Alan Neaigus

Sociometric risk networks and risk for HIV infection.

OBJECTIVES This study examined whether networks of drug-injecting and sexual relationships among drug injectors are associated with individual human immunodeficiency virus (HIV) serostatus and with behavioral likelihood of future infection. METHODS A cross-sectional survey of 767 drug injectors in New York City was performed with chain-referral and linking procedures to measure large-scale (sociometric) risk networks. Graph-theoretic algebraic techniques were used to detect 92 connected components (drug injectors linked to each other directly or through others) and a 105-member 2-core within a large connected component of 230 members. RESULTS Drug injectors in the 2-core of the large component were more likely than others to be infected with HIV. Seronegative 2-core members engaged in a wide range of high-risk behaviors, including engaging in risk behaviors with infected drug injectors. CONCLUSIONS Sociometric risk networks seem to be pathways along which HIV travels in drug-injecting peer groups. The cores of large components can be centers of high-risk behaviors and can become pockets of HIV infection. Preventing HIV from reaching the cores of large components may be crucial in preventing widespread HIV epidemics.

High-risk personal networks and syringe sharing as risk factors for HIV infection among new drug injectors.

In a cross-sectional study of 174 new injecting drug users (IDUs) in New York City who had injected for < or = 6 years, we examined whether those who both share syringes and have personal risk networks that include high-risk injectors are particularly likely to be infected with HIV. Subjects were street recruited between July 1991 and January 1993, were interviewed about their risk behaviors in the prior 2 years and their personal risk networks with other IDUs in the prior 30 days, and were tested for HIV; 20% were HIV seropositive. Among those who both shared syringes and had a personal risk network member who injected more than once a day, 40% were HIV seropositive (versus 14% for others, p < 0.001). In simultaneous multiple logistic regression, the interaction of both sharing syringes and having a personal risk network member who injected more than once a day remained independently and significantly associated with being HIV seropositive (OR, 3.57; 95% CI, 1.22, 10.43; p < 0.020), along with Latino race/ethnicity and exchanging sex for money or drugs. These findings suggest that the combination of sharing syringes with having a high-risk personal network is a risk factor for HIV infection among new IDUs. Studies of risk factors for HIV infection among new IDUs and interventions to reduce the spread of HIV among them should focus on their risk networks as well as their risk behaviors.

Syringe-mediated drug-sharing (backloading) : a new risk factor for HIV among injecting drug users

Background:In syringe-mediated drug-sharing (backloading), injecting drug users (IDU) use their syringes to mix drugs and to give measured shares to other IDU by squirting drug solution into the syringes of other IDU. Backloading has been discussed as a potential HIV risk factor, but its role as an HIV transmission route has not been established empirically. Methods:Six hundred and sixty IDU who had injected drugs in the previous 2 years were street-recruited from Bushwick, New York City through chain referral, tested for HIV antibody and interviewed about sexual and drug-risk behaviors. Results:Receiving drugs via backloading in the previous 2 years was reported by 24.5% of the subjects. These subjects had significantly higher HIV seroprevalence than those who did not receive drugs by backloading (odds ratio, 2.2; 95% confidence interval, 1.5–3.1). Backloading remained positively and significantly associated with HIV seropositivity in stepwise logistic regression, and in a series of simultaneous logistic models controlling for sociodemographic variables and for sexual and drug risk variables. Conclusions:Backloading can be a route of HIV transmission among IDU and should be incorporated into risk-factor studies and HIV transmission modeling. Many IDU who avoid other high-risk drug-injection practices may overlook the risk of backloading. HIV prevention programs should warn IDU against syringe-mediated drug-sharing and work together to develop ways to avoid it. AIDS 1993, 7:1653–1660

Transitions to injecting drug use among noninjecting heroin users: social network influence and individual susceptibility.

Objectives: To determine the incidence/predictors of transitions to injecting among noninjecting heroin users (NIUs). Methods: Street-recruited NIUs in New York City, March/1996-March/2003, were interviewed for a prospective cohort study about social network influence (communication promoting injecting; exposure to injectors) and individual susceptibility. A transition to injecting was the first drug injection following baseline. Hazards ratios (HRs) (P < 0.05) were estimated by Cox proportional hazards regression, stratified by baseline injecting history. Results: Of 369 (64% of 579) followed, former-injectors were more likely to transition to injecting (33% or 53/160 vs. 12% or 25/209; 16.0/100 person-years-at-risk [pyar] vs. 4.6/100 pyar; HR = 3.25). Independent predictors among never-injectors included using ≥2 bags of heroin daily (HR = 7.0); social network influence (communication) and homelessness (HR = 6.3); shorter-term heroin use (HR = 5.3); social network influence (exposure) and physically abused (HR = 4.7); friends approve/condone drug injecting (HR = 3.5); lower perceived social distance from injectors (HR = 2.9); and younger age at first heroin use (HR = 1.2). Independent predictors among former-injectors were social network influence (communication) and lower perceived social distance from injectors (HR = 3.4); white race/ethnicity (HR = 2.0); not very afraid of needles (HR = 1.8); and younger age (HR = 1.1). Conclusions: The risk of initiating injecting was lower than the risk of resuming injecting. Social network influence facilitates transitioning to injecting among those susceptible. Interventions to prevent injecting should address both social network influence and individual susceptibility.

Syringe-mediated drug sharing among injecting drug users: Patterns, social context and implications for transmission of blood-borne pathogens

Drug injectors are at risk for infection with human immunodeficiency virus (HIV) and other blood-borne pathogens through the exchange of (infected) blood resulting from unhygienic injecting practices. Research attention and public discussion have focused primarily on the sharing of syringes and needles. While the focus on syringe sharing has sparked important interventions (bleach distribution, syringe exchange) it may have obscured the social relationship in which injecting equipment is used. Drug sharing plays a crucial role in the social organization of the drug using subculture. In this paper, various drug sharing practices and other distinguishable aspects of the injecting process-collectively termed Syringe-Mediated Drug Sharing (SMDS)-are described. All of these behaviors may put injecting drug users (IDUs) at risk for infection. The purpose of this paper is to stimulate scientific inquiry into SMDS behaviors and the social contexts which shape them. Descriptions are based primarily on field studies in Rotterdam and New York City. Recommendations for safer injecting training and education are proposed, as are directions for future research.

Networks, resources and risk among women who use drugs

The public health tradition of intervening at the environmental level has not been fully exploited in terms of HIV prevention efforts among drug users. Women who use drugs are at particularly high risk of acquiring HIV and other blood borne and sexually transmitted infections, such as hepatitis B (HBV) and hepatitis C (HCV), and could potentially benefit from environmental level interventions. In a review of the existing literature, we examine the extent to which the linkages among multiple causal levels may contribute to the disease transmission risk experienced by women who use drugs. The multiple causal levels of risk potentially involved in the transmission dynamics of infectious pathogens include biological, behavioral, dyadic relationship, network, and structural levels. Biological and behavioral risk factors have already been examined in depth; yet, little empirical research currently exists for other causal levels. Increasingly, investigators suggest that the character and dynamics of relationships with sex partners may be an important determinant of risk, both for engaging in risk behaviors and for doing so with high-risk partners. The influence of higher-order causal level factors, specifically network and structural factors, are the least well documented, but are posited to be a principal underlying cause of the current differential HIV incidence rates between men and women who use drugs. Future research should focus on these higher-order causal levels, in order to better understand disease transmission dynamics; to better evaluate the limitations, as well as the opportunities, of current intervention efforts; to develop interventions that improve and supplement current HIV prevention efforts among women who use drugs; and to inform public policy debate.

Risk correlates of prevalent HIV, hepatitis B virus, and hepatitis C virus infections among noninjecting heroin users.

OBJECTIVE To examine lifetime correlates of HIV and hepatitis B and C (HBV and HCV) infections among noninjecting heroin users (NIUs). METHODS Between March 1996 and March 2001, 483 eligible NIUs were tested for HIV, HBV, and HCV antibodies and administered structured interviews. Multivariate logistic regression analyses were stratified by injecting history. RESULTS Among never-injectors (69.8%), significant (p <.05) correlates were unprotected sex with men who have sex with men (HIV and HBV), unprotected sex with NIUs (HIV), self-reported syphilis infection (HBV), longer duration of heroin use (HBV and HCV), shorter duration of cocaine use (HIV), blood transfusion before 1986 (HIV), and having been tattooed (HCV). Among former injectors (30.2%), significant correlates were receptive syringe sharing (HIV and HBV), frequent lifetime injection (HCV), longer duration of sexual activity (HBV), and having been tattooed (HCV). CONCLUSION Never-injectors infected with HIV and HBV appear to have become infected mainly through sexual transmission, whereas former injectors appear to have become infected with HIV and HCV mainly though injecting risk and with HBV through both injecting and sexual risk. Interventions targeted at NIUs should prevent unsafe sex as well as the initiation or resumption of injecting. In addition, unhygienic tattooing, which may lead to HCV exposure, should be a focus of prevention efforts.

Risk networks and racial/ethnic differences in the prevalence of HIV infection among injection drug users

Studies among injection drug users (IDUs) find a higher prevalence of HIV infection among black and Puerto Rican IDUs than among white IDUs. Risk behaviors seldom explain these differences. We examine how risk networks contribute to racial/ethnic variations in HIV prevalence. Six hundred sixty-two IDUs were recruited on the street in Bushwick (New York City), interviewed, and tested for HIV. Risk behaviors and networks were analyzed to explain racial/ethnic variations in HIV. Forty percent of IDUs were infected with HIV. HIV prevalence was greater for Puerto Ricans (45%) and blacks (44%) than for whites (32%). Egocentric sexual and drug risk networks were predominantly racially/ethnically homogeneous. After multivariate adjustments for risk behaviors and risk networks, black-white differences in HIV prevalence were no longer significant. Although differences between Puerto Ricans and whites persisted, post hoc analyses suggested that network partner characteristics might explain these differences. In Bushwick, racially/ethnically discordant risk partnerships involving black IDUs may function as potential bridges of transmission between groups.

Street-level drug markets: Network structure and HIV risk

Abstract Ethnographic and formal social network methods are used to define and situate three categories of injecting drug users - a core, an inner periphery and an outer periphery - in a street-level drug market scene. Different locations in these network structures are shown to be associated with different levels of AIDS risk behaviors and of HIV infection rates. A network perspective helps to understand HIV risks and to devise appropriate interventions.

Risk behavior and HIV infection among new drug injectors in the Era of AIDS in New York City

OBJECTIVE To examine HIV risk behavior and HIV infection among new initiates into illicit drug injection in New York City. DESIGN AND METHODS Cross-sectional surveys of injecting drug users (IDUs) recruited from a large detoxification treatment program (n=2489) and a street store-front research site (n=2630) in New York City from 1990 through 1996. Interviews covering demographics, drug use history, and HIV risk behavior were administered; serum samples were collected for HIV testing. Subjects were categorized into two groups of newer injectors: very recent initiates (just began injecting through 3 years) and recent initiates (injecting 4-6 years); and long-term injectors (injecting > or = 7 years). RESULTS 954 of 5119 (19%) of the study subjects were newer injectors, essentially all of whom had begun injecting after knowledge about AIDS was widespread among IDUs in the city. New injectors were more likely to be female and white than long-term injectors, and new injectors were more likely to have begun injecting at an older age (median age at first injection for very recent initiates, 27 years; median age at first injection for recent initiates, 25 years; compared with median age at first injection for long-term injectors, 17 years). The newer injectors generally matched the long-term injectors in frequencies of HIV risk behavior; no significant differences were found among these groups on four measures of injection risk behavior. HIV infection was substantial among the newer injectors: HIV prevalence was 11% among the very recent initiates and 18% among the recent initiates. Among the new injectors, African Americans, Hispanics, females, and men who engaged in male-male sex were more likely to be infected. CONCLUSIONS The new injectors appear to have adopted the reduced risk injection practices of long-term injectors in the city. HIV infection among new injectors, however, must still be considered a considerable public health problem in New York City.