Social NetworkBased Recruitment Successfully Reveals HIV-1 Transmission Networks Among High-Risk Individuals in El Salvador

Dennis, Ann M. MD*; Murillo, Wendy PhD; de Maria Hernandez, Flor MD, MPH; Guardado, Maria Elena MD, MPH§; Nieto, Ana Isabel MD; Lorenzana de Rivera, Ivette MS; Eron, Joseph J. MD*; Paz-Bailey, Gabriela MD, MSc, PhD‡,§

JAIDS Journal of Acquired Immune Deficiency Syndromes:
doi: 10.1097/QAI.0b013e318288b246
Epidemiology and Prevention

Objective: HIV in Central America is concentrated among certain groups such as men who have sex with men (MSM) and female sex workers (FSWs). We compared social recruitment chains and HIV transmission clusters from 699 MSM and 787 FSWs to better understand factors contributing to ongoing HIV transmission in El Salvador.

Methods: Phylogenies were reconstructed using pol sequences from 119 HIV-positive individuals recruited by respondent-driven sampling (RDS) and compared with RDS chains in 3 cities in El Salvador. Transmission clusters with a mean pairwise genetic distance ≤0.015 and Bayesian posterior probabilities =1 were identified. Factors associated with cluster membership were evaluated among MSM.

Results: Sequences from 34 (43%) MSM and 4 (10%) FSW grouped in 14 transmission clusters. Clusters were defined by risk group (12 MSM clusters) and geographic residence (only 1 spanned separate cities). In 4 MSM clusters (all n = 2), individuals were also members of the same RDS chain, but only 2 had members directly linked through recruitment. All large clusters (n ≥ 3) spanned >1 RDS chain. Among MSM, factors independently associated with cluster membership included recent infection by BED assay (P = 0.02), sex with stable male partners (P = 0.02), and sex with ≥3 male partners in the past year (P = 0.04).

Conclusions: We found few HIV transmissions corresponding directly with the social recruitment. However, we identified clustering in nearly one-half of MSM suggesting that RDS recruitment was indirectly but successfully uncovering transmission networks, particularly among recent infections. Interrogating RDS chains with phylogenetic analyses may help refine methods for identifying transmission clusters.

Author Information

*Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC;

Department of Microbiology, National Autonomous University of Honduras, Tegucigalpa, Honduras;

Center for Health Studies - HIV Surveillance, Del Valle University of Guatemala, Guatemala City, Guatemala;

§Tephinet, Inc, Atlanta, GA; and

National HIV Program, Ministry of Health, San Salvador, El Salvador.

Correspondence to: Ann M. Dennis, Division of Infectious Diseases, 130 Mason Farm Road, Suite 2115, CB# 7030, Chapel Hill, NC 27599-7030 (e-mail:

Supported by the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant KL2TR000084, Sida/SAREC on behalf of a bilateral collaboration with the National Autonomous University of Honduras, the Network for Research and Training in Tropical Diseases in Central America (NeTropica) under the project No 06-R-2010, the Training Programs in Epidemiology and Public Health Interventions Network (TEPHINET) through a cooperative agreement (#6D43GH000014-05) from the Centers for Disease Control and Prevention (CDC) and the United States Agency for International Development (USAID).

Parts of this work were presented at the 19th Conference on Retroviruses and Opportunistic Infections (CROI), March 2012, Seattle, WA (Abstract #F-148).

The authors have no conflicts of interest to disclose.

Received September 05, 2012

Accepted January 18, 2013

© 2013 Lippincott Williams & Wilkins, Inc.