Exploring the HIV epidemic among key populations in Latin America

The work is focussed on the HIV epidemic among key populations in Latin America, a region that has received limited international attention due to the concentrated nature of its epidemic. It faces important challenges in prevention and risks missing the opportunity to control the epidemic. Despite the evidence available showing the disproportionate burden of infection among key populations, principally men who have sex with men (MSM) and to a lesser extent injecting drug users (IDU) and female sex workers (FSW), a small percentage of countries’ HIV prevention spending is allocated towards prevention interventions among these groups. In this thesis, we first estimate the distribution of new infections by type of exposure in the Dominican Republic, Mexico and Peru and find that MSM account for a large share of new infections in the three countries (over 50% in Mexico and Peru and 30% in Dominican Republic). This highlights that this population should be prioritised in prevention programmes. We then turn to interventions for MSM, and investigate whether pre-exposure prophylaxis (PrEP) to prevent HIV acquisition among MSM in Lima, Peru represents a cost-effective intervention at the population level. We find PrEP to be a potentially cost-effective intervention although unaffordable at a large scale. We conclude it should be considered as an additional tool within a combination prevention approach among this population. Following these, we seek to understand the dynamics, causes and consequences of risk behaviours and HIV infection in another key population that has rarely been prioritised by public health programmes: prison inmates. We use data from the largest prison in Peru and find that HIV prevalence is 4 times higher than national prevalence and inmates engage in riskier sexual behaviours than in the general population. Nevertheless, there are indications of risk behaviours and HIV prevalence reducing in recent years. To help direct prevention efforts in this setting, we characterise the risk profile of inmates who engaged in sex with FSW, other men and in unprotected sex with casual partners and identify inmates who have sex with men as being at heightened risk of infection (due to higher levels of drug use and unprotected sex). We use those data to develop a mathematical model that represents the HIV epidemic in the prison. Contrary to expectations, we find that incidence is likely to be less than 1% per year within the prison and that the dynamics of HIV in prisons are principally driven by inmates infected before their incarceration. We further estimate that since the beginning of the epidemic, at least 5% of HIV cases identified in Lima have passed through the prison, suggesting that the routine screening system in place at prisons could make a substantial contribution to controlling the HIV epidemic across the city. Finally, we formulate a conceptual framework of HIV risk among prison inmates in Latin America focussing on the social and underlying determinants of risk and develop a structured questionnaire to test the hypotheses proposed through the framework and obtain information relevant to the design of interventions within prisons and at the community level. Together this work draws on social and quantitative science to provide new insights into key populations in Latin America that should contribute to stronger and responsive HIV prevention programmes, to the benefit of all those that remain at risk of HIV in the region

The Incidence Patterns Model to Estimate the Distribution of New HIV Infections in Sub-Saharan Africa: Development and Validation of a Mathematical Model.

BACKGROUND: Programmatic planning in HIV requires estimates of the distribution of new HIV infections according to identifiable characteristics of individuals. In sub-Saharan Africa, robust routine data sources and historical epidemiological observations are available to inform and validate such estimates. METHODS AND FINDINGS: We developed a predictive model, the Incidence Patterns Model (IPM), representing populations according to factors that have been demonstrated to be strongly associated with HIV acquisition risk: gender, marital/sexual activity status, geographic location, "key populations" based on risk behaviours (sex work, injecting drug use, and male-to-male sex), HIV and ART status within married or cohabiting unions, and circumcision status. The IPM estimates the distribution of new infections acquired by group based on these factors within a Bayesian framework accounting for regional prior information on demographic and epidemiological characteristics from trials or observational studies. We validated and trained the model against direct observations of HIV incidence by group in seven rounds of cohort data from four studies ("sites") conducted in Manicaland, Zimbabwe; Rakai, Uganda; Karonga, Malawi; and Kisesa, Tanzania. The IPM performed well, with the projections' credible intervals for the proportion of new infections per group overlapping the data's confidence intervals for all groups in all rounds of data. In terms of geographical distribution, the projections' credible intervals overlapped the confidence intervals for four out of seven rounds, which were used as proxies for administrative divisions in a country. We assessed model performance after internal training (within one site) and external training (between sites) by comparing mean posterior log-likelihoods and used the best model to estimate the distribution of HIV incidence in six countries (Gabon, Kenya, Malawi, Rwanda, Swaziland, and Zambia) in the region. We subsequently inferred the potential contribution of each group to transmission using a simple model that builds on the results from the IPM and makes further assumptions about sexual mixing patterns and transmission rates. In all countries except Swaziland, individuals in unions were the single group contributing to the largest proportion of new infections acquired (39%-77%), followed by never married women and men. Female sex workers accounted for a large proportion of new infections (5%-16%) compared to their population size. Individuals in unions were also the single largest contributor to the proportion of infections transmitted (35%-62%), followed by key populations and previously married men and women. Swaziland exhibited different incidence patterns, with never married men and women accounting for over 65% of new infections acquired and also contributing to a large proportion of infections transmitted (up to 56%). Between- and within-country variations indicated different incidence patterns in specific settings. CONCLUSIONS: It is possible to reliably predict the distribution of new HIV infections acquired using data routinely available in many countries in the sub-Saharan African region with a single relatively simple mathematical model. This tool would complement more specific analyses to guide resource allocation, data collection, and programme planning

Hispanic Latin America, Spain and the Spanish-speaking Caribbean: A rich source of reference material for public health, epidemiology and tropical medicine

There is a multiplicity of journals originating in Spain and the Spanish-speaking countries of Latin America and the Caribbean (SSLAC) in the health sciences of relevance to the fields of epidemiology and public health. While the subject matter of epidemiology in Spain shares many features with its neighbours in Western Europe, many aspects of epidemiology in Latin America are particular to that region. There are also distinctive theoretical and philosophical approaches to the study of epidemiology and public health arising from traditions such as the Latin American social medicine movement, of which there may be limited awareness. A number of online bibliographic databases are available which focus primarily on health sciences literature arising in Spain and Latin America, the most prominent being Literatura Latinoamericana en Ciencias de la Salud (LILACS) and LATINDEX. Some such as LILACS also extensively index grey literature. As well as in Spanish, interfaces are provided in English and Portuguese. Abstracts of articles may also be provided in English with an increasing number of journals beginning to publish entire articles written in English. Free full text articles are becoming accessible, one of the most comprehensive sources being the Scientific Electronic Library Online (SciELO). There is thus an extensive range of literature originating in Spain and SSLAC freely identifiable and often accessible online, and with the potential to provide useful inputs to the study of epidemiology and public health provided that any reluctance to explore these resources can be overcome. In this article we provide an introduction to such resources

Characterizing Help-Seeking Searches for Substance Use Treatment From Google Trends and Assessing Their Use for Infoveillance: Longitudinal Descriptive and Validation Statistical Analysis.

BackgroundThere is no recognized gold standard method for estimating the number of individuals with substance use disorders (SUDs) seeking help within a given geographical area. This presents a challenge to policy makers in the effective deployment of resources for the treatment of SUDs. Internet search queries related to help seeking for SUDs using Google Trends may represent a low-cost, real-time, and data-driven infoveillance tool to address this shortfall in information.ObjectiveThis paper assesses the feasibility of using search query data related to help seeking for SUDs as an indicator of unmet treatment needs, demand for treatment, and predictor of the health harms related to unmet treatment needs. We explore a continuum of hypotheses to account for different outcomes that might be expected to occur depending on the demand for treatment relative to the system capacity and the timing of help seeking in relation to trajectories of substance use and behavior change.MethodsWe used negative binomial regression models to examine temporal trends in the annual SUD help-seeking internet search queries from Google Trends by US state for cocaine, methamphetamine, opioids, cannabis, and alcohol from 2010 to 2020. To validate the value of these data for surveillance purposes, we then used negative binomial regression models to investigate the relationship between SUD help-seeking searches and state-level outcomes across the continuum of care (including lack of care). We started by looking at associations with self-reported treatment need using data from the National Survey on Drug Use and Health, a national survey of the US general population. Next, we explored associations with treatment admission rates from the Treatment Episode Data Set, a national data system on SUD treatment facilities. Finally, we studied associations with state-level rates of people experiencing and dying from an opioid overdose, using data from the Agency for Healthcare Research and Quality and the CDC WONDER database.ResultsStatistically significant differences in help-seeking searches were observed over time between 2010 and 2020 (based on P<.05 for the corresponding Wald tests). We were able to identify outlier states for each drug over time (eg, West Virginia for both opioids and methamphetamine), indicating significantly higher help-seeking behaviors compared to national trends. Results from our validation analyses across different outcomes showed positive, statistically significant associations for the models relating to treatment need for alcohol use, treatment admissions for opioid and methamphetamine use, emergency department visits related to opioid use, and opioid overdose mortality data (based on regression coefficients having P≤.05).ConclusionsThis study demonstrates the clear potential for using internet search queries from Google Trends as an infoveillance tool to predict the demand for substance use treatment spatially and temporally, especially for opioid use disorders

Methodological approaches for the prediction of opioid use-related epidemics in the United States: a narrative review and cross-disciplinary call to action.

The opioid crisis in the United States has been defined by waves of drug- and locality-specific Opioid use-Related Epidemics (OREs) of overdose and bloodborne infections, among a range of health harms. The ability to identify localities at risk of such OREs, and better yet, to predict which ones will experience them, holds the potential to mitigate further morbidity and mortality. This narrative review was conducted to identify and describe quantitative approaches aimed at the "risk assessment," "detection" or "prediction" of OREs in the United States. We implemented a PubMed search composed of the: (1) objective (eg, prediction), (2) epidemiologic outcome (eg, outbreak), (3) underlying cause (ie, opioid use), (4) health outcome (eg, overdose, HIV), (5) location (ie, US). In total, 46 studies were included, and the following information extracted: discipline, objective, health outcome, drug/substance type, geographic region/unit of analysis, and data sources. Studies identified relied on clinical, epidemiological, behavioral and drug markets surveillance and applied a range of methods including statistical regression, geospatial analyses, dynamic modeling, phylogenetic analyses and machine learning. Studies for the prediction of overdose mortality at national/state/county and zip code level are rapidly emerging. Geospatial methods are increasingly used to identify hotspots of opioid use and overdose. In the context of infectious disease OREs, routine genetic sequencing of patient samples to identify growing transmission clusters via phylogenetic methods could increase early detection capacity. A coordinated implementation of multiple, complementary approaches would increase our ability to successfully anticipate outbreak risk and respond preemptively. We present a multi-disciplinary framework for the prediction of OREs in the US and reflect on challenges research teams will face in implementing such strategies along with good practices

Estimación y análisis de la incidencia de VIH en población adulta del Perú: resultados de la aplicación del modelo matemático MoT

Objectives. To estimate HIV incidence in the adult population of Peru, 2010, and analyze its distribution based on risk behavior. Materials and methods. The UNAIDS model was applied based on the modes of transmission (MoT). The information was obtained from the review detailed in 59 documents (1984 – 2008). National databases were also analyzed to obtain specific data. Final selection of data was validated by the technical group and a group of experts. After consultation with experts, values were corrected and an uncertainty analysis was conducted. The model was adjusted to 2009 national prevalence (0.45%). Results. Incidence estimated for 2010 was 0.03%, (4346 new infections). 84% of new infections concentrate on higher risk groups: men who have sex with men (55%) and people who have casual sex with heterosexuals (6.2%). The remaining 16% corresponds to low-risk heterosexual population. Heterosexual transmission accounts for 43% of new cases, 18% of which corresponds to female partners of high risk individuals. Only 2.2% of cases is related to female sexual work and 1.0% to injection drug users. Conclusions. The model provides an estimation of the incidence and its distribution among risk groups according to the mode of transmission, consistent with the HIV case reporting. The model creates scenarios to help decision making and policy formulation, as well as surveillance and planning of prevention and control.Objetivos. Estimar la incidencia de VIH en la población adulta del Perú, 2010, y analizar su distribución según comportamientos de riesgo. Materiales y métodos. Se aplicó el modelo de ONUSIDA según modos de transmisión (MoT). Los datos fueron obtenidos de la revisión detallada de 59 documentos (1984 – 2008). También se analizó bases de datos nacionales para obtener datos específicos. La selección final de los datos fue validada por el grupo técnico y un grupo de expertos. Después de la consulta con expertos, se corrigieron los valores y se realizó un análisis de incertidumbre. El modelo fue ajustado a la prevalencia nacional del 2009 (0,45%). Resultados. La incidencia estimada para el 2010 fue de 0,03%, (4346 nuevas infecciones). El 84% de nuevas infecciones se concentra en grupos de mayor riesgo: hombres que tienen sexo con hombres (55%) y personas que tienen sexo casual heterosexual (6,2%). El 16% restante corresponde a la población heterosexual de bajo riesgo. La transmisión heterosexual es el 43% de nuevos casos, y dentro de estos el 18% corresponde a parejas femeninas de sujetos de alto riesgo. Solo 2,2% de casos está relacionado al trabajo sexual femenino y 1,0% a usuarios de drogas inyectables. Conclusiones. El modelo proporciona una estimación de la incidencia y su distribución entre los grupos de riesgo según el modo de transmisión, consistente con los reportes de casos de VIH. El modelo permite crear escenarios para ayudar a la toma de decisiones y formulación de políticas, así como para vigilancia y planificación de la prevención y control

Estimación y análisis de la incidencia de VIH en población adulta del Perú: resultados de la aplicación del modelo matemático MoT Estimation and analysis of HIV incidence in the adult population in Peru: results of application of the MoT mathematical model

Objetivos. Estimar la incidencia de VIH en la población adulta del Perú, 2010, y analizar su distribución según comportamientos de riesgo. Materiales y métodos. Se aplicó el modelo de ONUSIDA según modos de transmisión (MoT). Los datos fueron obtenidos de la revisión detallada de 59 documentos (1984 - 2008). También se analizó bases de datos nacionales para obtener datos específicos. La selección final de los datos fue validada por el grupo técnico y un grupo de expertos. Después de la consulta con expertos, se corrigieron los valores y se realizó un análisis de incertidumbre. El modelo fue ajustado a la prevalencia nacional del 2009 (0,45%). Resultados. La incidencia estimada para el 2010 fue de 0,03%, (4346 nuevas infecciones). El 84% de nuevas infecciones se concentra en grupos de mayor riesgo: hombres que tienen sexo con hombres (55%) y personas que tienen sexo casual heterosexual (6,2%). El 16% restante corresponde a la población heterosexual de bajo riesgo. La transmisión heterosexual es el 43% de nuevos casos, y dentro de estos el 18% corresponde a parejas femeninas de sujetos de alto riesgo. Solo 2,2% de casos está relacionado al trabajo sexual femenino y 1,0% a usuarios de drogas inyectables. Conclusiones. El modelo proporciona una estimación de la incidencia y su distribución entre los grupos de riesgo según el modo de transmisión, consistente con los reportes de casos de VIH. El modelo permite crear escenarios para ayudar a la toma de decisiones y formulación de políticas, así como para vigilancia y planificación de la prevención y control.Objectives. To estimate HIV incidence in the adult population of Peru, 2010, and analyze its distribution based on risk behavior. Materials and methods. The UNAIDS model was applied based on the modes of transmission (MoT). The information was obtained from the review detailed in 59 documents (1984 - 2008). National databases were also analyzed to obtain specific data. Final selection of data was validated by the technical group and a group of experts. After consultation with experts, values were corrected and an uncertainty analysis was conducted. The model was adjusted to 2009 national prevalence (0.45%). Results. Incidence estimated for 2010 was 0.03%, (4346 new infections). 84% of new infections concentrate on higher risk groups: men who have sex with men (55%) and people who have casual sex with heterosexuals (6.2%). The remaining 16% corresponds to low-risk heterosexual population. Heterosexual transmission accounts for 43% of new cases, 18% of which corresponds to female partners of high risk individuals. Only 2.2% of cases is related to female sexual work and 1.0% to injection drug users. Conclusions. The model provides an estimation of the incidence and its distribution among risk groups according to the mode of transmission, consistent with the HIV case reporting. The model creates scenarios to help decision making and policy formulation, as well as surveillance and planning of prevention and control

Syringe sharing among people who inject drugs in Tijuana: before and after the Global Fund

Introduction. Needle and syringe programs (NSP) reduce syringe sharing and HIV transmission among people who inject drugs (PWID). However, their effectiveness relies on sufficient individual and population level coverage. In Tijuana, Mexico, the Global Fund (GF) supported NSP during 10/2011-12/2013, but withdrew funds at the end of 2013 following Mexico’s re-classification as an upper-middle income country. Objective. We tested the hypothesis of higher NSP access and lower receptive syringe sharing among PWID in Tijuana during the GF support period compared to pre-GF initiation and post-GF withdrawal. Method. We used data from an ongoing cohort study of PWID in Tijuana (03/2011-10/2015) to implement a segmented regression analysis investigating changes in the self-reported probability of NSP access, reported difficulty in finding sterile syringes and receptive syringe sharing before GF initiation and after GF discontinuation. Results. We found a large significant increase in the probability of NSP access (+.07) and decrease in receptive syringe sharing (-.23) right after GF initiation, which continued over the GF period. Subsequently, we found a significant decline in NSP access (-.05) and an increase in receptive syringe sharing (+.02) right after post-GF withdrawal, which continued thereafter. Discussion and conclusion. We demonstrated significant temporal changes in NSP access and receptive syringe sharing among PWID in Tijuana after GF initiation and withdrawal consistent with our hypothesis. Coordinated efforts with local authorities are needed to sustain major coverage NSP in settings receiving GF or external aid to guarantee continuity of harm reduction services and prevent reinside in risk behaviors associated with HIV transmission

Modelling integrated antiretroviral treatment and harm reduction services on HIV and overdose among people who inject drugs in Tijuana, Mexico

IntroductionThe HIV epidemic in Tijuana, Mexico is concentrated in key populations, including people who inject drugs (PWID). However, HIV interventions among PWID are minimal, and federal funding was provided for compulsory abstinence programmes associated with HIV and overdose. Alternatively, opioid agonist therapy reduces overdose, reincarceration, HIV, while improving antiretroviral therapy (ART) outcomes. We assessed potential impact and synergies of scaled-up integrated ART and opioid agonist therapy, compared to scale-up of each separately, and potential harms of compulsory abstinence programmes on HIV and fatal overdose among PWID in Tijuana.MethodsWe developed a dynamic model of HIV transmission and overdose among PWID in Tijuana. We simulated scale-up of opioid agonist therapy from zero to 40% coverage among PWID. We evaluated synergistic benefits of an integrated harm reduction and ART scale-up strategy (40% opioid agonist therapy coverage and 10-fold ART recruitment), compared to scale-up of each intervention alone or no scale-up of low coverage ART and no harm reduction). We additionally simulated compulsory abstinence programmes (associated with 14% higher risk of receptive syringe sharing and 76% higher odds of overdose) among PWID.ResultsWithout intervention, HIV incidence among PWID could increase from 0.72 per 100 person-years (PY) in 2020 to 0.92 per 100 PY in 2030. Over ten years, opioid agonist therapy scale-up could avert 31% (95% uncertainty interval (UI): 18%, 46%) and 22% (95% UI: 10%, 28%) new HIV infections and fatal overdoses, respectively, with the majority of HIV impact from the direct effect on HIV transmission due to low ART coverage. Integrating opioid agonist therapy and ART scale-up provided synergistic benefits, with opioid agonist therapy effects on ART recruitment/retention averting 9% more new infections compared to ART scale-up alone. The intervention strategy could avert 48% (95% UI: 26%, 68%) of new HIV infections and one-fifth of fatal overdoses over ten years. Conversely, compulsory abstinence programmes could increase HIV and overdoses.ConclusionsIntegrating ART with opioid agonist therapy could provide synergistic benefits and prevent HIV and overdoses among PWID in Tijuana, whereas compulsory abstinence programmes could cause harm. Policymakers should consider the benefits of integrating harm reduction and HIV services for PWID