Field Testing the "Avoid the Needle" Intervention for Persons at Risk for Transitioning to Injecting Drug Use in Tallinn, Estonia and New York City, USA.

This study aimed to field tested the "Avoid the Needle" (AtN) intervention to reduce transitions from non-injecting to injecting drug use in two different epidemiological settings. Respondent driven sampling was used to recruit current non-injecting drug users (NIDUs) in Tallinn, Estonia in 2018-19 and in New York City (NYC) in 2019-20. Both persons who had never injected and persons who had previously injected but not in the last 6 months were eligible; a structured interview was administered, a blood sample collected, and the intervention administered by trained interventionists. We recruited 19 non-injectors from Tallinn and 140 from NYC. Participants in Tallinn were younger and had begun using drugs at earlier ages than participants in NYC. The primary drugs used in Tallinn were amphetamine, fentanyl, and opioid analgesics, while in NYC they were heroin, cocaine, speedball, and fentanyl. Six-month follow-up data were obtained from 95% of participants in Tallinn. The study was interrupted by COVID-19 lockdown in NYC, but follow-up data were obtained from 59% of participants. There were minimal transitions to injecting: 1/18 in Tallinn and 0/83 in NYC. There were significant declines in the frequencies of using readily injectable drugs (fentanyl, amphetamine, heroin, cocaine) from baseline to follow-up in both sites (Cochran-Armitage tests for trend, χ2 = 21.3, p < 0.001 for New York City; and χ2 = 3.9, p = 0.048 for Tallinn). Reducing transitions into injecting is a potentially very important method for reducing HIV transmission and other harms of drug use. Further investigation and implementation of AtN type interventions is warranted.

Program Adaptations to Provide Harm Reduction Services During the COVID-19 Pandemic: A Qualitative Study of Syringe Services Programs in the U.S.

Syringe services programs (SSPs) are essential to preventing injection drug use-related infections and overdose death among people who use drugs (PWUD). The novel coronavirus (COVID-19) pandemic initially impeded SSPs' operations. To effectively support these programs, information is needed regarding SSPs' experiences adapting their services and the challenges posed by COVID-19. We conducted qualitative interviews with leadership and staff from a sample of 31 U.S. SSPs. Respondents discussed urgent concerns including reduced reach of services, suspended HIV/hepatitis C testing, high COVID-19 risk among PWUD, and negative impacts of isolation on overdose and mental health. They also noted opportunities to improve future services for PWUD, including shifting to evidence-based distribution practices and maintaining regulatory changes that increased access to opioid use disorder medications post-pandemic. Findings can inform efforts to support SSPs in restoring and expanding services, and provide insight into SSPs' role in engaging PWUD during the COVID-19 response and future emergencies.

RESUMEN: Los programas de servicios de jeringas (reconocido como SSP en inglés) son esenciales para prevenir las infecciones relacionadas con el consumo de drogas inyectables y la muerte por sobredosis entre las personas que consumen drogas (reconocidos como PWUD en ingles). La nueva pandemia del coronavirus (COVID-19) inicialmente impidió las operaciones de los SSP. Para apoyar eficazmente estos programas, se necesita información sobre las experiencias de los SSP que adaptan sus servicios y los desafíos que plantea COVID-19. Realizamos entrevistas cualitativas con el liderazgo y el personal de una muestra de 31 SSPs de EE.UU. Los encuestados discutieron las preocupaciones urgentes, incluyendo la reducción del alcance de los servicios, la suspensión de las pruebas de VIH/hepatitis C, el alto riesgo de COVID-19 entre la PWUD, y los impactos negativos del aislamiento en las sobredosis y la salud mental. También identificaron las oportunidades de mejorar los servicios futuros para las PWUD, incluyendo el cambio a prácticas de distribución basadas en evidencias y el mantenimiento de cambios regulatorios que aumentaran el acceso a medicamentos para el trastorno por consumo de opiáceos después de la pandemia. La información que se encontró en este estudio se puede utilizar junto los esfuerzos para apoyar a los SSP en la restauración y expansión de los servicios, y proporcionar información sobre el papel de los SSP en la participación de PWUD durante la respuesta covid-19 futuras emergencias.

Place-Based Predictors of HIV Viral Suppression and Durable Suppression Among Men Who Have Sex With Men in New York City.

We explore relationships between place characteristics and HIV viral suppression among HIV-positive men who have sex with men (MSM) in New York City (NYC). We conducted multilevel analyses to examine associations of United Hospital Fund (UHF)-level characteristics to individual-level suppression and durable suppression among MSM. Individual-level independent and dependent variables came from MSM in NYC's HIV surveillance registry who had been diagnosed in 2009-2013 (N = 7159). UHF-level covariates captured demographic composition, economic disadvantage, healthcare access, social disorder, and police stop and frisk rates. 56.89% of MSM achieved suppression; 35.49% achieved durable suppression. MSM in UHFs where 5-29% of residents were Black had a greater likelihood of suppression (reference: ≥30% Black; adjusted relative risk (ARR) = 1.07, p = 0.04). MSM in UHFs with <30 MSM-headed households/10,000 households had a lower likelihood of achieving durable suppression (reference: ≥60 MSM-headed households/10,000; ARR = 0.82; p = 0.05). Place characteristics may influence viral suppression. Longitudinal research should confirm these associations.

Providing ART to HIV Seropositive Persons Who Use Drugs: Progress in New York City, Prospects for "Ending the Epidemic".

New York City has experienced the largest HIV epidemic among persons who use psychoactive drugs. We examined progress in placing HIV seropositive persons who inject drugs (PWID) and HIV seropositive non-injecting drug users (NIDU) onto antiretroviral treatment (ART) in New York City over the last 15 years. We recruited 3511 PWID and 3543 NIDU from persons voluntarily entering drug detoxification and methadone maintenance treatment programs in New York City from 2001 to 2014. HIV prevalence declined significantly among both PWID and NIDU. The percentage who reported receiving ART increased significantly, from approximately 50 % (2001-2005) to approximately 75 % (2012-2014). There were no racial/ethnic disparities in the percentages of HIV seropositive persons who were on ART. Continued improvement in ART uptake and TasP and maintenance of other prevention and care services should lead to an "End of the AIDS Epidemic" for persons who use heroin and cocaine in New York City.

Barriers to engaging people who use drugs in harm reduction services during the COVID-19 pandemic: A mixed methods study of syringe services program perspectives.

BACKGROUND: Syringe services programs (SSPs) provide critical evidence-based public health services that decrease harms from drug use for people who use drugs (PWUD). Many SSPs have experienced significant and evolving COVID-19-related disruptions. We aimed to characterize the impacts of COVID-19 on SSP operations in the United States approximately one year into the pandemic. METHODS: Participating sites, selected from a national sample of SSPs, completed a semi-structured interview via teleconference and brief survey evaluating the impacts of COVID-19 on program operations. Data collection explored aspects of program financing, service delivery approaches, linkages to care, and perspectives on engaging PWUD in services one year into the pandemic. Interview data were analyzed qualitatively using Rapid Assessment Process. Survey data were analyzed using descriptive statistics and triangulated with qualitative findings. RESULTS: 27 SSPs completed study-related interviews and surveys between February 2021 - April 2021. One year into the pandemic, SSPs reported continuing to adapt approaches to syringe distribution in response to COVID-19, and identified multiple barriers that hindered their ability to engage program participants in services, including 1) isolation and decreased connectivity with participants, 2) resource restrictions that limit responsiveness to participant needs, 3) reduced capacity to provide on-site HIV/HCV testing and treatment linkages, and 4) changing OUD treatment modalities that were a "double-edged sword" for PWUD. Quantitative survey responses aligned with qualitative findings, highlighting increases in the number of syringes distributed, increases in mobile and home delivery services, and reductions in on-site HIV and HCV testing. CONCLUSION: These data illuminate persistent and cascading risks of isolation, reduced access to services, and limited engagement with program participants that resulted from COVID-19 and continue to create barriers to the delivery of critical harm reduction services. Findings emphasize the need to ensure SSPs have the resources and capacity to adapt to changing public health needs, particularly as the COVID-19 pandemic continues to evolve.

A stakeholder-driven framework for measuring potential change in the health risks of people who inject drugs (PWID) during the COVID-19 pandemic.

BACKGROUND: People who inject drugs (PWID) have likely borne disproportionate health consequences of the COVID-19 pandemic. PWID experienced both interruptions and changes to drug supply and delivery modes of harm reduction, treatment, and other medical services, leading to potentially increased risks for HIV, hepatitis C virus (HCV), and overdose. Given surveillance and research disruptions, proximal, indirect indicators of infectious diseases and overdose should be developed for timely measurement of health effects of the pandemic on PWID. METHODS: We used group concept mapping and a systems thinking approach to produce an expert stakeholder-generated, multi-level framework for monitoring changes in PWID health outcomes potentially attributable to COVID-19 in the U.S. This socio-ecological measurement framework elucidates proximal and distal contributors to infectious disease and overdose outcomes, many of which can be measured using existing data sources. RESULTS: The framework includes multi-level components including policy considerations, drug supply/distribution systems, the service delivery landscape, network factors, and individual characteristics such as mental and general health status and service utilization. These components are generally mediated by substance use and sexual behavioral factors to cause changes in incidence of HIV, HCV, sexually transmitted infections, wound/skin infections, and overdose. CONCLUSION: This measurement framework is intended to increase the quality and timeliness of research on the impacts of COVID-19 in the context of the current pandemic and future crises. Next steps include a ranking process to narrow the drivers of change in health risks to a concise set of indicators that adequately represent framework components, can be written as measurable indicators, and are quantifiable using existing data sources, as well as a publicly available web-based platform for summary data contributions.

An application of agent-based modeling to explore the impact of decreasing incarceration rates and increasing drug treatment access on sero-discordant partnerships among people who inject drugs.

BACKGROUND: People who inject drugs (PWID) lag behind other key populations in HIV care continuum outcomes. The impacts of criminal justice reform and increasing drug treatment access on HIV have been underexplored. METHODS: We developed agent-based models (ABM) of sexual partnerships among PWID and non-PWID, and injection equipment-sharing partnerships among PWID in five US cities (Baltimore, Boston, Miami, New York City, San Francisco) over 3 years. The first set of ABM projected changes in partnership discordance among PWID as a function of decreasing ZIP code-level incarceration rates. The second set projected discordance as a function of increasing ZIP code-level drug treatment access. ABM were parameterized and validated overall, and by city and PWID race/ethnicity (Black, Latino, White) using National HIV Behavioral Surveillance data, administrative ZIP code-level data, surveillance reports and prior literature. Informed by research on prisoner release and community-level HIV prevalence, reductions in incarceration rates were fixed at 5% and 30% and respectively projected to increase ZIP code-level HIV prevalence by 2% and 12%. Increases in drug treatment access were fixed at 30% and 58%. RESULTS: In each city, a 30% reduction in ZIP code-level incarceration rates and 12% increase in ZIP code-level HIV prevalence significantly increased sero-discordance among at least one racial/ethnic group of PWID by 1-3 percentage points. A 5% reduction in incarceration rates, and 30% and 58% increases in drug treatment access, led to isolated significant changes in sero-discordance among Black and White PWID that were less than 1 percentage point. CONCLUSION: Reductions in incarceration rates may lead to short-term increases in sero-discordant partnerships among some PWID by increasing community-level HIV prevalence. Efforts to increase HIV testing, engagement in care and community reintegration post release, should be strengthened in the wake of incarceration reform. Additional research should confirm these findings and explore the lack of widespread impacts of drug treatment in this study.

Buprenorphine in maintenance treatment: experience among Italian physicians in drug addiction centers.

The aim of this study was to assess the attitudes of Italian physicians regarding buprenorphine and its clinical use approximately 6 years after the medication was introduced into clinical practice. The sample consisted of 305 randomly selected physicians, working in public centers of drug addiction. In Italy buprenorphine seems a valid tool in the field of drug addiction treatment, although it is far from replacing methadone even though it seems to guarantee better compliance. Interviewees follow clinical experience more than international guidelines, with pharmaceutical company representatives as the most cited source for information about the medication. The data also suggests a need for the development of formal guidelines for treatment with buprenorphine in Italy.

Psychiatric Comorbidities among People Who Inject Drugs in Hai Phong, Vietnam: The Need for Screening and Innovative Interventions.

The objective of this study is to describe psychiatric comorbidities, associated factors, and access to psychiatric assessment and care in a cohort of people who inject drugs (PWID) in Hai Phong, Vietnam. Mental health was assessed after 12 months' follow-up using the Mini International Neuropsychiatric Interview questionnaire (MINI 5.0.0). PWID medical history, drug use, and sociodemographic and clinical characteristics were also collected. Among 188 PWID who participated in the assessment, 48 (25.5%) had at least one psychiatric disorder and 19 (10.1%) had 2 or more psychiatric disorders. The most common current psychiatric disorders were major depressive episode (12.2%) and psychotic disorder (4.8%), reaching 10.1% for the latter when lifetime prevalence was considered. Females were more likely than males to have at least one psychiatric disorder, a major depressive disorder, or an anxiety disorder. Methamphetamine use was associated with an increased risk of presenting a lifetime psychotic syndrome. Problematic alcohol consumption was associated with an increased risk of having at least one psychiatric disorder. Psychiatric comorbidities are frequent among PWID in Vietnam. These results highlight the need for routine assessment and innovative interventions to address mental health needs among PWID. Community-based interventions targeting mental health prevention and care should be strongly supported.

Patterns of HIV prevalence and HIV risk behaviors among injection drug users prior to and 24 months following implementation of cross-border HIV prevention interventions in northern Vietnam and southern China.

In 2002, we implemented a 4-year HIV prevention intervention for injection drug users (IDUs) in Lang Son Province, Vietnam, and Ning Ming County, Guangxi Province, China, a cross-border region seriously affected by inter-twined epidemics of heroin injection and HIV infection. The interventions involve peer education on HIV risk reduction and provision of new needles/syringes through direct distribution and pharmacy vouchers. We consider this to be a structural intervention in which risk reduction information and sterile injection equipment are diffused through the IDU populations and not limited to those who actually interact with peer educators. The evaluation of structural interventions poses complex methodological challenges. The evaluation of our interventions relies primarily on cross-sectional surveys (interviews and HIV testing) of samples of IDUs selected using a combination of targeted cluster and snowball methods. We consider this to be an appropriate, albeit imperfect, design given the study context. This paper presents analyses of data from the IDU surveys conducted just prior to implementation of the interventions and 24 months thereafter. The cross-border interventions have reached large proportions of the IDUs in the project sites, drug-related HIV risk behaviors have declined in frequency, and HIV prevalence among IDUs has been stable in China and declined in Vietnam over the 24 months since the interventions were implemented. Attribution of these positive trends to the interventions must be qualified in light of possible sampling biases and the absence of control groups. However, we believe that the structural interventions implemented by the cross-border project have played a role in stabilizing HIV prevalence among IDUs two years after they were initiated. Evidence of further diffusion of the interventions among IDUs and continued stability or decline of HIV prevalence would strengthen this case.

From Long-Term Injecting to Long-Term Non-Injecting Heroin and Cocaine Use: The Persistence of Changed Drug Habits.

OBJECTIVES: Transitioning from injecting to non-injecting routes of drug administration can provide important individual and community health benefits. We assessed characteristics of persons who had ceased injecting while continuing to use heroin and/or cocaine in New York City. METHODS: We recruited subjects entering Mount Sinai Beth Israel detoxification and methadone maintenance programs between 2011 and 2015. Demographic information, drug use histories, sexual behaviors, and "reverse transitions" from injecting to non-injecting drug use were assessed in structured face-to-face interviews. There were 303 "former injectors," operationally defined as persons who had injected at some time in their lives, but had not injected in at least the previous 6 months. Serum samples were collected for HIV and HCV testing. RESULTS: Former injectors were 81% male, 19% female, 17% White, 43% African-American, and 38% Latino/a, with a mean age of 50 (SD=9.2), and were currently using heroin and/or cocaine. They had injected drugs for a mean of 14 (SD=12.2) years before ceasing injection, and a mean of 13 (SD=12) years had elapsed since their last injection. HIV prevalence among the sample was 13% and HCV prevalence was 66%. The former injectors reported a wide variety of reasons for ceasing injecting. Half of the group appeared to have reached a point where relapse back to injecting was no longer problematic: they had not injected for three or more years, were not deliberately using specific techniques to avoid relapse to injecting, and were not worried about relapsing to injecting. CONCLUSIONS: Former injectors report very-long term behavior change toward reduced individual and societal harm while continuing to use heroin and cocaine. The behavior change appears to be self-sustaining, with full replacement of an injecting route of drug administration by a non-injecting route of administration. Additional research on the process of long-term cessation of injecting should be conducted within a "combined prevention and care" approach to HIV and HCV infection among persons who use drugs.

What's community got to do with it? Implementation models of syringe exchange programs.

Syringe exchange programs (SEPs) have been shown to be highly effective in reducing HIV transmission among injection drug users (IDUs). Despite this evidence, SEPs have not been implemented in many communities experiencing HIV epidemics among IDUs. We interviewed 17 key informants in nine U.S. cities to identify factors and conditions that facilitated or deterred the adoption of SEPs. Cities were selected to represent diversity in size, geographic location, AIDS incidence rates, and SEP implementation. Key informants included HIV prevention providers, political leaders, community activists, substance use and AIDS researchers, and health department directors. SEPs were established by one or more of three types of implementation models: (a) broad community coalition support, (b) community activist initiative, and (c) top-down decision making by government authorities. In each model, coalition building and community consultation were critical steps for the acceptance and sustainability of SEPs. When others were not prepared to act, community activists spearheaded SEP development, taking risks in the face of opposition, but often lacked the resources to sustain their efforts. Leadership from politicians and public health officials provided needed authority, clout, and access to resources. Researchers and scientific findings lent force and legitimacy to the effort. Rather than adopting adversarial positions, successful SEP implementers worked with or avoided the opposition. Fear of repercussions and lack of leadership were the greatest barriers to implementing SEPs. Communities that successfully implemented SEPs were those with activists willing to push the agenda, public officials willing to exercise leadership, researchers able to present authoritative findings, and proponents who effectively mobilized resources and worked to build community coalitions, using persistent but nonadversarial advocacy.

Compliance with hepatitis B vaccination in 1175 heroin users and risk factors associated with lack of vaccine response.

AIMS: To investigate the feasibility of hepatitis B vaccination among heroin users, assessing adherence to the vaccination schedules and identifying factors associated with antibody response. DESIGN AND PARTICIPANTS: A large cohort study in nine public centres for drug users (PCDUs) in north-eastern Italy, with data collected between January 1989 and December 1998. A total of 1175 heroin users were selected and vaccinated with a recombinant vaccine using two schedules (0-1-6 months and 0-1-2 months). FINDINGS: Eighty-eight per cent of patients completed the vaccination series and a protective antibody response occurred in 77% of subjects. Completion of the vaccination series was not related to the length of the vaccination schedule or whether the patient was still in drug abuse treatment at the end of the series, but was related strongly to the number of patients enrolled at each PCDU (Spearman correlation = - 0.93, P < 0.001). Four variables were significantly associated with lack of seroconversion in response to vaccination: older age (AOR = 0.91 per year, 95% CI 0.88-0.94, P < 0.001), 2-month vaccination schedule (AOR = 3.10, 95% CI 2.06-4.68, P < 0.001), HCV seropositivity (AOR = 0.69, 95% CI 0.47-0.99, P = 0.04), HIV seropositivity (AOR = 0.27, 95% CI 0.10-0.77, P = 0.01). CONCLUSIONS: A large-scale, multi-site hepatitis B vaccination programme for heroin users proved feasible and effective. The factors associated with a lack of antibody response may be useful in identifying patients who would benefit most from routine post-vaccination testing, with booster doses for non-responders. These results suggest that hepatitis B vaccination for drug users should become a routine public health practice.

Heterosexual relationships among heroin users in Italy.

This study investigated how many stable partners of drug users (DUs) had a history of drug use or were current DUs. Of 589 DUs interviewed, 41% reported that they had a partner with current or previous experience of drug addiction. A strong gender difference emerged: 77% of female DUs reported a stable relationship with partners with a history of addiction, versus only 30% for male DUs. Partners with a history of drug dependence are more likely to be: male, older, with a lower educational level and a lower rate of stable employment than partners without a history of drug addiction. Logistic regression analysis indicated that the characteristics of heroin users who have current partners with histories of drug use include: female gender, older age, living with a partner, lengthy duration of the relationship and HIV positive status. Fewer subjects are married if the partner has a history of addiction, and there is an association between lengthy drug use and partner without drug addiction history. The high percentage (59%) of subjects who were in stable relationships with partners without histories of heroin addiction and the relatively long duration of these relationships, raises the issue of possible transmission of blood-borne viruses from the DUs to their sexual partners. The study does suggest the need for consideration of sexual partnerships and gender differences in providing drug abuse treatment for heroin users.

Changes in quality of life (WHOQOL-BREF) and addiction severity index (ASI) among participants in opioid substitution treatment (OST) in low and middle income countries: an international systematic review.

BACKGROUND: Opioid substitution treatment (OST) can increase quality of life (WHOQOL-BREF) and reduce addiction severity index (ASI) scores among participants over time. OST program participants have noted that improvement in quality of life is one of the most important variables to their reduction in drug use. However, there is little systematic understanding of WHOQOL-BREF and ASI domain changes among OST participants in low and middle-income countries (LMIC). METHODS: Utilizing PRISMA guidelines we conducted a systematic literature search to identify OST program studies documenting changes in WHOQOL-BREF or ASI domains for participants in buprenorphine or methadone programs in LMIC. Standardized mean differences for baseline and follow-up domain scores were compared along with relationships between domain scores, OST dosage, and length of follow-up. RESULTS: There were 13 OST program studies with 1801 participants from five countries eligible for inclusion in the review. Overall, statistically significant changes were noted in all four WHOQOL-BREF domain and four of the seven ASI domain scores (drug, psychological, legal, and family) documented in studies. Dosage of pharmacologic medication and length of follow-up did not affect changes in domain scores. CONCLUSION: WHOQOL-BREF and ASI domain scoring is a useful tool in measuring overall quality of life and levels of addiction among OST participants. Coupled with measurements of blood-borne infection, drug use, relapse, and overdose, WHOQOL-BREF and ASI represent equally important tools for evaluating the effects of OST over time and should be further developed as integrated tools in the evaluation of participants in LMIC.

To use or not to use: an update on licit and illicit ketamine use.

Ketamine, a derivative of phencyclidine that was developed in the 1960s, is an anesthetic and analgesic with hallucinogenic effects. In this paper, the pharmacological and toxicological effects of ketamine are briefly reviewed. Ketamine possesses a wide safety margin but such a therapeutic benefit is somewhat offset by its emergence phenomenon (mind-body dissociation and delirium) and hallucinogenic effects. The increasing abuse of ketamine, initially predominantly in recreational scenes to experience a "k-hole" and other hallucinatory effects but more recently also as a drug abused during the workday or at home, has further pushed governments to confine its usage in many countries. Recently, urinary tract dysfunction has been associated with long-term ketamine use. In some long-term ketamine users, such damage can be irreversible and could result in renal failure and dialysis. Although ketamine has not yet been scheduled in the United Nations Conventions, previous studies using different assessment parameters to score the overall harms of drugs indicated that ketamine may cause more harm than some of the United Nations scheduled drugs. Some countries in Southeast and East Asia have reported an escalating situation of ketamine abuse. Dependence, lower urinary tract dysfunction, and sexual impulse or violence were the most notable among the ketamine-associated symptoms in these countries. These results implied that the danger of ketamine may have been underestimated previously. Therefore, the severity levels of the ketamine-associated problems should be scrutinized more carefully and objectively. To prevent ketamine from being improperly used and evolving into an epidemic, a thorough survey on the prevalence and characteristics of illicit ketamine use is imperative so that suitable policy and measures can be taken. On the other hand, recent findings that ketamine could be useful for treating major depressive disorder has given this old drug a new impetus. If ketamine is indeed a remedy for treating depression, more research on the risks and benefits of its clinical use will be indispensable.

Learning from HIV epidemics among injecting drug users.

HIV/AIDS was the defining issue for international harm reduction during its first twenty years. This issue was marked by strong contrasts: rapid HIV transmission in some populations of injecting drug users, and close to elimination of HIV in other populations; a formidable research base for designing effective HIV programmes and persistent political problems in implementing evidence-based programmes on a public health scale. Elevated rates of HIV infection among ethnic minority drug users have occurred in many different countries. We do not yet have systematic knowledge of how to reduce stigmatization of AIDS or people who use drugs. Nevertheless, international harm reduction for people who use drugs has moved beyond HIV/AIDS to a variety of other health and social problems, while retaining firm bases in science and human rights.

Mortality risk among recent-onset injection drug users in five U.S. cities.

To quantify the risk of death among recent-onset (< 5 years) injection drug users, we enrolled 2089 injection drug users (IDUs) age