Social Network Clustering and the Spread of HIV/AIDS Among Persons Who Inject Drugs in 2 Cities in the Philippines

Abstract

INTRODUCTION The Philippines has seen rapid increases in HIV prevalence among people who inject drugs. We study two neighboring cities where a linked HIV epidemic differed in timing of onset and levels of prevalence. In Cebu, prevalence rose rapidly from under 1% to 54% between 2009 and 2011 and remained high through 2013. In nearby Mandaue, HIV remained below 4% through 2011 then rose rapidly to 38% by 2013. OBJECTIVES We hypothesize that infection prevalence differences in these cities may owe to aspects of social network structure, specifically levels of network clustering. Building on prior research, we hypothesize that higher levels of network clustering are associated with greater epidemic potential. METHODS Data were collected with respondent-driven sampling among males who inject drugs in Cebu and Mandaue in 2013. We first examine sample composition using estimators for population means. We then apply new estimators of network clustering in respondent-driven sampling data to examine associations with HIV prevalence. RESULTS Samples in both cities were comparable in terms of composition by age, education, and injection locations. Dyadic needle sharing levels were also similar between the two cities, but network clustering in the needle sharing network differed dramatically. We found higher clustering in Cebu than Mandaue, consistent with expectations that higher clustering is associated with faster epidemic spread. CONCLUSION This paper is the first to apply estimators of network clustering to empirical respondent-driven samples, and it offers suggestive evidence that researchers should pay greater attention to network structure’s role in HIV transmission dynamics.

Trends and emerging directions in HIV risk and prevention research in the Philippines: A systematic review of the literature

“…Ten articles reporting data from 9 independent studies reported prevalence of HIV-positive status [13,20,21,23,24,31,34,39,58,59]. HIV prevalence across studies ranged from 0% (in 3 independent studies of 560 female and male adults in Cebu [13], 62 blood donor samples from Manila [20], and 100 incarcerated females in Manila [31]) to 52.0% in a sample of 457 participants in Cebu who were recruited using respondent driven sampling [34].…”

Racial Inequities in HIV Prevalence and Composition of Risk Networks Among People Who Inject Drugs in HIV Prevention Trial Network 037

“…Recent studies of PWID done in India and the Philippines have evaluated network composition and its relationship with HIV risk and found that larger networks and network clustering were significantly associated with HIV transmission. 20,21 Although these studies did not particularly address issues related to racial/ethnic inequities in HIV incidence, they show the importance of considering network composition when evaluating HIV risk and building prevention strategies. In the United States, the majority of network studies have been done among heterosexual and men who have sex with men (MSM) populations and show, as we found in our study, that risk behaviors tend to be lower and racial homophily higher among blacks.…”

One-step estimation of networked population size: Respondent-driven capture-recapture with anonymity

“…Beyond the oversampling of high degree nodes, RDS faces challenges when used in networks where network clustering is pronounced [ 49 , 87 ]. While methods are available to assess the presence of clustering [ 25 ], and recent work has proposed new techniques to estimate and account for clustering from a single RDS sample [ 88 ], the effects of this phenomenon on population size estimation from RDS samples is seldom discussed. The root of the problem lies in the fact that RDS walks necessarily sample network neighborhoods.…”