Universal access to HIV treatment versus universal 'test and treat': transmission, drug resistance & treatment costs

Promoting HIV care continuum outcomes among people who use drugs and alcohol: a systematic review of randomized trials evaluating behavioral HIV care interventions published from 2011 to 2023

BACKGROUND

Substance use remains a robust predictor of HIV infection and a serious impediment to HIV care continuum progression for people living with HIV. The primary research question of this systematic review is focused on understanding the extent to which behavioral HIV care interventions have been efficacious in helping people who live with HIV and who use substances along the HIV care continuum.

METHODS

Using PubMed and ProQuest databases, we performed a systematic review of randomized trials of behavioral HIV care continuum interventions among people who use substances published from 2011 to August 2023, since the beginning of the treatment-as-prevention era.

RESULTS

We identified 11 studies (total participants: N = 5635), ten intentionally targeting substance-using populations. Four studies involved samples using ≥ 1 substance (e.g., alcohol, opioids, stimulants, marijuana); four involved injection drug use; one involved methamphetamine use; and one involved alcohol use. One study targeted a population with incidental substance use (i.e., alcohol, injection drug use, non-injection drug use reported in most participants). Each study defined one or more HIV care outcomes of interest. Viral suppression was an outcome targeted in 9/11 studies, followed by uptake of antiretroviral therapy (ART; 7/11), ART adherence (6/11), retention in care (5/11), and linkage to care (3/11). While most (nine) of the studies found significant effects on at least one HIV care outcome, findings were mostly mixed. Mediated (2/11) and moderated (2/11) effects were minimally examined.

CONCLUSIONS

The results from this systematic review demonstrate mixed findings concerning the efficacy of previous HIV care interventions to improve HIV care continuum outcomes among people who use substances. However, heterogeneity of study components (e.g., diversity of substances used/assessed, self-report vs. objective measures, attrition) prevent broad deductions or conclusions about the amenability of specific substance-using populations to HIV care intervention. More coordinated, comprehensive, and targeted efforts are needed to promote and disentangle intervention effects on HIV care continuum outcomes among substance-using populations.

The Impact of Universal Test and Treat Program on Highly Active Anti Retroviral Therapy Outcomes (Coverage, Adherence and Lost to Follow Up) at Wangaya Hospital in Denpasar, Bali-Indonesia: A Retrospective Cohort Study

Background:

World Health Organization (WHO) (2015) recommended that all people diagnosed with human immunodeficiency virus (HIV)-positive initiate Highly Active Anti Retroviral Therapy (HAART) immediately (less than a week), irrespective of CD4 count (Universal Test and Treat / UTT) Program.

Objective:

To evaluate the impact of UTT as a current therapeutic program on HIV treatment outcomes, coverage, adherence, and lost to follow-up (LTFU) at Wangaya Hospital in Denpasar, Bali, Indonesia.

Methods:

A Retrospective cohort study was conducted during July 2017 - June 2018 (Pre-UTT) and September 2018 – August 2019 (Post-UTT). Around 402 medical records were selected, reviewed, and enrolled. Data were analyzed using SPSS software for windows version 24.0. Bivariate analysis (Chi-square test) was performed on all variables with a statistically significant t level of 0.05.

Results:

Among 4,322 new visitors; 3,585 (82.95%) agreed to take HIV test and 402(11.21%) were confirmed HIV reactive. Most participants confirmed HIV reactive occured at age 25-34 years old and 230 (57.21%) were male. The majority education level were primary (Junior high school) 302(75.12%), 379(94.28%) were employed and 281 (69.90%) stayed in Denpasar. About 350 (87.06%) received HAART, 298 (85.14%) with high adherence and 52 (14.86%) LTFU. Pre-UTT, HAART coverage; 83.03% (181), were statistically significant increased to 91.85% (169) post UTT (p=0.000). High adherence pre-UTT; 79.56% (144) was significantly increased to 91.12% (154) post UTT (p=0.006) and LTFU were significantly decreased; 20.44% (37) to 8.87% (15) (p=0.006).

Conclusion:

UTT program significantly improve the HIV treatment outcome (increased coverage, adherence, and decreased LTFU).

Using repeated home-based HIV testing services to reach and diagnose HIV infection among persons who have never tested for HIV, Chókwè health demographic surveillance system, Chókwè district, Mozambique, 2014-2017

Background

HIV prevalence in Mozambique (12.6%) is one of the highest in the world, yet ~40% of people living with HIV (PLHIV) do not know their HIV status. Strategies to increase HIV testing uptake and diagnosis among PLHIV are urgently needed. Home-based HIV testing services (HBHTS) have been evaluated primarily as a 1-time campaign strategy. Little is known about the potential of repeating HBHTS to diagnose HIV infection among persons who have never been tested (NTs), nor about factors/reasons associated with never testing in a generalized epidemic setting.

Methods

During 2014–2017, counselors visited all households annually in the Chókwè Health and Demographic Surveillance System (CHDSS) and offered HBHTS. Cross-sectional surveys were administered to randomly selected 10% or 20% samples of CHDSS households with participants aged 15–59 years before HBHTS were conducted during the visit. Descriptive statistics and logistic regression were used to assess the proportion of NTs, factors/reasons associated with never having been tested, HBHTS acceptance, and HIV-positive diagnosis among NTs.

Results

The proportion of NTs decreased from 25% (95% confidence interval [CI]:23%–26%) during 2014 to 12% (95% CI:11% –13%), 7% (95% CI:6%–8%), and 7% (95% CI:6%–8%) during 2015, 2016, and 2017, respectively. Adolescent boys and girls and adult men were more likely than adult women to be NTs. In each of the four years, the majority of NTs (87%–90%) accepted HBHTS. HIV-positive yield among NTs subsequently accepting HBHTS was highest (13%, 95% CI:10%–15%) during 2014 and gradually reduced to 11% (95% CI:8%–15%), 9% (95% CI:6%–12%), and 2% (95% CI:0%–4%) during 2015, 2016, and 2017, respectively.

Conclusions

Repeated HBHTS was helpful in increasing HIV testing coverage and identifying PLHIV in Chókwè. In high HIV-prevalence settings with low testing coverage, repeated HBHTS can be considered to increase HIV testing uptake and diagnosis among NTs.

A community-based HIV counselling and testing programme found a decreasing proportion of new HIV testers in South Africa

This article assesses the history of HIV testing among community-based HIV counselling and testing (CBCT) clients between 2014 and 2018 in 13 South African districts. Consenting clients were tested for HIV and interviewed to categorise as first-time testers or repeat testers. Of the 1 800 753 clients tested for HIV, 15.7% (95% CI [15.6-15.7]) were first-time testers. The rate of identifying first-time testers decreased by 10.7% in four years from 18.4% in year one to 7.7% in year four. A substantial proportion (5.5% [5.4-5.6]) of HIV-positive people not yet on antiretroviral treatment sought HIV re-test, of whom nearly half (48.4% [47.1-49.6]) did not disclose their HIV-positive status during pre-counselling and were re-tested. A decreasing proportion of first-time testers may signal positive progress towards universal HIV testing. This downward trend should be sustained to control the HIV epidemic.

Rapid Initiation of Antiretroviral Therapy Following Diagnosis of Human Immunodeficiency Virus Among Patients with Commercial Insurance Coverage

BACKGROUND

New guidelines for the treatment of human immunodeficiency virus (HIV) advocate for rapid initiation of antiretroviral therapy (ART) ≤ 7 days after HIV diagnosis with agents that have a high genetic barrier to resistance, good tolerability, and convenient dosing.

OBJECTIVE

To describe characteristics, time to ART initiation, and health care costs in commercially insured patients living with HIV in the United States who are treated ≤ 60 days after HIV diagnosis.

METHODS

IBM MarketScan Research Databases (January 1, 2012-December 31, 2017) were used to identify ART-naive adults with HIV-1, ≥ 6 months of continuous eligibility before first HIV diagnosis, and ART initiation ≤ 60 days of first diagnosis. ART regimen had to include a protease inhibitor (PI), an integrase strand transfer inhibitor (INSTI), or a non-nucleoside reverse transcriptase inhibitor (NNRTI) with ≥ 2 nucleoside reverse transcriptase inhibitors. Cohorts were formed based on time to ART initiation after diagnosis: ≤ 7 days or 8-60 days. Health care costs were evaluated at 6, 12, 24, and 36 months after diagnosis among patients with ≥ 36 months of continuous eligibility.

RESULTS

Among 9,351 patients, median time to treatment was 31.0 days. Patients initiating ART > 60 days after HIV diagnosis were excluded (N = 2,608 [27.9%]), while 6,743 (72.1%) initiated ART ≤ 60 days after diagnosis and were analyzed; 18.3% and 81.7% were classified in the ≤ 7 days and 8-60 days cohorts, respectively. For all analyzed patients, mean age was 38.0 (SD = 12.0) years and 13.2% were female; 12.7%, 56.2%, and 31.1% initiated a PI, INSTI, or NNRTI-based regimen, respectively. Elvitegravir (32.9%), efavirenz (20.9%), dolutegravir (18.5%), and darunavir (8.5%) were the most commonly used antiretrovirals; most patients (74.3%) were initiated on single-tablet regimens. PI-based regimens were more common in the ≤ 7 days cohort (PI = 18.1%; darunavir = 11.4%) than in the 8-60 days cohort (PI = 11.5%; darunavir = 7.8%). INSTI-based regimens were more common in the 8-60 days cohort (INSTI = 57.7%; elvitegravir = 33.8%) than in the ≤ 7 days cohort (INSTI = 49.2%; elvitegravir = 29.1%). NNRTI-based regimens were as common in the ≤ 7 days (32.7%) and 8-60 days (30.7%) cohorts. Mean total accumulated costs were lower among patients in the ≤ 7 days cohort than in the 8-60 days cohort at all time points analyzed after diagnosis (e.g., 36 months: ≤ 7 days = $109,456; 8-60 days = $116,870). Total per-patient per-month costs decreased over time in the ≤ 7 days (i.e., 6 months = $4,359; 36 months = $3,040) and 8-60 days cohort (6 months = $4,727; 36 months = $3,246).

CONCLUSIONS

Although 72.1% of patients initiated ART ≤ 60 days after HIV diagnosis, only 18.3% initiated ART ≤ 7 days. Many patients initiating ART ≤ 7 days used suboptimal agents with low rather than high genetic barriers to resistance (i.e., efavirenz and elvitegravir) or agents (dolutegravir) coformulated with other antiretrovirals that require testing to prevent hypersensitivity reactions. Patients in the ≤ 7 days cohort showed lower total health care costs relative to those in the 8-60 days cohort, highlighting the potential long-term benefits of rapid ART initiation.

DISCLOSURES

This study was supported by Janssen Scientific Affairs, which was involved in the study design, interpretation of results, manuscript preparation, and publication decisions. Emond, Lefebvre, Lafeuille, and Côté-Sergent are employees of Analysis Group, a consulting company that was contracted by Janssen Scientific Affairs to conduct this study and develop the manuscript. Benson, Tandon, Chow, and Dunn are employees of Janssen Scientific Affairs and stockholders of Johnson & Johnson. Part of the material in this study has been presented at the AMCP 2019 Annual Meeting; March 25-28, 2019; San Diego, CA.

The costs of home-based HIV testing and counselling in sub-Saharan Africa and its association with testing yield: a literature review

More than 14.5 of the 36.7 million people living with HIV globally do not know their HIV status, making comprehensive testing interventions a critical step in ending the HIV/AIDS epidemic. Home-based testing and counselling (HBTC) involves small teams of community health workers with basic training going from door-to-door and offering services in people's homes. HBTC is effective in reaching individuals that are unlikely to test otherwise, but there is conflicting evidence on its costs and little insight into why estimates are different. We undertook a comparative review of existing costing studies of HBTC in sub-Saharan Africa. Yield or positivity rate, the number of persons tested positive among all tested, is an important metric to judge the efficacy of a testing campaign. We conducted descriptive analyses to test whether unit costs are associated with yield. Studies varied in size with a maximum of 264 953 and a minimum of 494 persons tested. The average "cost per person tested" across 14 studies was $22.8 (SD $14.5) with a minimum of $6 and a maximum of $55.4, and the average "cost per person tested HIV-positive' across 12 studies was $439.4 (SD $399.7) with a minimum of $66.2 and a maximum of $800.9. Correlations between unit cost estimates and yield were not statistically significant. Existant estimates of the costs of HBTC are conflicting, and it is likely that differences in the setting, design and implementation of the studies are responsible for the discrepancies. This makes it difficult to reliably estimate the costs and cost-effectiveness of HBTC.

Drug resistance from preferred antiretroviral regimens for HIV infection in South Africa: A modeling study

BACKGROUND

Tenofovir-containing regimens comprise the preferred first-line antiretroviral therapy (ART) in many countries including South Africa, where utilization of second-line regimens is limited. Considerable HIV drug resistance has occurred among persons failing tenofovir-containing first-line ART. We evaluated drug resistance at the population level using mathematical modeling.

SETTING

Heterosexual HIV epidemic in KwaZulu-Natal, South Africa.

METHODS

We constructed a stochastic individual-based model and simulated scenarios of ART implementation, either CD4-based (threshold < 500 cells/mL) or Fast-track (81% coverage by 2020), with consideration of major drug-associated mutations (M184V, K65R and non-nucleoside reverse transcriptase inhibitor (NNRTI)). Using base case and uncertainty analyses, we assessed (majority) drug resistance levels.

RESULTS

By 2030, the median total resistance (proportion of HIV-infected persons with drug resistance) is predicted to reach 31.4% (interquartile range (IQR): 16.5%-50.2%) with CD4-based ART, decreasing to 14.5% (IQR: 7.7%-25.8%) with Fast-track implementation. In both scenarios, we find comparably high prevalence (~80%) of acquired NNRTI-associated, M184V and K65R mutations. Over 48% of individuals with acquired resistance harbor dual, 44% triple and 7% just single drug mutations. Drug-resistant HIV is predicted to comprise 40% (IQR: 27%-50%) of incident infections, while 70% of prevalent transmitted resistance is NNRTI-associated. At 2018, the projected total resistance is 15% (IQR: 7.5%-25%), with 18% (IQR: 13%-24%) of incident infections from transmitted drug-resistant HIV.

CONCLUSIONS

WHO-recommended preferred first-line ART could lead to substantial drug resistance. Effective surveillance of HIV drug resistance and utilization of second-line as well as alternative first-line regimens is crucial.

"Is it making any difference?" A qualitative study examining the treatment-taking experiences of asymptomatic people living with HIV in the context of Treat-all in Eswatini

INTRODUCTION

Treat-all is being implemented in several African settings, in accordance with 2015 World Health Organisation guidelines. The factors known to undermine adherence to antiretroviral therapy (ART) may change in the context of Treat-all, where people living with HIV (PLHIV) increasingly initiate ART at earlier, asymptomatic stages of disease, soon after diagnosis. This paper aimed to examine the asymptomatic PLHIV's experiences engaging with early ART initiation under the Treat-all policy, including how they navigate treatment-taking over the longer term.

METHODS

A longitudinal qualitative study was conducted within a Médecins Sans Frontières/Ministry of Health Treat-all pilot in Shiselweni, southern Eswatini. The Treat-all pilot began in October 2014, adopted into national policy in October 2016. Participants were recruited purposively to include newly diagnosed, clinically asymptomatic PLHIV with a range of treatment-taking experiences, and healthcare workers (HCW) with various roles. This analysis drew upon a sub-sample of 17 PLHIV who had been on ART for at least 12 months, with mean 20 months on ART at first interview, and who undertook three interviews each. Additionally, 20 HCWs were interviewed once. Interviews were conducted from August 2016 to September 2017. Data were analysed thematically using coding, drawing upon principles of grounded theory, and aided by Nvivo 11.

RESULTS

It was important for PLHIV to perceive the need for treatment, and to have evidence of its effectiveness to motivate their treatment-taking, thereby supporting engagement with care. For some, coming to terms with a HIV diagnosis or re-interpreting past illnesses as signs of HIV could point to the need for ART to prevent health deterioration and prolong life. However, others doubted the accuracy of an HIV diagnosis and the need for treatment in the absence of symptoms or signs of ill health, with some experimenting with treatment-taking as a means of seeking evidence of their need for treatment and its effect. Viral load monitoring appeared important in offering a view of the effect of treatment on the level of the virus, thereby motivating continued treatment-taking.

CONCLUSIONS

These findings highlight the importance of PLHIV perceiving need for treatment and having evidence of the difference that ART is making to them for motivating treatment-taking. Patient support should be adapted to address these concerns, and viral load monitoring made routinely available within Treat-all care, with communication of suppressed results emphasized to patients.

Mathematical modelling to inform 'treat all' implementation in sub-Saharan Africa: a scoping review

OBJECTIVE

Despite widespread uptake, only half of sub-Saharan African countries have fully implemented the World Health Organization's 'treat all' policy, hindering achievement of global HIV targets. We examined literature on mathematical modelling studies that sought to inform scale-up and implementation of 'treat all' in sub-Saharan Africa.

METHODS

We conducted a scoping review, a research synthesis to assess emerging evidence and identify gaps, of peer-reviewed literature, extracting study characteristics on 'treat all' policies and assumptions, setting, key populations, outcomes and findings. Studies were narratively summarised and potential gaps characterised.

RESULTS

We identified 16 studies examining 'treat all' alone (n=12) or with expanded testing (n=7) and/or care continuum improvements (n=6). Twelve studies examined 'treat all' for Southern African countries, while none did so for Central Africa. Four included the role of resistance; one evaluated any key population. A range of health and economic outcomes were reported, although fewer studies formally assessed budget impact. Fourteen studies involved co-authors with any in-country affiliation; one study also had co-authors with local government affiliation. Overall, 'treat all' improves health outcomes and is cost-effective compared to deferred HIV treatment; 'treat all' with expanded testing or care continuum improvements may provide further health benefits. However, studies generally used optimistic assumptions about the implementation of expanded testing or care continuum improvements.

CONCLUSIONS

The modelling literature demonstrates improved health and economic benefits of 'treat all'. Using mathematical modelling to inform real-world implementation of 'treat all' requires realistic assumptions about expanded testing and care continuum interventions across a wide range of settings and populations.

Success factors for universal access to antiretroviral treatments in South Africa

This article studies the epidemiological and economic impacts of a universal testing and treatment policy of Human Immunodeficiency Virus (HIV) in South Africa. A model of disease transmission is built to simulate several implementation scenarios of the policy. Different behavioral responses in the general population are considered. The results show that the success of a large-scale HIV testing and treatment program in South Africa depends on its implementation conditions. The policy can lead to a reduction of the HIV epidemic, even in the case of a large relapse in preventive behaviors in the general population, if implementation conditions are favorable. This is the case if the number of infected individuals who are infectious is greatly reduced. From an economic point of view, taking into account the positive externality of antiretroviral (ARV) treatments changes the traditional framework of cost-benefit analyses. A large-scale testing and treatment program would be cost-saving in the case of favorable implementation conditions, even following a large increase in risk behaviors after the scaling up of ARV treatments. By contrast, the analysis stresses out the potential perverse effects of scaling up ARV treatments in South Africa if the intervention is set up without ensuring enough resources for patients' monitoring and the availability of effective ARV drugs. Indeed, if the number of treated patients rises while adherence of patients to treatments decreases and the rate of loss to follow-up increases, the policy could extend the pool of infectious patients and lead to a long-term amplification of the epidemic.

Factors that Motivated Otherwise Healthy HIV-Positive Young Adults to Access HIV Testing and Treatment in South Africa

The World Health Organization recommends early initiation of HIV antiretroviral therapy (ART) for all those infected with the virus at any CD4 count. Successfully reaching individuals with relatively high CD4 counts depends in large part on healthy individuals seeking testing and treatment; however, little is known about factors motivating this decision. We conducted a qualitative study to explore this issue among 25 young HIV-positive adults (age 18-35) with a CD4 count >350 cells/mm³ who recently started or made the decision to start ART in Gugulethu, South Africa. Using an inductive content analytical approach, we found that most individuals sought testing and treatment early in the disease progression because of a desire to appear healthy thereby avoiding stigma associated with AIDS. Other factors included social support, responsibilities and aspirations, normalcy of having HIV, and accessible services. These findings suggest that maintenance of physical appearance should be included in the development of novel testing and treatment interventions.

Early antiretroviral therapy and potent second-line drugs could decrease HIV incidence of drug resistance

Early initiation of antiretroviral therapy (ART) reduces the risk of drug-sensitive HIV transmission but may increase the transmission of drug-resistant HIV. We used a mathematical model to estimate the long-term population-level benefits of ART and determine the scenarios under which earlier ART (treatment at 1 year post-infection, on average) could decrease simultaneously both total and drug-resistant HIV incidence (new infections). We constructed an infection-age-structured mathematical model that tracked the transmission rates over the course of infection and modelled the patients' life expectancy as a function of ART initiation timing. We fitted this model to the annual AIDS incidence and death data directly, and to resistance data and demographic data indirectly among men who have sex with men (MSM) in San Francisco. Using counterfactual scenarios, we assessed the impact on total and drug-resistant HIV incidence of ART initiation timing, frequency of acquired drug resistance, and second-line drug effectiveness (defined as the combination of resistance monitoring, biomedical drug efficacy and adherence). Earlier ART initiation could decrease the number of both total and drug-resistant HIV incidence when second-line drug effectiveness is sufficiently high (greater than 80%), but increase the proportion of new infections that are drug resistant. Thus, resistance may paradoxically appear to be increasing while actually decreasing.

The importance of choice disability and structural intervention in the HIV epidemic in Sub-Saharan Africa

Background

Despite massive investment in HIV control programs, HIV incidence rates in countries with generalized epidemics have not fallen for most of the last decade. It appears that those at risk are not adopting effective prevention strategies. Those who are unable to implement their prevention preferences are referred to as choice disabled. We examined how and to what extent structural intervention measures that support choice-disabled individuals can reduce HIV transmission and prevalence.

Methods

A mathematical model was developed to describe HIV transmission among and between choice-disabled and choice-enabled individuals. Data were available from field trials identifying factors and effects of choice disability. The model was used to estimate the potential impact of an intervention strategy in which choice-disabled individuals are enabled to make prevention choices. Several scenarios were considered and compared: supporting only one or both genders; supporting only HIV– individuals or also HIV+ choice-disabled individuals.

Results

Substantial declines in HIV incidence and prevalence are observed when supportive interventions are included in the model. The magnitude of these declines depends on the scope of the intervention program. The largest positive effect occurs when the support program is offered regardless of HIV status.

Conclusions

Addressing the effects of choice disability in any HIV intervention program could be crucial to the program’s success. Structural intervention programs to support choice-disabled individuals in implementing prevention strategies greatly reduce HIV incidence and prevalence in mathematical models.

Future technologies for monitoring HIV drug resistance and cure

PURPOSE OF REVIEW

Sensitive, scalable and affordable assays are critically needed for monitoring the success of interventions for preventing, treating and attempting to cure HIV infection. This review evaluates current and emerging technologies that are applicable for both surveillance of HIV drug resistance (HIVDR) and characterization of HIV reservoirs that persist despite antiretroviral therapy and are obstacles to curing HIV infection.

RECENT FINDINGS

Next-generation sequencing (NGS) has the potential to be adapted into high-throughput, cost-efficient approaches for HIVDR surveillance and monitoring during continued scale-up of antiretroviral therapy and rollout of preexposure prophylaxis. Similarly, improvements in PCR and NGS are resulting in higher throughput single genome sequencing to detect intact proviruses and to characterize HIV integration sites and clonal expansions of infected cells.

SUMMARY

Current population genotyping methods for resistance monitoring are high cost and low throughput. NGS, combined with simpler sample collection and storage matrices (e.g. dried blood spots), has considerable potential to broaden global surveillance and patient monitoring for HIVDR. Recent adaptions of NGS to identify integration sites of HIV in the human genome and to characterize the integrated HIV proviruses are likely to facilitate investigations of the impact of experimental 'curative' interventions on HIV reservoirs.

Dynamic Transmission Economic Evaluation of Infectious Disease Interventions in Low- and Middle-Income Countries: A Systematic Literature Review

Economic evaluation using dynamic transmission models is important for capturing the indirect effects of infectious disease interventions. We examine the use of these methods in low- and middle-income countries, where infectious diseases constitute a major burden. This review is comprised of two parts: (1) a summary of dynamic transmission economic evaluations across all disease areas published between 2011 and mid-2014 and (2) an in-depth review of mosquito-borne disease studies focusing on health economic methods and reporting. Studies were identified through a systematic search of the MEDLINE database and supplemented by reference list screening. Fifty-seven studies were eligible for inclusion in the all-disease review. The most common subject disease was HIV/AIDS, followed by malaria. A diverse range of modelling methods, outcome metrics and sensitivity analyses were used, indicating little standardisation. Seventeen studies were included in the mosquito-borne disease review. With notable exceptions, most studies did not employ economic evaluation methods beyond calculating a cost-effectiveness ratio or net benefit. Many did not adhere to health care economic evaluations reporting guidelines, particularly with respect to full model reporting and uncertainty analysis. We present a summary of the state-of-the-art and offer recommendations for improved implementation and reporting of health economic methods in this crossover discipline.

Are Interferon-Free Direct-Acting Antivirals for the Treatment of HCV Enough to Control the Epidemic among People Who Inject Drugs?

BACKGROUND

Widely access to interferon-free direct-acting antiviral regimens (IFN-free DAA) is poised to dramatically change the impact of the HCV epidemic among people who inject drugs (PWID). We evaluated the long-term effect of increasing HCV testing, treatment and engagement into harm-reduction activities, focused on active PWID, on the HCV epidemic in British Columbia (BC), Canada.

METHODS

We built a compartmental model of HCV disease transmission stratified by disease progression, transmission risk, and fibrosis level. We explored the effect of: (1) Increasing treatment rates from 8 to 20, 40 and 80 per 1000 infected PWID/year; (2) Increasing treatment eligibility based on fibrosis level; (3) Maximizing the effect of testing by performing it immediately upon ending the acute phase; (4) Increasing access to harm-reduction activities to reduce the risk of re-infection; (5) Different HCV antiviral regimens on the Control Reproduction Number Rc. We assessed the impact of these interventions on incidence, prevalence and mortality from 2016 to 2030.

RESULTS

Of all HCV antiviral regimens, only IFN-free DAAs offered a high chance of disease elimination (i.e. Rc < 1), but it would be necessary to substantially increase the current low testing and treatment rates. Assuming a treatment rate of 80 per 1000 infected PWID per year, coupled with a high testing rate, the incidence rate, at the end of 2030, could decrease from 92.9 per 1000 susceptible PWID per year (Status Quo) to 82.8 (by treating only PWID with fibrosis level F2 and higher) or to 65.5 (by treating PWID regardless of fibrosis level). If PWID also had access to increased harm-reduction activities, the incidence rate further decreased to 53.1 per 1000 susceptible PWID per year. We also obtained significant decreases in prevalence and mortality at the end of 2030.

CONCLUSIONS

The combination of increased access to HCV testing, highly efficacious antiviral treatment and harm-reduction programs can substantially decrease the burden of the HCV epidemic among PWID. However, unless we increase the current levels of treatment and testing, the HCV epidemic among PWID in BC, and in other parts of the world with similar epidemiological background, will remain a substantial public health concern for many years.

HIV Treatment in Resource-Limited Environments: Treatment Coverage and Insights

BACKGROUND

The effects of antiretroviral treatment on the HIV epidemic are complex. HIV-infected individuals survive longer with treatment, but are less likely to transmit the disease. The standard coverage measure improves with the deaths of untreated individuals and does not consider the fact that some individuals may acquire the disease and die before receiving treatment, making it susceptible to overestimating the long-run performance of antiretroviral treatment programs.

OBJECTIVE

The objective was to propose an alternative coverage definition to better measure the long-run performance of HIV treatment programs.

METHODS

We introduced cumulative incidence-based coverage as an alternative to measure an HIV treatment program's success. To numerically compare the definitions, we extended a simulation model of HIV disease and treatment to represent a dynamic population that includes uninfected and HIV-infected individuals. Also, we estimated the additional resources required to implement various treatment policies in a resource-limited setting.

RESULTS

In a synthetic population of 600,000 people of which 44,000 (7.6%) are infected, and eligible for treatment with a CD4 count of less than 500 cells/mm(3), assuming a World Health Organization (WHO)-defined coverage rate of 50% of eligible people, and treating these individuals with a single treatment regimen, the gap between the current WHO coverage definition and our proposed one is as much as 16% over a 10-year planning horizon.

CONCLUSIONS

Cumulative incidence-based definition of coverage yields a more accurate representation of the long-run treatment success and along with the WHO and other definitions of coverage provides a better understanding of the HIV treatment progress.

Measuring the Potential Impact of Combination HIV Prevention in Sub-Saharan Africa

A public health approach to combination HIV prevention is advocated to contain the epidemic in sub-Saharan Africa. We explore the implications of universal access to treatment along with HIV education scale-up in the region. We develop an HIV transmission model to investigate the impacts of universal access to treatment, as well as an analytical framework to estimate the effects of HIV education scale-up on the epidemic. We calibrate the model with data from South Africa and simulate the impacts of universal access to treatment along with HIV education scale-up on prevalence, incidence, and HIV-related deaths over a course of 15 years. Our results show that the impact of combined interventions is significantly larger than the summation of individual intervention impacts (super-additive property). The combined strategy of universal access to treatment and HIV education scale-up decreases the incidence rate by 74% over the course of 15 years, whereas universal access to treatment and HIV education scale up will separately decrease that by 43% and 8%, respectively. Combination HIV prevention could be notably effective in transforming HIV epidemic to a low-level endemicity. Our results suggest that in designing effective combination prevention in sub-Saharan Africa, priorities should be given to achieving universal access to treatment as quickly as possible and improving compliance to condom use.

Reconciling the science and policy divide: The reality of scaling up antiretroviral therapy in South Africa

With the world’s largest national treatment programme and over 340 000 incident cases annually, the response to HIV in South Africa is hotly contested and there is sometimes a dissonance between activism, science and policy. Too often, policy, whilst well intentioned, is informed only by epidemiological data. The state of the healthcare system and sociocultural factors drive and shape the epidemic and its response. By analysis of the financial, infrastructural, human resources for health, and governance landscape in South Africa, we assess the feasibility and associated costs of implementing a universal test and treat programme. We situate a universal test and treat strategy within the governance, fiscal, human resources for health, and infrastructural landscape in South Africa. We argue that the response to the epidemic must be forward thinking, progressive and make the most of the benefits from treatment as prevention. However, the logistics of implementing a universal test and treat strategy mean that this option is problematic in the short term. We recommend a health systems strengthening HIV treatment and prevention approach that includes scaling up treatment (for treatment and prevention) along with a range of other prevention strategies.

Potential impact of existing interventions and of antiretroviral use in female sex workers on transmission of HIV in Burkina Faso: a modeling study

BACKGROUND

The impact and cost-effectiveness of antiretroviral treatment (ART) as prevention is likely to vary depending on the local context. Burkina Faso has a concentrated mature HIV epidemic where female sex workers (FSW) are thought to have driven HIV transmission.

METHODS

A dynamic HIV transmission model was developed using data from the Yerelon FSW cohort in Bobo-Dioulasso and population surveys. Compared with current ART provision [status quo (SQ)], the model estimated the proportion of HIV infections averted or incremental life-years gained per additional person-year of ART over 20 years for ART targeting different subgroups or expanding eligibility to all HIV-infected individuals compared with SQ.

RESULTS

Modeling suggests that condom use within commercial sex has averted 40% of past HIV infections. Continuing SQ averts 35%-47% of new infections over 20 years compared with no ART. Expanding ART eligibility to all HIV-infected individuals and increasing recruitment (80% per year) could avert a further 65% of new infections, whereas targeting full-time FSW or all FSWs achieved less impact but was more efficient in terms of life-years gained per 100 person-years of ART. Local HIV elimination is possible with expanded ART provision to FSWs but requires condom use within commercial sex to be maintained at high levels.

CONCLUSIONS

Increasing FSW recruitment onto ART could be a highly efficient method for reducing HIV transmission in concentrated epidemic settings but should not be undertaken at the expense of existing interventions for FSWs. Specialized clinics providing multiple interventions for FSWs should be a fundamental component of prevention in concentrated epidemics.

Creating an African HIV clinical research and prevention trials network: HIV prevalence, incidence and transmission

HIV epidemiology informs prevention trial design and program planning. Nine clinical research centers (CRC) in sub-Saharan Africa conducted HIV observational epidemiology studies in populations at risk for HIV infection as part of an HIV prevention and vaccine trial network. Annual HIV incidence ranged from below 2% to above 10% and varied by CRC and risk group, with rates above 5% observed in Zambian men in an HIV-discordant relationship, Ugandan men from Lake Victoria fishing communities, men who have sex with men, and several cohorts of women. HIV incidence tended to fall after the first three months in the study and over calendar time. Among suspected transmission pairs, 28% of HIV infections were not from the reported partner. Volunteers with high incidence were successfully identified and enrolled into large scale cohort studies. Over a quarter of new cases in couples acquired infection from persons other than the suspected transmitting partner.

HIV treatment as prevention: contradictory perspectives from dynamic mathematical models

The preventative effects of antiretroviral therapy for people with HIV have been debated since they were first raised. Models commenced studying the preventive effects of treatment in the 1990s, prior to initial public reports. However, the outcomes of the preventive effects of antiretroviral use were not consistent. Some outcomes of dynamic models were based on unfeasible assumptions, such as no consideration of drug resistance, behavior disinhibition, or economic inputs in poor countries, and unrealistic input variables, for example, overstated initiation time, adherence, coverage, and efficacy of treatment. This paper reviewed dynamic mathematical models to ascertain the complex effects of ART on HIV transmission. This review discusses more conservative inputs and outcomes relative to antiretroviral use in HIV infections in dynamic mathematical models. ART alone cannot eliminate HIV transmission.

Why the proportion of transmission during early-stage HIV infection does not predict the long-term impact of treatment on HIV incidence

Antiretroviral therapy (ART) reduces the infectiousness of HIV-infected persons, but only after testing, linkage to care, and successful viral suppression. Thus, a large proportion of HIV transmission during a period of high infectiousness in the first few months after infection ("early transmission") is perceived as a threat to the impact of HIV "treatment-as-prevention" strategies. We created a mathematical model of a heterosexual HIV epidemic to investigate how the proportion of early transmission affects the impact of ART on reducing HIV incidence. The model includes stages of HIV infection, flexible sexual mixing, and changes in risk behavior over the epidemic. The model was calibrated to HIV prevalence data from South Africa using a Bayesian framework. Immediately after ART was introduced, more early transmission was associated with a smaller reduction in HIV incidence rate--consistent with the concern that a large amount of early transmission reduces the impact of treatment on incidence. However, the proportion of early transmission was not strongly related to the long-term reduction in incidence. This was because more early transmission resulted in a shorter generation time, in which case lower values for the basic reproductive number (R0) are consistent with observed epidemic growth, and R0 was negatively correlated with long-term intervention impact. The fraction of early transmission depends on biological factors, behavioral patterns, and epidemic stage and alone does not predict long-term intervention impacts. However, early transmission may be an important determinant in the outcome of short-term trials and evaluation of programs.

What can mathematical models tell us about the relationship between circular migrations and HIV transmission dynamics?

Circular migrations are the periodic movement of individuals between multiple locations, observed in parts of sub-Saharan Africa. Relationships between circular migrations and HIV are complex, entailing interactions between migration frequency, partnership structure, and exposure to acute HIV infection. Mathematical modeling is a useful tool for understanding these interactions. Two modeling classes have dominated the HIV epidemiology and policy literature for the last decade: one a form of compartmental models, the other network models. We construct models from each class, using ordinary differential equations and exponential random graph models, respectively. Our analysis suggests that projected HIV prevalence is highly sensitive to the choice of modeling framework. Assuming initial equal HIV prevalence across locations, compartmental models show no association between migration frequency and HIV prevalence or incidence, while network models show that migrations at frequencies shorter than the acute HIV period predict greater HIV incidence and prevalence compared to longer migration periods. These differences are statistically significant when network models are extended to incorporate a requirement for migrant men's multiple partnerships to occur in different locations. In settings with circular migrations, commonly-used forms of compartmental models appear to miss key components of HIV epidemiology stemming from interactions of relational and viral dynamics.

Expanded HIV testing in low-prevalence, high-income countries: a cost-effectiveness analysis for the United Kingdom

Objective

In many high-income countries with low HIV prevalence, significant numbers of persons living with HIV (PLHIV) remain undiagnosed. Identification of PLHIV via HIV testing offers timely access to lifesaving antiretroviral therapy (ART) and decreases HIV transmission. We estimated the effectiveness and cost-effectiveness of HIV testing in the United Kingdom (UK), where 25% of PLHIV are estimated to be undiagnosed.

Design

We developed a dynamic compartmental model to analyze strategies to expand HIV testing and treatment in the UK, with particular focus on men who have sex with men (MSM), people who inject drugs (PWID), and individuals from HIV-endemic countries.

Methods

We estimated HIV prevalence, incidence, quality-adjusted life years (QALYs), and health care costs over 10 years, and cost-effectiveness.

Results

Annual HIV testing of all adults could avert 5% of new infections, even with no behavior change following HIV diagnosis because of earlier ART initiation, or up to 18% if risky behavior is halved. This strategy costs £67,000–£106,000/QALY gained. Providing annual testing only to MSM, PWID, and people from HIV-endemic countries, and one-time testing for all other adults, prevents 4–15% of infections, requires one-fourth as many tests to diagnose each PLHIV, and costs £17,500/QALY gained. Augmenting this program with increased ART access could add 145,000 QALYs to the population over 10 years, at £26,800/QALY gained.

Conclusions

Annual HIV testing of key populations in the UK is very cost-effective. Additional one-time testing of all other adults could identify the majority of undiagnosed PLHIV. These findings are potentially relevant to other low-prevalence, high-income countries.

Treatment as prevention among injecting drug users; extrapolating from the Amsterdam cohort study

OBJECTIVE

To determine the potential of treatment as prevention for reducing HIV incidence among injecting drug users (IDU).

METHODS

Transmission dynamics of HIV as influenced by cART uptake and demographic changes were studied using an individual-based model. Parameters were based on data of the Amsterdam Cohort Study, and counterfactual treatment scenarios were examined for this city. Demography of the modeled population was also varied to allow for more general conclusions.

RESULTS

We estimated that over the complete HIV epidemic among IDU in Amsterdam the historic use of cART has led to only 2% less incidence. As individuals were treated from low CD4 cell counts, their decreased infectiousness was offset by increased infectious lifetime. Large reduction in incidence could result from a test and immediate treat strategy, with elimination of HIV occurring when the average time from infection to starting treatment was less than 2 months. However, substantial proportions of new infections were prevented only if the test and treat intervention was implemented within the first few years after HIV-epidemic onset, especially for a declining IDU population. Ignoring heterogeneity in risk-behavior led to overly optimistic expectations of the prevention effects of treatment. In general, treatment led to much greater reduction in incidence compared with stopping HIV-infected IDU from lending out syringes.

CONCLUSION

A test and immediate treat strategy for HIV among IDU could lead to great reductions in incidence. To fully eliminate the spread of HIV, treatment as prevention should be combined with other interventions, with behavioral intervention directed at those not yet HIV infected.

Expansion of HAART coverage is associated with sustained decreases in HIV/AIDS morbidity, mortality and HIV transmission: the "HIV Treatment as Prevention" experience in a Canadian setting

Background

There has been renewed call for the global expansion of highly active antiretroviral therapy (HAART) under the framework of HIV treatment as prevention (TasP). However, population-level sustainability of this strategy has not been characterized.

Methods

We used population-level longitudinal data from province-wide registries including plasma viral load, CD4 count, drug resistance, HAART use, HIV diagnoses, AIDS incidence, and HIV-related mortality. We fitted two Poisson regression models over the study period, to relate estimated HIV incidence and the number of individuals on HAART and the percentage of virologically suppressed individuals.

Results

HAART coverage, median pre-HAART CD4 count, and HAART adherence increased over time and were associated with increasing virological suppression and decreasing drug resistance. AIDS incidence decreased from 6.9 to 1.4 per 100,000 population (80% decrease, p = 0.0330) and HIV-related mortality decreased from 6.5 to 1.3 per 100,000 population (80% decrease, p = 0.0115). New HIV diagnoses declined from 702 to 238 cases (66% decrease; p = 0.0004) with a consequent estimated decline in HIV incident cases from 632 to 368 cases per year (42% decrease; p = 0.0003). Finally, our models suggested that for each increase of 100 individuals on HAART, the estimated HIV incidence decreased 1.2% and for every 1% increase in the number of individuals suppressed on HAART, the estimated HIV incidence also decreased by 1%.

Conclusions

Our results show that HAART expansion between 1996 and 2012 in BC was associated with a sustained and profound population-level decrease in morbidity, mortality and HIV transmission. Our findings support the long-term effectiveness and sustainability of HIV treatment as prevention within an adequately resourced environment with no financial barriers to diagnosis, medical care or antiretroviral drugs. The 2013 Consolidated World Health Organization Antiretroviral Therapy Guidelines offer a unique opportunity to further evaluate TasP in other settings, particularly within generalized epidemics, and resource-limited setting, as advocated by UNAIDS.

Challenges and potential barriers to the uptake of antiretroviral-based prevention in Asia and the Pacific region

Evidence has emerged over the past few years on the effectiveness of antiretroviral-based prevention technologies to prevent (i) HIV transmission while decreasing morbidity and mortality in HIV-infected persons, and (ii) HIV acquisition in HIV-uninfected individuals through pre-exposure prophylaxis (PrEP). Only few of the planned studies on treatment as prevention (TasP) are conducted in Asia. TasP might be more feasible and effective in concentrated rather than in generalised epidemics, as resources for HIV testing and antiretroviral treatment could focus on confined and much smaller populations than in the generalised epidemics observed in sub-Saharan Africa. Several countries such as Cambodia, China, Thailand and Vietnam, are now paving the way to success. Similar challenges arise for both TasP and PrEP. However, the operational issues for PrEP are amplified by the need for frequent retesting and ensuring adherence. This paper describes challenges for the implementation of antiretroviral-based prevention and makes the case that TasP and PrEP implementation research in Asia is much needed to provide insights into the feasibility of these interventions in populations where firm evidence of ‘real world’ effectiveness is still lacking.

Antiretroviral drug regimens to prevent mother-to-child transmission of HIV: a review of scientific, program, and policy advances for sub-Saharan Africa

Considerable advances have been made in the effort to prevent mother-to-child HIV transmission (PMTCT) in sub-Saharan Africa. Clinical trials have demonstrated the efficacy of antiretroviral regimens to interrupt HIV transmission through the antenatal, intrapartum, and postnatal periods. Scientific discoveries have been rapidly translated into health policy, bolstered by substantial investment in health infrastructure capable of delivering increasingly complex services. A new scientific agenda is also emerging, one that is focused on the challenges of effective and sustainable program implementation. Finally, global campaigns to "virtually eliminate" pediatric HIV and dramatically reduce HIV-related maternal mortality have mobilized new resources and renewed political will. Each of these developments marks a major step in regional PMTCT efforts; their convergence signals a time of rapid progress in the field, characterized by an increased interdependency between clinical research, program implementation, and policy. In this review, we take stock of recent advances across each of these areas, highlighting the challenges--and opportunities--of improving health services for HIV-infected mothers and their children across the region.

Resistance to protease inhibitors in a model of HIV-1 infection with impulsive drug effects

BACKGROUND

The emergence of drug resistance is one of the most prevalent reasons for treatment failure in HIV therapy. This has severe implications for the cost of treatment, survival and quality of life.

METHODS

We use mathematical modelling to describe the interaction between T cells, HIV-1 and protease inhibitors. We use impulsive differential equations to examine the effects of different levels of protease inhibitors in a T cell. We classify three different regimes according to whether the drug efficacy is low, intermediate or high. The model includes two strains: the wild-type strain, which initially dominates in the absence of drugs, and the mutant strain, which is the less efficient competitor, but has more resistance to the drugs.

RESULTS

Drug regimes may take trajectories through one, two or all three regimes, depending on the dosage and the dosing schedule. Stability analysis shows that resistance does not emerge at low drug levels. At intermediate drug levels, drug resistance is guaranteed to emerge. At high drug levels, either the drug-resistant strain will dominate or, in the absence of longer-lived reservoirs of infected cells, a region exists where viral elimination could theoretically occur. We provide estimates of a range of dosages and dosing schedules where the trajectories lie either solely within a region or cross multiple regions.

CONCLUSION

Under specific circumstances, if the drug level is physiologically tolerable, elimination of free virus is theoretically possible. This forms the basis for theoretical control using combination therapy and for understanding the effects of partial adherence.

Antiretroviral treatment of HIV-1 prevents transmission of HIV-1: where do we go from here?

Antiretroviral drugs that inhibit viral replication were expected to reduce transmission of HIV by lowering the concentration of HIV in the genital tract. In 11 of 13 observational studies, antiretroviral therapy (ART) provided to an HIV-infected index case led to greatly reduced transmission of HIV to a sexual partner. In the HPTN 052 randomised controlled trial, ART used in combination with condoms and counselling reduced HIV transmission by 96·4%. Evidence is growing that wider, earlier initiation of ART could reduce population-level incidence of HIV. However, the full benefits of this strategy will probably need universal access to very early ART and excellent adherence to treatment. Challenges to this approach are substantial. First, not all HIV-infected individuals can be located, especially people with acute and early infection who are most contagious. Second, the ability of ART to prevent HIV transmission in men who have sex with men (MSM) and people who use intravenous drugs has not been shown. Indeed, the stable or increased incidence of HIV in MSM in some communities where widespread use of ART has been established emphasises the concern that not enough is known about treatment as prevention for this crucial population. Third, although US guidelines call for immediate use of ART, such guidelines have not been embraced worldwide. Some experts do not believe that immediate or early ART is justified by present evidence, or that health-care infrastructure for this approach is sufficient. These concerns are very difficult to resolve. Ongoing community-based prospective trials of early ART are likely to help to establish the population-level benefit of ART, and-if successful-to galvanise treatment as prevention.

Modeling the cost-effectiveness of HIV treatment: how to buy the most 'health' when resources are limited

PURPOSE OF REVIEW

To summarize recent cost-effectiveness analyses (CEAs) that evaluate optimal treatment strategies for persons living with HIV/AIDS (PLWHA).

RECENT FINDINGS

Efforts to attain universal coverage of current treatment guidelines (e.g., initiation at CD4 cell count <350 cells/μl) are generally very costeffective. Expansion of access beyond current guidelines will additionally improve clinical outcomes and aversion of new HIV infections; however, cost-effectiveness is more uncertain. Increasing access to antiretroviral therapy (ART) offers greater health benefit than investing the same funds in intensive laboratory monitoring for those on ART, particularly in those settings in which universal coverage has not yet been attained. Recommended ART regimens (e.g., tenofovir) have favorable cost-effectiveness when compared with substitution of newer, more expensive agents (e.g., rilpivirine, darunavir) or substitution of older, cheaper alternatives that are more toxic (e.g., stavudine).

SUMMARY

There is increasing use of CEA to evaluate decisions regarding HIV treatment in order to buy the most 'health' with limited resources. Expansion of ART access provides substantial clinical and preventive benefit and offers favorable cost-effectiveness. Intensive laboratory monitoring may not be the highest priority in settings in which resources are constrained. Further work on the economic impact, clinical effectiveness, and feasibility of ART treatment for all (e.g., no CD4 cell initiation criteria) is needed.

Increasing survival time decreases the cost-effectiveness of using "test & treat'' to eliminate HIV epidemics

Treating HIV-infected individuals reduces their viral load, consequently increasing their survival time and decreasing their infectivity. It has been proposed that universal testing and treatment (i.e., universal "test & treat'') could lead to HIV elimination and would be extremely cost-effective. It is now being debated whether to use a universal "test & treat'' approach in the "real-world'' as a prevention strategy to control HIV epidemics. However current modeling predictions of the impact, and cost-effectiveness, of universal `"est & treat'' strategies are based on an unrealistically short survival time for treated individuals. Here we use mathematical modeling and a longer, more realistic, survival time. We model the potential impact of a universal "test & treat'' strategy in South Africa. Our results show that increasing the length of the survival time on treatment, although beneficial to individuals, reduces the probability of eliminating HIV and decreases the cost-effectiveness of using universal "test & treat'' strategies. Therefore our results show that individual-level benefits and public health benefits will conflict when using "test &treat'' strategies to reduce HIV transmission.

Combination prevention: new hope for stopping the epidemic

HIV research has identified approaches that can be combined to be more effective in transmission reduction than any 1 modality alone: delayed adolescent sexual debut, mutual monogamy or sexual partner reduction, correct and consistent condom use, pre-exposure prophylaxis with oral antiretroviral drugs or vaginal microbicides, voluntary medical male circumcision, antiretroviral therapy (ART) for prevention (including prevention of mother to child HIV transmission [PMTCT]), treatment of sexually transmitted infections, use of clean needles for all injections, blood screening prior to donation, a future HIV prime/boost vaccine, and the female condom. The extent to which evidence-based modalities can be combined to prevent substantial HIV transmission is largely unknown, but combination approaches that are truly implementable in field conditions are likely to be far more effective than single interventions alone. Analogous to PMTCT, "treatment as prevention" for adult-to-adult transmission reduction includes expanded HIV testing, linkage to care, antiretroviral coverage, retention in care, adherence to therapy, and management of key co-morbidities such as depression and substance use. With successful viral suppression, persons with HIV are far less infectious to others, as we see in the fields of sexually transmitted infection control and mycobacterial disease control (tuberculosis and leprosy). Combination approaches are complex, may involve high program costs, and require substantial global commitments. We present a rationale for such investments and cite an ongoing research agenda that seeks to determine how feasible and cost-effective a combination prevention approach would be in a variety of epidemic contexts, notably that in a sub-Saharan Africa.

Nested model reveals potential amplification of an HIV epidemic due to drug resistance

The use of antiretroviral therapy (ART) is the most efficient measure in controlling the HIV epidemic. However, emergence of drug-resistant strains can reduce the potential benefits of ART. The viral dynamics of drug-sensitive and drug-resistant strains at the individual level may play a crucial role in the emergence and spread of drug resistance in a population. We investigate the effect of the viral dynamics within an infected individual on the epidemiological dynamics of HIV using a nested model that links both dynamical levels. A time-dependent between-host transmission rate that receives feedback from a model of two-strain virus dynamics within a host is incorporated into an epidemiological model of HIV. We analyze the resulting dynamics of the model and identify model parameters such as time when ART is initiated, fraction of cases treated, and the probability that a patient develops drug resistance, as having the greatest impact on total infection and prevalence of drug resistance. Importantly, for small values of the risk of a patient developing drug resistance, increasing the fraction of cases treated can increase the cumulative number of infected individuals. Such a pattern is the result of the balance between not treating a patient and having future cases still sensitive to treatment, and treating the patient and increasing the chances for future (untreatable) drug-resistant infections. The current modeling framework incorporates important aspects of virus dynamics within a host into an epidemic model. This approach provides useful insights on the drug resistance dynamics of an epidemic of HIV, which may assist in identifying an optimal use of ART.