Faculty Bibliography

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.

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.

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.

OBJECTIVE:Estimates for the contribution of transmission arising from acute HIV infections (AHIs) to overall HIV incidence vary significantly. Furthermore, little is known about AHI-attributable transmission among people who inject drugs (PWID), including the extent to which interventions targeting chronic infections (e.g. HAART as prevention) are limited by AHI transmission. Thus, we estimated the proportion of transmission events attributable to AHI within the mature HIV epidemic among PWID in New York City (NYC). DESIGN:Modeling study. METHODS:We constructed an interactive sexual and injecting transmission network using an agent-based model simulating the HIV epidemic in NYC between 1996 and 2012. Using stochastic microsimulations, we cataloged transmission from PWID based on the disease stage of index agents to determine the proportion of infections transmitted during AHI (in primary analyses, assumed to last 3 months). RESULTS:Our calibrated model approximated the epidemiological features of the mature HIV epidemic in NYC between 1996 and 2012. Annual HIV incidence among PWID dropped from approximately 1.8% in 1996 to 0.7% in 2012. Over the 16-year period, AHI accounted for 4.9% (10th/90th percentile: 0.1-12.3%) of incident HIV cases among PWID. The annualized contribution of AHI increased over this period from 3.6% in 1996 to 5.9% in 2012. CONCLUSION:Our results suggest that, in mature epidemics such as NYC, between 3% and 6% of transmission events are attributable to AHI among PWID. Current HIV treatment as prevention strategies are unlikely to be substantially affected by AHI-attributable transmission among PWID populations in mature epidemic settings.

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.

Macro-social/structural events ("big events") such as wars, disasters, and large-scale changes in policies can affect HIV transmission by making risk behaviors more or less likely or by changing risk contexts. The purpose of this study was to develop new measures to investigate hypothesized pathways between macro-social changes and HIV transmission. We developed novel scales and indexes focused on topics including norms about sex and drug injecting under different conditions, involvement with social groups, helping others, and experiencing denial of dignity. We collected data from 300 people who inject drugs in New York City during 2012-2013. Most investigational measures showed evidence of validity (Pearson correlations with criterion variables range = 0.12-0.71) and reliability (Cronbach's alpha range = 0.62-0.91). Research is needed in different contexts to evaluate whether these measures can be used to better understand HIV outbreaks and help improve social/structural HIV prevention intervention programs.

This paper reviews and then discusses selected findings from a seventeen year study about the population prevalence of people who inject drugs (PWID) and of HIV prevalence and mortality among PWID in 96 large US metropolitan areas. Unlike most research, this study was conducted with the metropolitan area as the level of analysis. It found that metropolitan area measures of income inequality and of structural racism predicted all of these outcomes, and that rates of arrest for heroin and/or cocaine predicted HIV prevalence and mortality but did not predict changes in PWID population prevalence. Income inequality and measures of structural racism were associated with hard drug arrests or other properties of policing. These findings, whose limitations and implications for further research are discussed, suggest that efforts to respond to HIV and to drug injection should include supra-individual efforts to reduce both income inequality and racism. At a time when major social movements in many countries are trying to reduce inequality, racism and oppression (including reforming drug laws), these macro-social issues in public health should be both addressable and a priority in both research and action.

We investigated how different models of HIV transmission, and assumptions regarding the distribution of unprotected sex and syringe-sharing events ('risk acts'), affect quantitative understanding of HIV transmission process in people who inject drugs (PWID). The individual-based model simulated HIV transmission in a dynamic sexual and injecting network representing New York City. We constructed four HIV transmission models: model 1, constant probabilities; model 2, random number of sexual and parenteral acts; model 3, viral load individual assigned; and model 4, two groups of partnerships (low and high risk). Overall, models with less heterogeneity were more sensitive to changes in numbers risk acts, producing HIV incidence up to four times higher than that empirically observed. Although all models overestimated HIV incidence, micro-simulations with greater heterogeneity in the HIV transmission modelling process produced more robust results and better reproduced empirical epidemic dynamics.