Estimating HIV incidence using the model modes of transmission for concentrated epidemics: Peru 2009
J. Alarcón1, M. Pun2, C. Gutiérrez1, A. Wittembury2, R. Tejada1, L. Suárez2, G. Rosell3, A. Bórquez4, P. Cuchi5
1Instituto de Medicina Tropical, UNMSM, Lima, Peru, 2Dirección General de Epidemiología, Ministerio de Salud, Lima, Peru, 3Estrategia Sanitaria Nacional de Prevención y Control de VIH-SIDA, MOH, Lima, Peru, 4Imperial Collage London, London, United Kingdom, 5UNAIDS, Geneva, Switzerland
Background: Peru's HIV surveillance system, initiated in 1989, has generated a lot of HIV prevalence data, including on specific populations groups. However, information on HIV incidence is scarce. Yet, an understanding of the number and distribution of new HIV infections is key to prevention planning. This study applied the UNAIDS HIV incidence model by modes of transmission (MoT) to estimate the distribution of incident HIV infections in Peru for 2010 by transmission category.
Methods: The MoT model used data on population sizes, HIV and STI prevalence, and risk behaviors in the 15-49 years old population. The data was gathered from technical reports, official statistics, national surveys, and scientific publications. After inputting the data and a consultation with experts, adjustments and uncertainty analysis were performed.
Results: The model estimated the 2009 national prevalence at 0.45% and the annual incidence for 2010 at 0.03%. Of the estimated 4,346 new infections in 2010, 55% (35%-65%) are among MSM, and 43% among heterosexuals infected through sex. The latter includes: “low-risk heterosexual population” (16%), female partners of high risk groups (12.8%), heterosexuals having casual sex and their partners (12%) and other heterosexual groups not using injecting drugs (2%). The model calculated that around 797 incident cases will occur in partners (female and male) of individual in the high risk groups (18%).
Conclusions: The model provided a good estimation of incidence and its distribution among the risk groups by mode of transmission, consistent with distributions of HIV case reports. A limitation in the current version is that it doesn't account for different risk levels within population groups, i.e. MSM. The model allows creating scenarios to help decision making and policy formulation, surveillance and planning for prevention and control.
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