Social network-based recruitment successfully reveals HIV-1 transmission networks among high-risk individuals in El Salvador.
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.
Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC 27599-7030, USA. adennis@med.unc.edu
Ann M
AM
Dennis
Wendy
W
Murillo
Flor
F
de Maria Hernandez
Maria Elena
ME
Guardado
Ana Isabel
AI
Nieto
Ivette
I
Lorenzana de Rivera
Joseph J
JJ
Eron
Gabriela
G
Paz-Bailey
D004544:El Salvador; D004812:Epidemiologic Methods; D005260:Female; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission* / Q000821:virology; D015497:HIV-1 / Q000235:genetics*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D015995:Prevalence; D012306:Risk; D012494:Sampling Studies; D017422:Sequence Analysis, DNA; D060386:Sex Workers; D012944:Social Support