Cohort studies of young (aged 18-30 years) injecting drug users recruited in 1997-1999 in the Harlem and Lower East Side areas of New York City, New York, were used to assess the incidence of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV). The authors found that HIV incidence was low at both sites: 0.8/100 person-years at the Harlem site and 0/100 person-years at the Lower East Side site. In contrast, HBV incidence was moderate (12.2/100 person-years) at the Harlem site and high (30.7/100 person-years) at the Lower East Side site. Similarly, HCV incidence was moderate (9.3/100 person-years) at the Harlem site and high (34.0/100 person-years) at the Lower East Side site. Results show that high rates of HBV and HCV transmission do not imply high rates of HIV transmission, even within an area of high HIV seroprevalence.

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Illicit drug use in urban settings is a major public health problem. A range of individual level factors are known to influence drug use and its consequences, and a number of recent studies have suggested that the neighborhood in which an individual lives may also play a role. However, studies seeking to identify neighborhood-level determinants of drug use, particularly among marginalized urban populations, need to overcome significant challenges, particularly in the area of sampling and recruitment. One key issue is defining functional neighborhoods that are relevant to local residents. Another arises from the need to sample a representative or even a diverse population when studying marginalized groups such as illicit drug users. These are common problems that raise particular challenges when both need to be addressed in the same study. For example, many sampling approaches for neighborhood-level studies have included some form of random sample of households, but this may systematically overlook marginalized populations. On the other hand, the sampling approaches commonly used in studies of hidden populations such as chain referral, snow ball, and more recently, respondent-driven sampling, typically expand beyond a geographic "neighborhood." We describe the organization and rationale for the IMPACT Studies in New York City as a case illustration on how such issues may be addressed.

Health insurance was strongly associated with use of health care, particularly among those who attend NEPs. Young adult IDUs may benefit from increased efforts to help them arrange and maintain health insurance coverage, potentially at NEPs. NEPs may be connecting young IDUs with health insurance to medical care through referrals.

Surveillance data suggests that use of ecstasy in the U.S. is predominantly among white adolescent and young adults. To investigate ecstasy use among substance users in New York City we added questions to ongoing efforts to recruit heroin and cocaine users. Of 715 participants recruited, 58.3% were injection drug users (IDUs). The median age was 32 (range 17-64), 76.4% were male, 49.0% were currently homeless, 62.4% were Hispanic, 27.3% were black, and 34.5% were born outside the United States. Overall, 23.4% used ecstasy in their lifetime and 11.9% had used in the last-6 months. In multivariate logistic regression, correlates of lifetime ecstasy use included younger age, being born in the U.S., and current homelessness. We observed a significant interaction between injection drug use and race where, compared to black non-IDUs, Hispanic non-IDUs, and white IDUs were significantly more likely to have a history of lifetime ecstasy use while black IDUs were significantly less likely. These findings are limited to persons who use other drugs, but suggest that further investigation of ecstasy use in minority populations is warranted.