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      Understanding the modes of transmission model of new HIV infection and its use in prevention planning Translated title: Comprendre le modèle des modes de transmission des nouvelles infections par le VIH et son utilisation dans les plans de prévention Translated title: Entender el modelo de los modos de transmisión de las infecciones nuevas por VIH y su uso en los planes de prevención

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          Abstract

          The modes of transmission model has been widely used to help decision-makers target measures for preventing human immunodeficiency virus (HIV) infection. The model estimates the number of new HIV infections that will be acquired over the ensuing year by individuals in identified risk groups in a given population using data on the size of the groups, the aggregate risk behaviour in each group, the current prevalence of HIV infection among the sexual or injecting drug partners of individuals in each group, and the probability of HIV transmission associated with different risk behaviours. The strength of the model is its simplicity, which enables data from a variety of sources to be synthesized, resulting in better characterization of HIV epidemics in some settings. However, concerns have been raised about the assumptions underlying the model structure, about limitations in the data available for deriving input parameters and about interpretation and communication of the model results. The aim of this review was to improve the use of the model by reassessing its paradigm, structure and data requirements. We identified key questions to be asked when conducting an analysis and when interpreting the model results and make recommendations for strengthening the model's application in the future.

          Translated abstract

          RÉSUMÉ Le modèle de modes de transmission a été largement utilisé pour aider les décideurs à cibler les mesures empêchant l'infection par le virus d'immunodéficience humaine (VIH). Le modèle estime le nombre de nouvelles infections par le VIH au cours de l'année suivante, contractées par des individus appartenant aux groupes à risque identifiés d'une population donnée, en utilisant des données sur la taille des groupes, le comportement à risque global de chaque groupe, la prévalence actuelle de l'infection par le VIH entre partenaires sexuels ou d'injection de drogues de chaque groupe, et la probabilité de transmission du VIH associée aux divers comportements à risque. La force du modèle réside dans sa simplicité, permettant de synthétiser des données provenant d'une variété de sources, ce qui donne une meilleure caractérisation de l'épidémie du VIH dans certains contextes. Toutefois, des problèmes ont été relevés concernant les hypothèses qui sous-tendent la structure du modèle, les limites des données disponibles pour obtenir les paramètres d'entrée, ainsi que l'interprétation et la communication des résultats du modèle. L'objectif de la présente étude était d'améliorer l'utilisation du modèle en réévaluant son paradigme, sa structure et ses exigences en termes de données. Nous avons identifié les principales questions à poser lors de l'analyse et de l'interprétation des résultats du modèle, et nous faisons des recommandations visant à renforcer l'application du modèle à l'avenir.

          Translated abstract

          El modelo de los modos de transmisión se ha empleado de manera generalizada para ayudar a los responsables de la toma de decisiones a dirigir las medidas para la prevención de la infección por el virus de la inmunodeficiencia humana (VIH). El modelo calcula el número de infecciones por VIH nuevas adquiridas durante el año subsiguiente por individuos en grupos de riesgo identificados en una población dada empleando datos acerca del tamaño de los grupos, el comportamiento de riesgo conjunto en cada grupo, la prevalencia actual de la infección por VIH entre las parejas sexuales o personas que comparten jeringuillas para el consumo de drogas de los individuos de cada grupo y la probabilidad de trasmitir el VIH asociada a los diferentes comportamientos de riesgo. El punto fuerte del modelo es su sencillez, que permite sintetizar datos de fuentes variadas, de lo que resulta una caracterización más exacta de la epidemia del VIH en algunos entornos. No obstante, han surgido dudas acerca de las suposiciones que subyacen a la estructura del modelo, las limitaciones de los datos disponibles para derivar de ellos parámetros de entrada y la interpretación y comunicación de los resultados del modelo. El objeto de este examen fue el de mejorar el uso del modelo volviendo a examinar su paradigma, su estructura y los requisitos de los datos. Identificamos los puntos clave que deben cuestionarse durante la realización de un análisis y la interpretación de los resultados del modelo y formulamos recomendaciones para consolidar la aplicación del modelo en el futuro

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          Most cited references 50

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          Heterosexual risk of HIV-1 infection per sexual act: systematic review and meta-analysis of observational studies.

          We did a systematic review and meta-analysis of observational studies of the risk of HIV-1 transmission per heterosexual contact. 43 publications comprising 25 different study populations were identified. Pooled female-to-male (0.04% per act [95% CI 0.01-0.14]) and male-to-female (0.08% per act [95% CI 0.06-0.11]) transmission estimates in high-income countries indicated a low risk of infection in the absence of antiretrovirals. Low-income country female-to-male (0.38% per act [95% CI 0.13-1.10]) and male-to-female (0.30% per act [95% CI 0.14-0.63]) estimates in the absence of commercial sex exposure (CSE) were higher. In meta-regression analysis, the infectivity across estimates in the absence of CSE was significantly associated with sex, setting, the interaction between setting and sex, and antenatal HIV prevalence. The pooled receptive anal intercourse estimate was much higher (1.7% per act [95% CI 0.3-8.9]). Estimates for the early and late phases of HIV infection were 9.2 (95% CI 4.5-18.8) and 7.3 (95% CI 4.5-11.9) times larger, respectively, than for the asymptomatic phase. After adjusting for CSE, presence or history of genital ulcers in either couple member increased per-act infectivity 5.3 (95% CI 1.4-19.5) times versus no sexually transmitted infection. Study estimates among non-circumcised men were at least twice those among circumcised men. Low-income country estimates were more heterogeneous than high-income country estimates, which indicates poorer study quality, greater heterogeneity of risk factors, or under-reporting of high-risk behaviour. Efforts are needed to better understand these differences and to quantify infectivity in low-income countries.
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            Probability of HIV-1 transmission per coital act in monogamous, heterosexual, HIV-1-discordant couples in Rakai, Uganda.

             T VanCott,  ,  Xiaohui Li (2001)
            The probability of HIV-1 transmission per coital act in representative African populations is unknown. We aimed to calculate this probability overall, and to estimate how it is affected by various factors thought to influence infectivity. 174 monogamous couples, in which one partner was HIV-1 positive, were retrospectively identified from a population cohort in Rakai, Uganda. Frequency of intercourse and reliability of reporting within couples was assessed prospectively. HIV-1 seroconversion was determined in the uninfected partners, and HIV-1 viral load was measured in the infected partners. Adjusted rate ratios of transmission per coital act were estimated by Poisson regression. Probabilities of transmission per act were estimated by log-log binomial regression for quartiles of age and HIV-1 viral load, and for symptoms or diagnoses of sexually transmitted diseases (STDs) in the HIV-1-infected partners. The mean frequency of intercourse was 8.9 per month, which declined with age and HIV-1 viral load. Members of couples reported similar frequencies of intercourse. The overall unadjusted probability of HIV-1 transmission per coital act was 0.0011 (95% CI 0.0008-0.0015). Transmission probabilities increased from 0.0001 per act at viral loads of less than 1700 copies/mL to 0.0023 per act at 38 500 copies/mL or more (p=0.002), and were 0.0041 with genital ulceration versus 0.0011 without (p=0.02). Transmission probabilities per act did not differ significantly by HIV-1 subtypes A and D, sex, STDs, or symptoms of discharge or dysuria in the HIV-1-positive partner. Higher viral load and genital ulceration are the main determinants of HIV-1 transmission per coital act in this Ugandan population.
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              • Article: not found

              From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection

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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                bwho
                Bulletin of the World Health Organization
                Bull World Health Organ
                World Health Organization (Genebra )
                0042-9686
                November 2012
                : 90
                : 11
                : 831-838A
                Affiliations
                [1 ] Imperial College London United Kingdom
                [2 ] UNITAID Switzerland
                [3 ] Weill Cornell Medical College Qatar Qatar
                Article
                S0042-96862012001100012
                10.2471/BLT.12.102574
                3506404
                23226895

                http://creativecommons.org/licenses/by/4.0/

                Product
                Product Information: SciELO Public Health
                Categories
                Health Policy & Services

                Public health

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