Assessing Individual and Disseminated Effects in Network-Randomized Studies

Implementation trials often involve clustering via risk networks, where only some participants directly receive the intervention. The individual effect is that among directly treated persons beyond being in an intervention network; the disseminated effect is that among persons engaged with those directly treated. In this article, we employ a causal inference framework and discuss assumptions and estimators for individual and disseminated effects and apply them to the HIV Prevention Trials Network 037 Study. HIV Prevention Trials Network 037 was a phase III, network-level, randomized controlled human immunodeficiency virus (HIV) prevention trial conducted in the United States and Thailand from 2002 to 2006 that recruited injection drug users, who were assigned to either an intervention group or a control group, and their risk network members, who received no direct intervention. Combining individual and disseminated effects, we observed a 35% composite rate reduction in the adjusted model (risk ratio = 0.65, 95% confidence interval: 0.47, 0.90). Methodology is now available for estimating the full set of these effects, enhancing knowledge gained from network-randomized trials. Although the overall effect gains validity from network randomization, we show that it will generally be less than the composite effect. Additionally, if only index participants benefit from the intervention, as the network size increases, the overall effect tends toward the null-an unfortunate and misleading conclusion.

Pockets of HIV Non-infection Within Highly-Infected Risk Networks in Athens, Greece

As part of a network study of HIV infection among people who inject drugs (PWID) and their contacts, we discovered a connected subcomponent of 29 uninfected PWID. In the context of a just-declining large epidemic outbreak, this raised a question: What explains the existence of large pockets of uninfected people? Possible explanations include “firewall effects” (Friedman et al., 2000; Dombrowski et al., 2017) wherein the only HIV+ people that the uninfected take risks with have low viral loads; “bottleneck effects” wherein few network paths into the pocket of non-infection exist; low levels of risk behavior; and an impending outbreak. We considered each of these. Participants provided information on their enhanced sexual and injection networks and assisted us in recruiting network members. The largest connected component had 241 members. Data on risk behaviors in the last 6 months were collected at the individual level. Recent infection was determined by LAg (Sedia^TM Biosciences Corporation), data on recent seronegative tests, and viral load. HIV RNA was quantified using Artus HI Virus-1 RG RT-PCR (Qiagen). The 29 members of the connected subcomponent of uninfected participants were connected (network distance = 1) to 17 recently-infected and 24 long-term infected participants. Fourteen (48%) of these 29 uninfected were classified as “extremely high risk” because they self-reported syringe sharing and had at least one injection partner with viral load >100,000 copies/mL who also reported syringe sharing. Seventeen of the 29 uninfected were re-interviewed after 6 months, but none had seroconverted. These findings show the power of network research in discovering infection patterns that standard individual-level studies cannot. Theoretical development and exploratory network research studies may be needed to understand these findings and deepen our understanding of how HIV does and does not spread through communities. Finally, the methods developed here provide practical tools to study “bottleneck” and “firewall” network hypotheses in practice.

Change and variability in drug treatment coverage among people who inject drugs in 90 large metropolitan areas in the USA, 1993-2007

BACKGROUND

Our previous research has found low and stable mean drug treatment coverage among people who inject drugs (PWID) across 90 large US metropolitan statistical areas (MSAs) during 1993-2002. This manuscript updates previous estimates of change in drug treatment coverage for PWID in 90 MSAs during 1993-2007.

METHODS

Our drug treatment sample for calculating treatment coverage includes clients enrolled in residential or ambulatory inpatient/outpatient care, detoxification services, and methadone maintenance therapy at publicly- and privately-funded substance abuse agencies receiving public funds. Coverage was measured as the number of PWID in drug treatment, calculated by using data from the Substance Abuse and Mental Health Service Administration, divided by numbers of PWID in each MSA. We modeled change in drug treatment coverage rates using a negative binomial mixed-effects model. Fixed-effects included an intercept and a main effect for time. Incidence rate ratios (IRR) were calculated for both average change from 1993 to 2007 and MSA-specific estimates of change in coverage rates.

RESULTS

On average over all MSAs, coverage was low in 1993 (6.1%) and showed no improvement from 1993 to 2007 (IRR = 0.99; 95% CI, 0.86, 1.2). There was modest variability across MSAs in coverage in 1993 (log incidence rate SD = 0.36) as well as in coverage change from 1993 to 2007 (log IRR SD = 0.32). In addition, results indicate significant variability among MSAs in coverage.

CONCLUSIONS

Inadequate treatment coverage for PWID may produce a high cost to society in terms of the spread of overdose mortality and injection-related infectious diseases. A greater investment in treatment will likely be needed to have a substantial and more consistent impact on injection drug use-related harms. Future research should examine MSA-level predictors associated with variability in drug treatment coverage.

Dissolution of Committed Partnerships during Incarceration and STI/HIV-Related Sexual Risk Behavior after Prison Release among African American Men

Incarceration is strongly associated with post-release STI/HIV risk. One pathway linking incarceration and STI/HIV risk may be incarceration-related dissolution of protective network ties. Among African American men released from prison who were in committed partnerships with women at the time of incarceration (N = 207), we measured the association between committed partnership dissolution during incarceration and STI/HIV risk in the 4 weeks after release. Over one-quarter (28%) experienced incarceration-related partnership dissolution. In adjusted analyses, incarceration-related partnership dissolution was strongly associated with post-release binge drinking (adjusted odds ratio (AOR) 4.2, 95% confidence interval (CI); 1.4-15.5). Those who experienced incarceration-related partnership dissolution were much more likely to engage in multiple/concurrent partnerships or sex trade defined as buying or selling sex (64%) than those who returned to the partner (12%; AOR 20.1, 95% CI 3.4-175.6). Policies that promote maintenance of relationships during incarceration may be important for protecting health.

Young Drug Users: a Vulnerable Population and an Underutilized Resource in HIV/HCV Prevention

PURPOSE OF REVIEW

The social networks of people who inject drugs (PWID) have long been studied to understand disease transmission dynamics and social influences on risky practices. We illustrate how PWID can be active agents promoting HIV, HCV, and overdose prevention.

RECENT FINDINGS

We assessed drug users' connections and interactions with others at risk for HIV/HCV in three cities: New York City (NYC), USA (n = 539); Pereira, Colombia (n = 50); and St. Petersburg, Russia (n = 49). In all three cities, the majority of participants' network members were of a similar age as themselves, yet connections across age groups were also present. In NYC, knowing any opioid user(s) older than 29 was associated with testing HCV-positive. In NYC and St. Petersburg, a large proportion of PWID engaged in intravention activities to support safer injection and overdose prevention; in Pereira, PWID injected, had sex, and interacted with other key groups at risk. People who use drugs can be active players in HIV/HCV and overdose risk- reduction; their networks provide them with ample opportunities to disseminate harm reduction knowledge, strategies, and norms to others at risk. Local communities could augment prevention programming by empowering drug users to be allies in the fight against HIV and facilitating their pre-existing health-protective actions.

Molecular Tracing of the Geographical Origin of Human Immunodeficiency Virus Type 1 Infection and Patterns of Epidemic Spread Among Migrants Who Inject Drugs in Athens

Background

High numbers of human immunodeficiency virus type 1 (HIV-1) infections among people who inject drugs (PWID) have been diagnosed in Athens, Greece, since 2011. We aimed to trace the geographic origin of HIV-1 infection for migrants who inject drugs and to investigate whether transmissions occur more frequently among migrants than among Greek nationals.

Methods

Multiple cross-sectional studies were pooled to assemble all persons diagnosed with HIV-1 in Greece between 1 January 2011 and 31 October 2014. Phylogenetic analyses used maximum likelihood estimation. The hypothesis of ethnic compartmentalization was tested by reconstructing ancestral states of characters at the tips using the criterion of parsimony over a set of bootstrap trees.

Results

Of 2274 persons, 38.4% were PWID. Phylogenetic analyses showed the existence of 4 major PWID-specific local transmission networks (LTNs): CRF14_BG (437 [58.6%]), CRF35_AD (139 [18.6%]), subtype B (116 [15.6%]), and subtype A (54 [7.2%]). Of 184 non-Greek PWID, 78.3% had been infected within the PWID-LTNs. For 173 (94.3%), the origin of their infection was assumed to be in Greece (postmigration). For PWID infected within LTNs, transmissions for subtype A and CRF14_BG occurred more frequently among migrants than would be expected by chance (phyloethnic study).

Conclusions

Our analysis showed that the majority of infections among migrants occurred postmigration. The existence of significant transmission networking among migrants highlights that this population is a priority for HIV prevention. As molecular analysis can estimate the probable country of HIV infection, it can help to inform the design of public health strategies.

Molecular Analysis of Human Immunodeficiency Virus Type 1 (HIV-1)-Infected Individuals in a Network-Based Intervention (Transmission Reduction Intervention Project): Phylogenetics Identify HIV-1-Infected Individuals With Social Links

Background

The Transmission Reduction Intervention Project (TRIP) is a network-based intervention that aims at decreasing human immunodeficiency virus type 1 (HIV-1) spread. We herein explore associations between transmission links as estimated by phylogenetic analyses, and social network-based ties among persons who inject drugs (PWID) recruited in TRIP.

Methods

Phylogenetic trees were inferred from HIV-1 sequences of TRIP participants. Highly supported phylogenetic clusters (transmission clusters) were those fulfilling 3 different phylogenetic confidence criteria. Social network-based ties (injecting or sexual partners, same venue engagement) were determined based on personal interviews, recruitment links, and field observation.

Results

TRIP recruited 356 individuals (90.2% PWID) including HIV-negative controls; recently HIV-infected seeds; long-term HIV-infected seeds; and their social network members. Of the 150 HIV-infected participants, 118 (78.7%) were phylogenetically analyzed. Phylogenetic analyses suggested the existence of 13 transmission clusters with 32 sequences. Seven of these clusters included 14 individuals (14/32 [43.8%]) who also had social ties with at least 1 member of their cluster. This proportion was significantly higher than what was expected by chance.

Conclusions

Molecular methods can identify HIV-infected people socially linked with another person in about half of the phylogenetic clusters. This could help public health efforts to locate individuals in networks with high transmission rates.

Network Research Experiences in New York and Eastern Europe: Lessons for the Southern US in Understanding HIV Transmission Dynamics

PURPOSE

This paper presents an overview of different kinds of risk and social network methods and the kinds of research questions each can address.

RECENT FINDINGS

It also reviews what network research has discovered about how network characteristics are associated with HIV and other infections, risk behaviors, preventive behaviors, and care, and discusses some ways in which network-based public health interventions have been conducted. Based on this, risk and social network research and interventions seem both feasible and valuable for addressing the many public health and social problems raised by the widespread use of opioids in the US South.

Engagement in sex work does not increase HIV risk for women who inject drugs in Ukraine

Background

We studied the association between sex in exchange for money, drugs or goods and HIV for women who inject drugs (WWID) in Ukraine, as previous data on this association from the post-USSR region are contradictory.

Methods

Data come from the Integrated Bio-Behavioral Survey of Ukrainian people who inject drugs collected in 2011 using respondent-driven sampling. Participants were interviewed and tested with rapid HIV tests.

Results

The sample included 2465 WWID (24% HIV positive); 214 (8.7%) of which reported having had exchange sex during the last 90 days. Crude analysis showed no association between exchange sex and HIV (OR = 0.644; 95% CI 0.385–1.077). No confounders were found to alter this result in a multivariable analysis. Further modeling showed that exchange sex modifies association between HIV and alcohol use: no association between HIV and daily alcohol use was found for those women who exchanged sex (OR = 1.699, 95% CI 0.737–3.956); while not engaging in sex work and daily using alcohol reduced odds to be HIV infected (OR = 0.586, 95% CI 0.389–0.885).

Conclusions

Exchange sex may have less impact on the HIV status of WWID who are exposed to injecting risks. The finding that daily alcohol use appears protective against HIV among WWID who do not exchange sex requires more research.

Molecular investigation of HIV-1 cross-group transmissions during an outbreak among people who inject drugs (2011-2014) in Athens, Greece

New diagnoses of HIV-1 infection among people who inject drugs (PWID) rocketed in Athens, Greece between 2011 and 2014 (HIV-1 outbreak). Our aim was to identify, during that period, potential cross-group transmissions between the within-Greece PWID and other risk or national groups using molecular methods. Sequences from 33 PWID were outside the PWID-outbreak networks in Greece (PWID-imported transmissions). Phylogenetic analyses on 28 of these sequences (subtypes A and B) showed that 11 subtype B infections originated from Greece, whereas 8 and 7 subtype A strains were from former Soviet Union countries (A_FSU) and Greece, respectively. The putative source in half of the PWID-imported transmissions with Greek origin was an individual who acquired HIV via sexual contact. During four years of an HIV-1 outbreak among PWID in Athens, Greece, 33 individuals in this group (4.6% of all diagnoses with phylogenetic analyses) are likely to represent infections, sexually or injection-acquired, outside the within-Greece-PWID-outbreak networks. Combined molecular and traditional HIV surveillance to monitor introductions of new strains, and interventions that aim at reducing the rate of both injection and sexual risky practices are needed during drug injection-related HIV outbreaks.

A Qualitative Investigation Comparing Psychosocial and Physical Sexual Experiences Related to Alcohol and Marijuana Use among Adults

Alcohol and marijuana are two of the most prevalent psychoactive substances and each may result in distinct psychosocial and physical sexual experiences and different sexual risk behaviors. With marijuana becoming more accepted in the US along with more liberal state-level policies, it is important to examine and compare users' psychosocial and physical sexual experiences and sexual risk behavior associated with these drugs. In this study, we interviewed 24 adults who recently used marijuana before sex. Participants were 50 % female and all self-identified as heterosexual and HIV-negative. Using thematic analysis, we compared self-reported psychosocial and physical sexual experiences of alcohol and marijuana. Participants described differences between drugs with regard to psychosocial (e.g., partner interactions and contexts before sex, partner choice, perceived attractiveness of self and others, disinhibition, and feelings of regret after sex) and physical sexual experiences (e.g., sexual dysfunction, dose effects, sensations of body/sex organs, length and intensity of sex, and orgasm). Alcohol use was commonly associated with social outgoingness and use facilitated connections with potential sexual partners; however, alcohol was more likely than marijuana to lead to atypical partner choice or post-sex regret. Both alcohol and marijuana had a variety of negative sexual effects, and the illegality of marijuana reportedly facilitated intimate encounters. While sexual experiences tended to be similar across males and females, we did find some variation by gender. Results can inform prevention and harm reduction programming that will allow us to design more realistic programs and to craft interventions, which guide potential users to make safer choices.

Network Viral Load: A Critical Metric for HIV Elimination

BACKGROUND

Associations have been observed between an aggregate viral load measure, the community viral load, and new HIV diagnoses. The community viral load aggregates viral loads within chosen geographic areas, restricting inferences about HIV acquisition risk to these areas. We develop a more precise metric, the network viral load (NVL), to measure the composite viral load within a risk network of a HIV-negative individual.

METHODS

We examined the relationship between NVL and HIV infection among young men who have sex with men in Chicago, United States. Networks were generated using respondent-driven sampling. NVL was defined as the prevalence of viremic individuals in one's risk network, characterized as those with a viral load ≥20 k copies per milliliter. Permutation tests were conducted to account for dependency.

RESULTS

After controlling for total connections, age, substance use during sex, syphilis diagnosis (previous 12 months), and frequency of condomless anal sex (previous 6 months), we found a positive association between NVL and HIV infection. Compared with a network with all HIV-seronegative members, the odds of HIV infection with an NVL of <10% viremia were 1.85 (95% confidence interval: 1.18 to 2.92) times higher and those with an NVL of ≥10% viremia were 2.73 (95% confidence interval: 1.54 to 4.85) times higher.

CONCLUSIONS

We found a positive association between NVL and HIV seroprevalence. Although limited in its ability to infer causality, NVL could have substantial public health implications for persons most at risk for HIV infection, given that this novel metric avoids overreliance on individual level behavior or broad community indices.

Options for reducing HIV transmission related to the dead space in needles and syringes

BACKGROUND

When shared by people who inject drugs, needles and syringes with different dead space may affect the probability of HIV and hepatitis C virus (HCV) transmission differently.

METHODS

We measured dead space in 56 needle and syringe combinations obtained from needle and syringe programs across 17 countries in Europe and Asia. We also calculated the amounts of blood and HIV that would remain in different combinations following injection and rinsing.

RESULTS

Syringe barrel capacities ranged from 0.5 to 20 mL. Needles ranged in length from 8 to 38 mm. The average dead space was 3 μL in low dead space syringes with permanently attached needles, 13 μL in high dead space syringes with low dead space needles, 45 μL in low dead space syringes with high dead space needles, and 99 μL in high dead space syringes with high dead space needles. Among low dead space designs, calculated volumes of blood and HIV viral burden were lowest for low dead space syringes with permanently attached needles and highest for low dead space syringes with high dead space needles.

CONCLUSION

The dead space in different low dead space needle and syringe combinations varied substantially. To reduce HIV transmission related to syringe sharing, needle and syringe programs need to combine this knowledge with the needs of their clients.

Drug Use and Sexual HIV Transmission Risk Among Men Who have Sex with Men and Women (MSMW), Men Who have Sex with Men only (MSMO), and Men Who have Sex with Women Only (MSWO) and the Female Partners of MSMW and MSWO: A Network Perspective

We described drug use, sex risk, and STI/HIV among men who have sex with men and women (MSMW) and their female partners. We used the Network, Norms and HIV/STI Risk among Youth (NNAHRAY) study to evaluate drug use, sex risk, and biologically-confirmed STI/HIV in (1) MSMW and men who had sex with men only (MSMO) versus men who had sex with women only (MSWO) and (2) female partners of MSMW versus female partners of MSWO (N = 182 men, 152 women). MSMW versus MSWO had 30 to 60% increased odds of substance use, over twice the odds of multiple partnerships, and almost five times the odds of sex trade and HIV infection. Female partners of MSMW versus female partners of MSWO had approximately twice the odds of substance use and 1.5-2 times the odds of multiple partnerships and sex trade. Interventions should address STI/HIV risk among MSMW and their female partners.

The risk of HIV transmission at each step of the HIV care continuum among people who inject drugs: a modeling study

Background

People who inject drugs (PWID) are at continued risk for HIV in the U.S., and experience disparities across the HIV care continuum compared to other high-risk groups. Estimates of the risk of HIV transmission at each stage of the care continuum may assist in identifying public health priorities for averting incident infections among PWID, in addition to transmissions to sexual partners of PWID.

Methods

We created an agent-based model simulating HIV transmission and the HIV care continuum for PWID in New York City (NYC) in 2012. To account for sexual transmission arising from PWID to non-PWID, the simulation included the entire adult NYC population. Using surveillance data and estimates from the National HIV Behavioral Surveillance system, we simulated a dynamic sexual and injecting network. We estimated the proportion of HIV transmission events attributable to PWID in the following categories, those: without an HIV diagnosis (‘Undiagnosed’); diagnosed but not on antiretroviral therapy (ART) (‘Diagnosed − not on ART’); those who initiated ART but were not virally suppressed (‘Unsuppressed’); and, those who achieved viral suppression (‘Suppressed’).

Results

We estimated HIV incidence among PWID to be 113 per 100,000 person-years in 2012, with an overall incidence rate for the entire adult NYC population of 33 per 100,000 person-years. Despite accounting for only 33% of the HIV-infected PWID population, the Undiagnosed were associated with 52.6% (95% simulation interval [95% SI]: 47.1–57.0%) of total transmission events. The Diagnosed − not on ART population contributed the second-largest proportion of HIV transmissions, with 36.6% (95% SI: 32.2–41.5%). The Unsuppressed population contributed 8.7% (95% SI: 5.6–11.8%), and Suppressed 2.1% (95% SI: 1.1–3.9%), relatively little of overall transmission.

Conclusions

Among PWID in NYC, more than half (53%) of transmissions were from those who were unaware of their infection status and more than 36% were due to PWID who knew their status, but were not on treatment. Our results indicate the importance of early diagnosis and interventions to engage diagnosed PWID on treatment to further suppress population-level HIV transmission. Future HIV prevention research should focus on the elimination of identified and potential barriers to the testing, diagnosis, and retention of PWID on HIV treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4528-9) contains supplementary material, which is available to authorized users.

Cross-sectional association between ZIP code-level gentrification and homelessness among a large community-based sample of people who inject drugs in 19 US cities

BACKGROUND

Housing instability has been associated with poor health outcomes among people who inject drugs (PWID). This study investigates the associations of local-level housing and economic conditions with homelessness among a large sample of PWID, which is an underexplored topic to date.

METHODS

PWID in this cross-sectional study were recruited from 19 large cities in the USA as part of National HIV Behavioral Surveillance. PWID provided self-reported information on demographics, behaviours and life events. Homelessness was defined as residing on the street, in a shelter, in a single room occupancy hotel, or in a car or temporarily residing with friends or relatives any time in the past year. Data on county-level rental housing unaffordability and demand for assisted housing units, and ZIP code-level gentrification (eg, index of percent increases in non-Hispanic white residents, household income, gross rent from 1990 to 2009) and economic deprivation were collected from the US Census Bureau and Department of Housing and Urban Development. Multilevel models evaluated the associations of local economic and housing characteristics with homelessness.

RESULTS

Sixty percent (5394/8992) of the participants reported homelessness in the past year. The multivariable model demonstrated that PWID living in ZIP codes with higher levels of gentrification had higher odds of homelessness in the past year (gentrification: adjusted OR=1.11, 95% CI=1.04 to 1.17).

CONCLUSIONS

Additional research is needed to determine the mechanisms through which gentrification increases homelessness among PWID to develop appropriate community-level interventions.

Monitoring quality and coverage of harm reduction services for people who use drugs: a consensus study

BACKGROUND AND AIMS

Despite advances in our knowledge of effective services for people who use drugs over the last decades globally, coverage remains poor in most countries, while quality is often unknown. This paper aims to discuss the historical development of successful epidemiological indicators and to present a framework for extending them with additional indicators of coverage and quality of harm reduction services, for monitoring and evaluation at international, national or subnational levels. The ultimate aim is to improve these services in order to reduce health and social problems among people who use drugs, such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infection, crime and legal problems, overdose (death) and other morbidity and mortality.

METHODS AND RESULTS

The framework was developed collaboratively using consensus methods involving nominal group meetings, review of existing quality standards, repeated email commenting rounds and qualitative analysis of opinions/experiences from a broad range of professionals/experts, including members of civil society and organisations representing people who use drugs. Twelve priority candidate indicators are proposed for opioid agonist therapy (OAT), needle and syringe programmes (NSP) and generic cross-cutting aspects of harm reduction (and potentially other drug) services. Under the specific OAT indicators, priority indicators included 'coverage', 'waiting list time', 'dosage' and 'availability in prisons'. For the specific NSP indicators, the priority indicators included 'coverage', 'number of needles/syringes distributed/collected', 'provision of other drug use paraphernalia' and 'availability in prisons'. Among the generic or cross-cutting indicators the priority indicators were 'infectious diseases counselling and care', 'take away naloxone', 'information on safe use/sex' and 'condoms'. We discuss conditions for the successful development of the suggested indicators and constraints (e.g. funding, ideology). We propose conducting a pilot study to test the feasibility and applicability of the proposed indicators before their scaling up and routine implementation, to evaluate their effectiveness in comparing service coverage and quality across countries.

CONCLUSIONS

The establishment of an improved set of validated and internationally agreed upon best practice indicators for monitoring harm reduction service will provide a structural basis for public health and epidemiological studies and support evidence and human rights-based health policies, services and interventions.

The Interaction of Risk Network Structures and Virus Natural History in the Non-spreading of HIV Among People Who Inject Drugs in the Early Stages of the Epidemic

This article explores how social network dynamics may have reduced the spread of HIV-1 infection among people who inject drugs during the early years of the epidemic. Stochastic, discrete event, agent-based simulations are used to test whether a "firewall effect" can arise out of self-organizing processes at the actor level, and whether such an effect can account for stable HIV prevalence rates below population saturation. Repeated simulation experiments show that, in the presence of recurring, acute, and highly infectious outbreaks, micro-network structures combine with the HIV virus's natural history to reduce the spread of the disease. These results indicate that network factors likely played a significant role in the prevention of HIV infection within injection risk networks during periods of peak prevalence. They also suggest that social forces that disturb network connections may diminish the natural firewall effect and result in higher rates of HIV.

Sexual Risk and Transmission Behaviors, Partnerships and Settings Among Young Adult Nonmedical Opioid Users in New York City

Nonmedical prescription opioid use has become widespread. It can lead to heroin use, drug injection and HIV infection. We describe young adult opioid users' sexual risk behavior, partnerships and settings. 464 youth aged 18-29 who reported opioid use in the past 30 days were recruited using Respondent-Driven Sampling. Eligible participants completed a computer-assisted, interviewer-administered risk questionnaire and were tested for STIs and HIV. Participants (33% female; 66% white non-Hispanic) almost all had sex in the prior 90 days; 42% reported more than one partner. Same-sex sex was reported by 3% of men and 10% of women. Consistent condom use was rare. Seven percent reported group sex participation in the last 90 days but lifetime group sex was common among men and women. Young opioid users' unprotected sex, multiple partners and group sex puts them and others at high HIV and STI risk.

The global spread of HIV-1 subtype B epidemic

Human immunodeficiency virus type 1 (HIV-1) was discovered in the early 1980s when the virus had already established a pandemic. For at least three decades the epidemic in the Western World has been dominated by subtype B infections, as part of a sub-epidemic that traveled from Africa through Haiti to United States. However, the pattern of the subsequent spread still remains poorly understood. Here we analyze a large dataset of globally representative HIV-1 subtype B strains to map their spread around the world over the last 50years and describe significant spread patterns. We show that subtype B travelled from North America to Western Europe in different occasions, while Central/Eastern Europe remained isolated for the most part of the early epidemic. Looking with more detail in European countries we see that the United Kingdom, France and Switzerland exchanged viral isolates with non-European countries than with European ones. The observed pattern is likely to mirror geopolitical landmarks in the post-World War II era, namely the rise and the fall of the Iron Curtain and the European colonialism. In conclusion, HIV-1 spread through specific migration routes which are consistent with geopolitical factors that affected human activities during the last 50years, such as migration, tourism and trade. Our findings support the argument that epidemic control policies should be global and incorporate political and socioeconomic factors.

Reducing HIV infection in people who inject drugs is impossible without targeting recently-infected subjects

OBJECTIVE

Although our understanding of viral transmission among people who inject drugs (PWID) has improved, we still know little about when and how many times each injector transmits HIV throughout the duration of infection. We describe HIV dynamics in PWID to evaluate which preventive strategies can be efficient.

DESIGN

Due to the notably scarce interventions, HIV-1 spread explosively in Russia and Ukraine in 1990s. By studying this epidemic between 1995 and 2005, we characterized naturally occurring transmission dynamics of HIV among PWID.

METHOD

We combined publicly available HIV pol and env sequences with prevalence estimates from Russia and Ukraine under an evolutionary epidemiology framework to characterize HIV transmissibility between PWID. We then constructed compartmental models to simulate HIV spread among PWID.

RESULTS

In the absence of interventions, each injector transmits on average to 10 others. Half of the transmissions take place within 1 month after primary infection, suggesting that the epidemic will expand even after blocking all the post-first month transmissions. Primary prevention can realistically target the first month of infection, and we show that it is very efficient to control the spread of HIV-1 in PWID. Treating acutely infected on top of primary prevention is notably effective.

CONCLUSION

As a large proportion of transmissions among PWID occur within 1 month after infection, reducing and delaying transmissions through scale-up of harm reduction programmes should always form the backbone of HIV control strategies in PWID. Growing PWID populations in the developing world, where primary prevention is scarce, constitutes a public health time bomb.

Marijuana Use Among Young Black Men Who Have Sex With Men and the HIV Care Continuum: Findings From the uConnect Cohort

BACKGROUND

Young Black men who have sex with men (YBMSM) are at highest risk for HIV seroconversion in the United States. Successful movement through the HIV care continuum is an important intervention for limiting onwards HIV transmission.

OBJECTIVE

Little data exists on how substances most commonly used by YBMSM, such as marijuana, are related to the HIV continuum, which represents the primary aim of this study.

METHODS

A cohort of YBMSM (n = 618) was generated through respondent-driven sampling. Frequency of marijuana use and marijuana use as a sex-drug were assessed across the HIV care continuum using weighted logistic regression models.

RESULTS

Study participants reported more intermittent marijuana use (n = 254, 56.2%) compared to heavy use (n = 198, 43.8%). Our sample contained 212 (34.3%) HIV seropositive participants of which 52 (24.5%) were unaware of their HIV positive status. Study participants who were heavy marijuana users were more likely to be unaware of their HIV seropositive status (AOR: 4.18; 95% CI 1.26, 13.89). All other stages in the care continuum demonstrated no significant differences between those who use marijuana intermittently or heavily or as a sex-drug and nonusers.

CONCLUSIONS

YBMSM who used marijuana heavily were more likely to be HIV-positive unaware than those who never used marijuana. Findings were inconclusive regarding the relationships between marijuana use and other HIV care continuum metrics. However, knowledge of ones' HIV status is a critical requirement for engaging in care and may have implications for onwards HIV transmission.

Associations of place characteristics with HIV and HCV risk behaviors among racial/ethnic groups of people who inject drugs in the United States

PURPOSE

Investigate whether characteristics of geographic areas are associated with condomless sex and injection-related risk behavior among racial/ethnic groups of people who inject drugs (PWID) in the United States.

METHODS

PWID were recruited from 19 metropolitan statistical areas for 2009 National HIV Behavioral Surveillance. Administrative data described ZIP codes, counties, and metropolitan statistical areas where PWID lived. Multilevel models, stratified by racial/ethnic groups, were used to assess relationships of place-based characteristics to condomless sex and injection-related risk behavior (sharing injection equipment).

RESULTS

Among black PWID, living in the South (vs. Northeast) was associated with injection-related risk behavior (adjusted odds ratio [AOR] = 2.24, 95% confidence interval [CI] = 1.21-4.17; P = .011), and living in counties with higher percentages of unaffordable rental housing was associated with condomless sex (AOR = 1.02, 95% CI = 1.00-1.04; P = .046). Among white PWID, living in ZIP codes with greater access to drug treatment was negatively associated with condomless sex (AOR = 0.93, 95% CI = 0.88-1.00; P = .038).

CONCLUSIONS

Policies that increase access to affordable housing and drug treatment may make environments more conducive to safe sexual behaviors among black and white PWID. Future research designed to longitudinally explore the association between residence in the south and injection-related risk behavior might identify specific place-based features that sustain patterns of injection-related risk behavior.

Towards an HIV Role Theory: Drug-related Peer Beliefs and Role Strain Indicators as Predictors of Injection Risk Behaviors among Puerto Rican Injection Drug Users in New York and Puerto Rico

This study assesses whether injection risk behaviors (e.g., syringe sharing and sharing injection paraphernalia) can be understood using a model that highlights drug related peer beliefs and role strain/deprivation. Data were collected on 561 Puerto Rican injection drug users in New York and 313 in Puerto Rico. A drug peer beliefs scale and three indicators of role strain were used with other control variables in a hierarchical multiple logistic regression model. Both aspects of the model were significant predictors of HIV risk behaviors in New York, but only role strain was a significant predictor for injection drug users (IDUs) in Puerto Rico. Individual-based paradigms should incorporate peer beliefs and role strain/deprivation in order to reduce HIV risk behaviors.