Faculty Bibliography

The concept of the "risk environment"--defined as the "space ... [where] factors exogenous to the individual interact to increase the chances of HIV transmission"--draws together the disciplines of public health and geography. Researchers have increasingly turned to geographic methods to quantify dimensions of the risk environment that are both structural and spatial (e.g., local poverty rates). The scientific power of the intersection between public health and geography, however, has yet to be fully mined. In particular, research on the risk environment has rarely applied geographic methods to create neighbourhood-based measures of syringe exchange programmes (SEPs) or of drug-related law enforcement activities, despite the fact that these interventions are widely conceptualized as structural and spatial in nature and are two of the most well-established dimensions of the risk environment. To strengthen research on the risk environment, this paper presents a way of using geographic methods to create neighbourhood-based measures of (1) access to SEP sites and (2) exposure to drug-related arrests, and then applies these methods to one setting (New York City [NYC]). NYC-based results identified substantial cross-neighbourhood variation in SEP site access and in exposure to drug-related arrest rates (even within the subset of neighbourhoods nominally experiencing the same drug-related police strategy). These geographic measures--grounded as they are in conceptualizations of SEPs and drug-related law enforcement strategies--can help develop new arenas of inquiry regarding the impact of these two dimensions of the risk environment on injectors' health, including exploring whether and how neighbourhood-level access to SEP sites and exposure to drug-related arrests shape a range of outcomes among local injectors.

Political-economic transitions in the Soviet Union, Indonesia, and China, but not the Philippines, were followed by HIV epidemics among drug users. Wars also may sometimes increase HIV risk. Based on similarities in some of the causal pathways through which wars and transitions can affect HIV risk, we use the term "Big Events" to include both. We first critique several prior epidemiological models of Big Events as inadequately incorporating social agency and as somewhat imprecise and over-generalizing in their sociology. We then suggest a model using the following concepts: first, event-specific HIV transmission probabilities are functions of (a) the probability that partners are infection-discordant; (b) the infection-susceptibility of the uninfected partner; (c) the infectivity of the infected--as well as (d) the behaviours engaged in. These probabilities depend on the distributions of HIV and other variables in populations. Sexual or injection events incorporate risk behaviours and are embedded in sexual and injection partnership patterns and community networks, which in turn are shaped by the content of normative regulation in communities. Wars and transitions can change socio-economic variables that can sometimes precipitate increases in the numbers of people who engage in high-risk drug and sexual networks and behaviours and in the riskiness of what they do. These variables that Big Events affect may include population displacement; economic difficulties and policies; police corruption, repressiveness, and failure to preserve order; health services; migration; social movements; gender roles; and inter-communal violence--which, in turn, affect normative regulation, youth alienation, networks and behaviours. As part of these pathways, autonomous action by neighbourhood residents, teenagers, drug users and sex workers to maintain their economic welfare, health or happiness may affect many of these variables or otherwise mediate whether HIV epidemics follow transitions. We thus posit that research on whether and how these interacting causal pathways and autonomous actions are followed by drug-related harm and/or HIV or other epidemics can help us understand how to intervene to prevent or mitigate such harms.

OBJECTIVE: To explore the potential utility of hepatitis C virus (HCV) seroprevalence as a biomarker for injection risk, and herpes simplex virus-2 (HSV-2) as a biomarker for sexual risk among injecting drug users (IDUs). We examined the relationships between HCV and HIV and between HSV-2 and HIV among injecting drug users in New York City relative to the large-scale implementation of syringe exchange in the mid-1990s. METHODS: 397 injecting drug users were recruited from a drug detoxification program in New York from 2005 to 2007. Informed consent was obtained, a questionnaire covering demographics, drug use and HIV risk was administered. Blood samples were tested for antibody to HIV, HCV and HSV-2. RESULTS: Among all subjects, HIV prevalence was 17%, HCV prevalence 72% and HSV-2 prevalence 48%. Among IDUs who began injecting before 1995, HIV was 28%, HCV serostatus was strongly associated with HIV serostatus (AOR=8.96, 95% CI 1.16-69.04) and HSV-2 serostatus was not associated with HIV serostatus (AOR=1.31, 95% CI 0.64-2.67). Among subjects who began injecting in 1995 or later, HIV was 6%, HCV was not associated with HIV (AOR=1.04, 95% CI 0.27-4.08) and HSV-2 serostatus was strongly related to HIV serostatus (AOR=10.71, 95% CI 1.18-97.57). CONCLUSIONS: HCV and HSV-2 HCV and HSV-2 may provide important new tools for monitoring evolving HIV epidemics among IDUs. Reconsideration of the current CDC hierarchical transmission risk classification system may also be warranted.

This research presents estimates of HIV prevalence rates among injection drug users (IDUs) in large US metropolitan statistical areas (MSAs) during 1992-2002. Trend data on HIV prevalence rates in geographic areas over time are important for research on determinants of changes in HIV among IDUs. Such data also provide a foundation for the design and implementation of structural interventions for preventing the spread of HIV among IDUs. Our estimates of HIV prevalence rates among IDUs in 96 US MSAs during 1992-2002 are derived from four independent sets of data: (1) research-based HIV prevalence rate estimates; (2) Centers for Disease Control and Prevention Voluntary HIV Counseling and Testing data (CDC CTS); (3) data on the number of people living with AIDS compiled by the CDC (PLWAs); and (4) estimates of HIV prevalence in the US. From these, we calculated two independent sets of estimates: (1) calculating CTS-based Method (CBM) using regression adjustments to CDC CTS; and (2) calculating the PLWA-based Method (PBM) by taking the ratio of the number of injectors living with HIV to the numbers of injectors living in the MSA. We take the mean of CBM and PBM to calculate over all HIV prevalence rates for 1992-2002. We evaluated trends in IDU HIV prevalence rates by calculating estimated annual percentage changes (EAPCs) for each MSA. During 1992-2002, HIV prevalence rates declined in 85 (88.5%) of the 96 MSAs, with EAPCs ranging from -12.9% to -2.1% (mean EAPC=-6.5%; p<0.01). Across the 96 MSAs, collectively, the annual mean HIV prevalence rate declined from 11.2% in 1992 to 6.2 in 2002 (EAPC, -6.4%; p<0.01). Similarly, the median HIV prevalence rate declined from 8.1% to 4.4% (EAPC, -6.5%; p<0.01). The maximum HIV prevalence rate across the 11 years declined from 43.5% to 22.8% (EAPC, -6.7%; p<0.01). Declining HIV prevalence rates may reflect high continuing mortality among infected IDUs, as well as primary HIV prevention for non-infected IDUs and self-protection efforts by them. These results warrant further research into the population dynamics of disease progression, access to health services, and the effects of HIV prevention interventions for IDUs.

OBJECTIVES/OBJECTIVE:To describe: (a) the prevalence and individual and network characteristics of group sex events (GSEs) and GSE attendees; and (b) HIV/sexually transmitted infection (STI) discordance among respondents who said they went to a GSE together. METHODS AND DESIGN/METHODS:In a sociometric network study of risk partners (defined as sexual partners, persons with whom respondents attended a GSE, or drug injection partners) in Brooklyn, NY, we recruited a high-risk sample of 465 adults. Respondents reported on GSE attendance, the characteristics of GSEs, and their own and others' behaviors at GSEs. Sera and urines were collected, and STI prevalence was assayed. RESULTS:Of the 465 participants, 36% had attended a GSE in the last year, 26% had sex during the most recent of these GSEs, and 13% had unprotected sex there. Certain subgroups (hard drug users, men who have sex with men, women who have sex with women, and sex workers) were more likely to attend and more likely to engage in risk behaviors at these events. Among 90 GSE dyads, in which at least 1 partner named the other as someone with whom they attended a GSE in the previous 3 months, STI/HIV discordance was common [herpes simplex virus (HSV-2): 45% of dyads, HIV: 12% of dyads, and chlamydia: 21% of dyads]. Many GSEs had 10 or more participants, and multiple partnerships at GSEs were common. High attendance rates at GSEs among members of large networks may increase community vulnerability to STI/HIV, particularly because network data show that almost all members ofa large sociometric risk network either had sex with a GSE attendee or had sex with someone who had sex with a GSE attended. CONCLUSIONS:Self-reported GSE attendance and participation were common among this high-risk sample. STI/HIV discordance among GSE attendees was high, highlighting the potential transmission risk associated with GSEs. Research on sexual behaviors should incorporate measures of GSE behaviors as standard research protocol. Interventions should be developed to reduce transmission at GSEs.