HIV Infection among Young People in Northwest Tanzania: The Role of Biological, Behavioural and Socio- Demographic Risk Factors Francesca Lemme 1,2 , Aoife M. Doyle 1,2 , John Changalucha 3 , Aura Andreasen 1,2 , Kathy Baisley 1 , Kaballa Maganja 2 , Deborah Watson-Jones 1,2 , Saidi Kapiga 1,2 , Richard J. Hayes 1 , David A. Ross 1 * 1 London School of Hygiene and Tropical Medicine, London, United Kingdom, 2 Mwanza Intervention Trials Unit, National Institute for Medical Research, Mwanza, Tanzania, 3 National Institute for Medical Research, Mwanza, Tanzania Abstract Background: Young people are at high risk of HIV and developing appropriate prevention programmes requires an understanding of the risk factors for HIV in this age group. We investigated factors associated with HIV among participants aged 15–30 years in a 2007–8 cross-sectional survey nested within a community-randomised trial of the MEMA kwa Vijana intervention in 20 rural communities in northwest Tanzania. Methods: We analysed data for 7259(53%) males and 6476(47%) females. Using a proximate-determinant conceptual framework and conditional logistic regression, we obtained sex-specific Odds Ratios (ORs) for the association of HIV infection with socio-demographic, knowledge, behavioural and biological factors. Results: HSV-2 infection was strongly associated with HIV infection (females: adjOR 4.4, 95%CI 3.2–6.1; males: adjOR 4.2, 95%CI 2.8–6.2). Several socio-demographic factors (such as age, marital status and mobility), behavioural factors (condom use, number and type of sexual partnerships) and biological factors (blood transfusion, lifetime pregnancies, genital ulcers, Neisseria gonorrhoeae) were also associated with HIV infection. Among females, lifetime sexual partners (linear trend, p,0.001), $2 partners in the past year (adjOR 2.0, 95%CI 1.4–2.8), $2 new partners in the past year (adjOR 1.9 95%CI 1.2, 3.3) and concurrent partners in the past year (adjOR 1.6 95%CI 1.1, 2.4) were all associated with HIV infection. Conclusions: Efforts must be intensified to find effective interventions to reduce HSV-2. Effective behavioural interventions focusing on reducing the number of sexual partnerships and risk behaviour within partnerships are also needed. An increase in risky sexual behaviour may occur following marriage dissolution or when a young woman travels outside of her community and interventions addressing the needs of these subgroups of vulnerable women may be important. Trial Registration: ClinicalTrial.gov NCT00248469. Citation: Lemme F, Doyle AM, Changalucha J, Andreasen A, Baisley K, et al. (2013) HIV Infection among Young People in Northwest Tanzania: The Role of Biological, Behavioural and Socio-Demographic Risk Factors. PLoS ONE 8(6): e66287. doi:10.1371/journal.pone.0066287 Editor: Patrick S. Sullivan, Rollins School of Public Health, Emory University, United States of America Received November 8, 2012; Accepted May 5, 2013; Published June 21, 2013 Copyright: ß 2013 Lemme et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded through grants from the European Commission, and the United Kingdom Department for International Development and Irish Aid. Additional funding was received from the Medical Research Council of Great Britain and The United Nations Joint Programme on HIV/AIDS (UNAIDS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: ross@lshtm.ac.uk Introduction Young people aged 15–24 years account for an estimated 40% of new adult HIV infections worldwide [1]. The United Nations General Assembly Special Session on HIV/AIDS (UNGASS) Declaration of Commitment established a target to reduce HIV prevalence by 25% in young people aged 15–24 in the most affected countries by 2005 [2]. HIV prevalence has declined among young people since 2000–2001 in 16 of the 21 high prevalence countries with sufficient data, including Tanzania. However, significant declines of 25% were seen in only ten of these countries [3]. Effective HIV prevention in young people therefore remains an urgent priority, but the design of HIV prevention interventions requires a clear understanding of the social, behavioural and biological factors that influence the risk of HIV infection. Previous studies in Tanzania and elsewhere have identified a number of factors that are commonly associated with increased risk of HIV infection such as age [4,5,6], socio-economic status [4,7,8], educational status [9,10]; marital status [4,6,9,10], mobility [6,11], high risk sexual behaviours [4,5,6,10] and co- infection with other sexually transmitted infections (STIs) [6,9,12,13,14]. However, the relative contribution of these factors varies between locations and also can vary over time as the epidemic matures and prevention efforts intensify [7,8]. The majority of these studies were carried out in the late 1990’s and early 2000’s and few focused specifically on young people. Between 1998 and 2008 a community-randomised controlled trial PLOS ONE | www.plosone.org 1 June 2013 | Volume 8 | Issue 6 | e66287