47.9%), being due to HIV transmissions from the infected to the uninfected partner within the couple. The remaining incidence, 40.2% (range: 23.7%–64.6%), occurs among persons not in stable couples.

Conclusions

Close to two-thirds of total HIV incidence in sub-Saharan Africa occur among stable couples; however, only half of this incidence is attributed to HIV transmissions from the infected to the uninfected partner in the couple. The remaining incidence is acquired through extra-partner sex. Substantial reductions in HIV incidence can be achieved only through a prevention approach that targets all modes of HIV exposure among stable couples and among individuals not in stable couples.

HIV sexual transmission is predominantly driven by single individuals rather than discordant couples: a model-based approach

Understanding the relative contribution to HIV transmission from different social groups is important for public-health policy. Information about the importance of stable serodiscordant couples (when one partner is infected but not the other) relative to contacts outside of stable partnerships in spreading disease can aid in designing and targeting interventions. However, the overall importance of within-couple transmission, and the determinants and correlates of this importance, are not well understood. Here, we explore how mechanistic factors – like partnership dynamics and rates of extra-couple transmission – affect various routes of transmission, using a compartmental model with parameters based on estimates from Sub-Saharan Africa. Under our assumptions, when sampling model parameters within a realistic range, we find that infection of uncoupled individuals is usually the predominant route (median 0.62, 2.5%–97.5% quantiles: 0.26–0.88), while transmission within discordant couples is usually important, but rarely represents the majority of transmissions (median 0.33, 2.5%–97.5% quantiles: 0.10–0.67). We find a strong correlation between long-term HIV prevalence and the contact rate of uncoupled individuals, implying that this rate may be a key driver of HIV prevalence. For a given level of prevalence, we find a negative correlation between the proportion of discordant couples and the within-couple transmission rate, indicating that low discordance in a population may reflect a relatively high rate of within-couple transmission. Transmission within or outside couples and among uncoupled individuals are all likely to be important in sustaining heterosexual HIV transmission in Sub-Saharan Africa. Hence, intervention policies should be broadly targeted when practical.

The risk of HIV transmission within HIV-1 sero-discordant couples appears to vary across sub-Saharan Africa

BACKGROUND

Representative and precise estimates for the annual risk of HIV transmission (ϕ) from the infected to the uninfected partner in a stable HIV-1 sero-discordant couple (SDC) are not available. Nevertheless, quantifying HIV infectiousness is critical to understanding HIV epidemiology and implementing prevention programs.

MATERIALS AND METHODS

We estimated ϕ and examined its variation across 23 countries in sub-Saharan Africa (SSA) by constructing and analyzing a mathematical model that describes HIV dynamics among SDCs. The model was parameterized using empirical measures such as those of the nationally representative Demographic and Health Surveys. Uncertainty and sensitivity analyses were conducted to assess the robustness of the findings.

RESULTS

We estimated a median ϕ of 11.1 per 100 person-years across SSA. A clustering based on HIV population prevalence was observed with a median ϕ of 7.5 per 100 person-years in low HIV prevalence countries (<5%) compared to 19.5 per 100 person-years in high prevalence countries (>5%). The association with HIV prevalence explained 67% of the variation in ϕ, and suggested an increase of 0.95 per 100 person-years in ϕ for every 1% increase in HIV prevalence.

CONCLUSIONS

Empirical measures from cohort studies appear to underestimate HIV infectiousness in SSA. The risk of HIV transmission among SDCs appears also to vary across SSA, and this may have contributed to the contrasting HIV epidemic trajectories in this continent.

Can the UNAIDS modes of transmission model be improved? A comparison of the original and revised model projections using data from a setting in west Africa

Objective:

The UNAIDS modes of transmission model (MoT) is a user-friendly model, developed to predict the distribution of new HIV infections among different subgroups. The model has been used in 29 countries to guide interventions. However, there is the risk that the simplifications inherent in the MoT produce misleading findings. Using input data from Nigeria, we compare projections from the MoT with those from a revised model that incorporates additional heterogeneity.

Methods:

We revised the MoT to explicitly incorporate brothel and street-based sex-work, transactional sex, and HIV-discordant couples. Both models were parameterized using behavioural and epidemiological data from Cross River State, Nigeria. Model projections were compared, and the robustness of the revised model projections to different model assumptions, was investigated.

Results:

The original MoT predicts 21% of new infections occur in most-at-risk-populations (MARPs), compared with 45% (40–75%, 95% Crl) once additional heterogeneity and updated parameterization is incorporated. Discordant couples, a subgroup previously not explicitly modelled, are predicted to contribute a third of new HIV infections. In addition, the new findings suggest that women engaging in transactional sex may be an important but previously less recognized risk group, with 16% of infections occurring in this subgroup.

Conclusion:

The MoT is an accessible model that can inform intervention priorities. However, the current model may be potentially misleading, with our comparisons in Nigeria suggesting that the model lacks resolution, making it challenging for the user to correctly interpret the nature of the epidemic. Our findings highlight the need for a formal review of the MoT.

Preconception care for people living with HIV: recommendations for advancing implementation

Globally, research has documented high fertility desires and intentions among HIV-positive women. Improving implementation of preconception care (PCC) for people living with HIV is critical, given estimates that the majority of HIV-positive women who want future biological children have not received reproductive counseling, largely due to a lack of provider-initiated conversations. This article offers initial recommendations and outlines key considerations for a research agenda to advance PCC implementation efforts in both high-resource and low-resource settings. We consider who should provide PCC; where it can be effectively delivered; when it should be offered; and two potential implementation models depending on available resources. We conclude with a call for PCC-specific implementation science and research translation to help people living with HIV achieve their reproductive goals.

Integration of family planning services into HIV care and treatment in Kenya: a cluster-randomized trial

OBJECTIVE

To determine whether integrating family planning services into HIV care is associated with increased use of more effective contraceptive methods (sterilization, intrauterine device, implant, injectable or oral contraceptives).

DESIGN

Cluster-randomized trial.

SETTING

Eighteen public HIV clinics in Nyanza Province, Kenya.

PARTICIPANTS

Women aged 18-45 years receiving care at participating HIV clinics; 5682 clinical encounters from baseline period (December 2009-February 2010) and 12,531 encounters from end-line period (July 2011-September 2011, 1 year after site training).

INTERVENTION

Twelve sites were randomized to integrate family planning services into the HIV clinic, whereas six clinics were controls where clients desiring contraception were referred to family planning clinics at the same facility.

MAIN OUTCOME MEASURES

Increase in use of more effective contraceptive methods between baseline and end-line periods. Pregnancy rates during the follow-up year (October 2010-September 2011) were also compared.

RESULTS

Women seen at integrated sites were significantly more likely to use more effective contraceptive methods at the end of the study [increased from 16.7 to 36.6% at integrated sites, compared to increase from 21.1 to 29.8% at controls; odds ratio (OR) 1.81, 95% confidence interval (CI) 1.24-2.63]. Condom use decreased non-significantly at intervention sites compared to controls (OR 0.64, 95% CI 0.35-1.19). No difference was observed in incident pregnancy in the first year after integration comparing intervention to control sites (incidence rate ratio 0.90; 95% CI 0.68-1.20).

CONCLUSIONS

Integration of family planning services into HIV care clinics increased use of more effective contraceptive methods with a non-significant reduction in condom use. Although no significant reduction in pregnancy incidence was observed during the study, 1 year may be too short a period of observation for this outcome.

An empiric risk scoring tool for identifying high-risk heterosexual HIV-1-serodiscordant couples for targeted HIV-1 prevention

BACKGROUND AND OBJECTIVES

Heterosexual HIV-1-serodiscordant couples are increasingly recognized as an important source of new HIV-1 infections in sub-Saharan Africa. A simple risk assessment tool could be useful for identifying couples at highest risk for HIV-1 transmission.

METHODS

Using data from 3 prospective studies of HIV-1-serodiscordant couples from 7 African countries and standard methods for development of clinical prediction rules, the authors derived and validated a risk scoring tool developed from multivariate modeling and composed of key predictors for HIV-1 risk that could be measured in standard research and clinical settings.

RESULTS

The final risk score included age of the HIV-1-uninfected partner, married and/or cohabiting partnership, number of children, unprotected sex, uncircumcised male HIV-1-uninfected partner, and plasma HIV-1 RNA in the HIV-1-infected partner. The maximum risk score was 12, scores ≥5 were associated with an annual HIV-1 incidence of >3%, and couples with a score ≥6 accounted for only 28% of the population but 67% of HIV-1 transmissions. The area under the curve for predictive ability of the score was 0.74 (95% confidence interval: 0.70 to 0.78). Internal and external validation showed similar predictive ability of the risk score, even when plasma viral load was excluded from the risk score.

CONCLUSIONS

A discrete combination of clinical and behavioral characteristics defines highest risk HIV-1-serodiscordant couples. Discriminating highest risk couples for HIV-1 prevention programs and clinical trials using a validated risk score could improve research efficiency and maximize the impact of prevention strategies for reducing HIV-1 transmission.

Disclosure, knowledge of partner status, and condom use among HIV-positive patients attending clinical care in Tanzania, Kenya, and Namibia

We describe the frequency of and factors associated with disclosure, knowledge of partner's HIV status, and consistent condom use among 3538 HIV-positive patients attending eighteen HIV care and treatment clinics in Kenya, Namibia, and Tanzania. Overall, 42% of patients were male, and 64% were on antiretroviral treatment. The majority (80%) had disclosed their HIV status to their partners, 64% knew their partner's HIV status, and 77% reported consistent condom use. Of those who knew their partner's status, 18% reported their partner was HIV negative. Compared to men, women were significantly less likely to report disclosing their HIV status to their sex partner(s), to knowing their partner's HIV status, and to using condoms consistently with HIV-negative partners. Other factors negatively associated with consistent condom use include nondisclosure, alcohol use, reporting a casual sex partner, and desiring a pregnancy. Health care providers should target additional risk reduction counseling and support services to patients who report these characteristics.

Maximizing the impact of HIV prevention efforts: interventions for couples

Despite efforts to increase access to HIV testing and counseling services, population coverage remains low. As a result, many people in sub-Saharan Africa do not know their own HIV status or the status of their sex partner(s). Recent evidence, however, indicates that as many as half of HIV-positive individuals in ongoing sexual relationships have an HIV-negative partner and that a significant proportion of new HIV infections in generalized epidemics occur within serodiscordant couples. Integrating couples HIV testing and counseling (CHTC) into routine clinic- and community-based services can significantly increase the number of couples where the status of both partners is known. Offering couples a set of evidence-based interventions once their HIV status has been determined can significantly reduce HIV incidence within couples and if implemented with sufficient scale and coverage, potentially reduce population-level HIV incidence as well. This article describes these interventions and their potential benefits.

Extra-couple HIV transmission in sub-Saharan Africa: a mathematical modelling study of survey data

BACKGROUND

The proportion of heterosexual HIV transmission in sub-Saharan Africa that occurs within cohabiting partnerships, compared with that in single people or extra-couple relationships, is widely debated. We estimated the proportional contribution of different routes of transmission to new HIV infections. As plans to use antiretroviral drugs as a strategy for population-level prevention progress, understanding the importance of different transmission routes is crucial to target intervention efforts.

METHODS

We built a mechanistic model of HIV transmission with data from Demographic and Health Surveys (DHS) for 2003-2011, of 27,201 cohabiting couples (men aged 15-59 years and women aged 15-49 years) from 18 sub-Saharan African countries with information about relationship duration, age at sexual debut, and HIV serostatus. We combined this model with estimates of HIV survival times and country-specific estimates of HIV prevalence and coverage of antiretroviral therapy (ART). We then estimated the proportion of recorded infections in surveyed cohabiting couples that occurred before couple formation, between couple members, and because of extra-couple intercourse.

FINDINGS

In surveyed couples, we estimated that extra-couple transmission accounted for 27-61% of all HIV infections in men and 21-51% of all those in women, with ranges showing intercountry variation. We estimated that in 2011, extra-couple transmission accounted for 32-65% of new incident HIV infections in men in cohabiting couples, and 10-47% of new infections in women in such couples. Our findings suggest that transmission within couples occurs largely from men to women; however, the latter sex have a very high-risk period before couple formation.

INTERPRETATION

Because of the large contribution of extra-couple transmission to new HIV infections, interventions for HIV prevention should target the general sexually active population and not only serodiscordant couples.

FUNDING

US National Institutes of Health, US National Science Foundation, and J S McDonnell Foundation.

Considerations regarding antiretroviral chemoprophylaxis and heterosexuals in generalized epidemic settings

PURPOSE OF REVIEW

To discuss the factors pertinent to the use of pre-exposure prophylaxis (PrEP) by at-risk heterosexuals in countries with generalized HIV epidemics.

RECENT FINDINGS

PrEP will have the greatest prevention effect if targeted to those at highest risk, but identifying and engaging such persons is challenging. Serodiscordant couples account for a high proportion of new infections and are an appropriate target for PrEP, but the proportion of people in such relationships is small and outside partnerships are common. Differences in adherence coupled to pharmacology of the drugs may account for differences in efficacy seen in the trials. Mathematical modeling indicates that the benefits of PrEP in highly endemic settings outweigh the risk of induced viral resistance. Behavioral risk compensation was not observed in the trials, but current open-label studies will better determine if disinhibition will be an important problem.

CONCLUSIONS

PrEP is a potentially useful HIV-prevention strategy for generalized heterosexual epidemics. Optimal implementation will require learning more about ways to improve acceptability and adherence and how best to deliver PrEP within the context of limited resource availability.

HIV prevention in care and treatment settings: baseline risk behaviors among HIV patients in Kenya, Namibia, and Tanzania

HIV care and treatment settings provide an opportunity to reach people living with HIV/AIDS (PLHIV) with prevention messages and services. Population-based surveys in sub-Saharan Africa have identified HIV risk behaviors among PLHIV, yet data are limited regarding HIV risk behaviors of PLHIV in clinical care. This paper describes the baseline sociodemographic, HIV transmission risk behaviors, and clinical data of a study evaluating an HIV prevention intervention package for HIV care and treatment clinics in Africa. The study was a longitudinal group-randomized trial in 9 intervention clinics and 9 comparison clinics in Kenya, Namibia, and Tanzania (N = 3538). Baseline participants were mostly female, married, had less than a primary education, and were relatively recently diagnosed with HIV. Fifty-two percent of participants had a partner of negative or unknown status, 24% were not using condoms consistently, and 11% reported STI symptoms in the last 6 months. There were differences in demographic and HIV transmission risk variables by country, indicating the need to consider local context in designing studies and using caution when generalizing findings across African countries. Baseline data from this study indicate that participants were often engaging in HIV transmission risk behaviors, which supports the need for prevention with PLHIV (PwP).

Only a fraction of new HIV infections occur within identifiable stable discordant couples in sub-Saharan Africa

OBJECTIVE

To estimate the contribution of HIV-1 sero-conversions among stable HIV sero-discordant couples (SDCs) to total HIV population-level incidence in sub-Saharan Africa.

DESIGN AND METHODS

We constructed a mathematical model, grounded in nationally representative demographic and epidemiological data, that estimates the annual number of HIV-1 transmissions from the infected partners to the uninfected partners among established SDCs, and compares its value to an estimate for the overall HIV population-level incidence in 20 countries in sub-Saharan Africa. We defined identifiable HIV-1 transmissions among SDCs as those that a hypothetical screening and intervention program would have the potential to avert. Uncertainty and sensitivity analyses were incorporated to assess the robustness of the findings.

RESULTS

Across the 20 countries, an average of 29% (range: 10-52%) of new HIV-1 infections occurred in which one partner in an identifiable SDC infected the other. The percentage of total HIV new infections in a country that occurred within such identifiable SDCs tended to be lower in countries with larger general population HIV epidemics. For most countries, HIV-1 incidence among SDCs is unlikely to exceed 50% of new HIV infections in the whole population.

CONCLUSION

Only a fraction of HIV-1 heterosexual transmissions occur within identifiable SDCs. Prevention within SDCs at scale requires a series of potentially challenging programmatic requirements to be met. Despite the importance of prevention programs aiming at protecting the sero-negative partner in an SDC, a wider strategy utilizing the full range of prevention modalities, which would limit the original generation of SDCs, is also needed.

Antiretroviral-based HIV-1 prevention: antiretroviral treatment and pre-exposure prophylaxis

Antiretroviral-based HIV-1 prevention strategies - including antiretroviral treatment (ART) to reduce the infectiousness of individuals with HIV-1 and oral and topical pre-exposure prophylaxis (PrEP) for uninfected individuals to prevent HIV-1 acquisition - are the most promising new approaches for decreasing HIV-1 spread. Observational studies among HIV-1 serodiscordant couples have associated ART initiation with a reduction in HIV-1 transmission risk of 80-92%, and a recent randomized trial demonstrated that earlier initiation of ART (that is, at CD4(+) T-cell counts between 350 and 550 cells/mm(3)), in the context of virological monitoring and adherence support, resulted in a 96% reduction in HIV-1 transmission. A number of ongoing and recently-completed clinical trials have assessed the efficacy of PrEP for HIV-1 prevention as pericoitally administered or daily-administered 1% tenofovir gel and daily oral tenofovir disoproxil fumarate (TDF) and combination emtricitabine (FTC)/TDF. Completed studies have demonstrated HIV-1 protection efficacies ranging from 39% to 75%. However, two trials in African women have shown no HIV-1 protection with TDF and FTC/TDF PrEP; the reasons for lack of efficacy in those trials are being investigated. Adherence is likely the key to efficacy of antiretrovirals for HIV-1 prevention, both as ART and PrEP. Critical unanswered questions for successful delivery of antiretroviral-based HIV-1 prevention include how to target ART and PrEP to realize maximum population benefits, whether HIV-1-infected individuals at earlier stages of infection would accept ART to reduce their risk for transmitting HIV-1 and whether highest-risk HIV-1-negative persons would use PrEP, and whether high adherence could be sustained to achieve high effectiveness.

HIV treatment as prevention: optimising the impact of expanded HIV treatment programmes

Until now, decisions about how to allocate ART have largely been based on maximising the therapeutic benefit of ART for patients. Since the results of the HPTN 052 study showed efficacy of antiretroviral therapy (ART) in preventing HIV transmission, there has been increased interest in the benefits of ART not only as treatment, but also in prevention. Resources for expanding ART in the short term may be limited, so the question is how to generate the most prevention benefit from realistic potential increases in the availability of ART. Although not a formal systematic review, here we review different ways in which access to ART could be expanded by prioritising access to particular groups based on clinical or behavioural factors. For each group we consider (i) the clinical and epidemiological benefits, (ii) the potential feasibility, acceptability, and equity, and (iii) the affordability and cost-effectiveness of prioritising ART access for that group. In re-evaluating the allocation of ART in light of the new data about ART preventing transmission, the goal should be to create policies that maximise epidemiological and clinical benefit while still being feasible, affordable, acceptable, and equitable.

Optimal uses of antiretrovirals for prevention in HIV-1 serodiscordant heterosexual couples in South Africa: a modelling study

BACKGROUND

Antiretrovirals have substantial promise for HIV-1 prevention, either as antiretroviral treatment (ART) for HIV-1-infected persons to reduce infectiousness, or as pre-exposure prophylaxis (PrEP) for HIV-1-uninfected persons to reduce the possibility of infection with HIV-1. HIV-1 serodiscordant couples in long-term partnerships (one member is infected and the other is uninfected) are a priority for prevention interventions. Earlier ART and PrEP might both reduce HIV-1 transmission in this group, but the merits and synergies of these different approaches have not been analyzed.

METHODS AND FINDINGS

We constructed a mathematical model to examine the impact and cost-effectiveness of different strategies, including earlier initiation of ART and/or PrEP, for HIV-1 prevention for serodiscordant couples. Although the cost of PrEP is high, the cost per infection averted is significantly offset by future savings in lifelong treatment, especially among couples with multiple partners, low condom use, and a high risk of transmission. In some situations, highly effective PrEP could be cost-saving overall. To keep couples alive and without a new infection, providing PrEP to the uninfected partner could be at least as cost-effective as initiating ART earlier in the infected partner, if the annual cost of PrEP is <40% of the annual cost of ART and PrEP is >70% effective.

CONCLUSIONS

Strategic use of PrEP and ART could substantially and cost-effectively reduce HIV-1 transmission in HIV-1 serodiscordant couples. New and forthcoming data on the efficacy of PrEP, the cost of delivery of ART and PrEP, and couples behaviours and preferences will be critical for optimizing the use of antiretrovirals for HIV-1 prevention. Please see later in the article for the Editors' Summary.