People and places: behavioral settings and personal network characteristics as correlates of needle sharing

New methods to investigate infectious disease transmission and pathogenesis--Staphylococcus aureus disease in drug users

Staphylococcus aureus is the single most important bacterial pathogen in infections among drug users. It is responsible for several diseases, ranging from superficial cutaneous abscesses to life-threatening intravascular infections. Although the nature of these infections is well described in published work, there is limited understanding of their epidemiology and pathogenesis. This limitation is in part due to the difficulty of studying disease transmission among drug users in the community, and the limitations of the investigative tools that have so far been used. We review the current understanding of the pathogenesis of staphylococcal disease in drug users and argue for the integration of molecular epidemiological techniques and social network methodology to increase our understanding of the basis for the persistence, distribution, and transmission dynamics of S aureus among drug users. Finally, we propose a framework for investigating the transmission of pathogens in community-based settings.

Medical service use and financial charges among opioid users at a public hospital

We examined the prevalence of drug use related infectious complications among opioid using or dependent individuals and service charges associated with medical care received over a 2-year period at a public hospital. A computerized medical record review was used to identify 3147 individuals with diagnoses related to opioid use or dependence. Forty-nine percent of these patients were treated for bacterial infections and 30% presented for treatment of medical problems arising from the effects of the drugs themselves (e.g. drug withdrawal, overdoses, and drug-induced psychiatric symptoms). Mean charges were $13393 for these patients, nearly 2.5 times the average per patient charges for non-opioid using patients during the study period. Patients with diagnoses related to opioid use or dependence comprised 2% of the total patient population for this period, yet accounted for 5% of total charges. Homeless patients were less likely to have used ambulatory services and were more likely than non-homeless patients to have used emergency and inpatient services. Early detection of patients with opioid use or dependence problems, coupled with effective strategies to engage them in ambulatory preventive services, could allow interventions to reduce morbidity and associated charges in this patient population. The findings suggest that health care providers and policy makers consider policies that promote ambulatory care use among opioid users seeking medical care through the public health care system.

Social relationships and intravenous drug use among methadone maintenance patients

This study examined the extent to which social relationships were associated with continued injection drug use and needle sharing among 252 methadone maintenance patients. Logistic regression analyses indicated that drug use was highest among persons who had a substance using live-in partner and among those with more drug-using social relationships. Among injectors, whites and those who had more people present during IV drug use were more likely to share needles, while those with more emotional support were less likely to do so. These findings suggest that personal relationships strongly influence continued injection drug use and that methadone programs should help patients develop social networks of non-users.

Illicit drug use in one's social network and in one's neighborhood predicts individual heroin and cocaine use

PURPOSE

The nature of competing social environmental factors' influence on substance abuse is unclear. A longitudinal study was undertaken to determine the relative power of social network and neighborhood characteristics to predict continuing illicit drug use.

METHODS

Three hundred forty-two inner-city adults with a history of injection drug use were followed for 1 year; their heroin and cocaine use were assessed semiannually. Multiple logistic regression models were fit to determine the degree to which social network and neighborhood characteristics, assessed at baseline, predicted continuing heroin and/or cocaine use throughout the study period.

RESULTS

Two hundred thirty-six (69%) participants reported continuing heroin and/or cocaine use. Drug use by members of the social network was a stronger predictor of participants' continuing drug use (OR = 4.31, 95% CI 2.51 to 7.40) than was a high level of drug-related arrests in the participant's neighborhood (OR = 2.41, 95% CI 1.24 to 4.71), after adjusting for drug treatment and demographic variables. Both seemed to have independent effects on study participants' drug use.

CONCLUSIONS

These findings reiterate the importance of breaking ties with drug-using associates, even for those who reside in high-risk environments. Further work is needed to develop interventions that increase drug users' success in altering social network composition or also treat drug-using network members.

Investigation of a secondary syringe exchange program for homeless young adult injection drug users in San Francisco, California, U.S.A

This study investigated an HIV prevention program for homeless young adult injection drug users (IDUs) that combined a secondary syringe exchange program (SEP) with community-level activities. Homeless young IDUs were recruited from street-based settings in San Francisco, and a structured questionnaire was administered. The secondary SEP operated in a circumscribed geographic area, and for analytic purposes respondents were assigned to the intervention site group if they primarily spent time in this area (n = 67), or the comparison site group if they primarily spent time elsewhere (n = 55). Almost all (96%) intervention site youth had used the secondary SEP in the past 30 days and were significantly more likely to regularly use SEP. In bivariate analysis, comparison site IDUs were more likely to share syringes, reuse syringes, share the cotton used to filter drugs, and use condoms with casual sex partners only inconsistently. In multivariate analysis, comparison site remained positively associated with sharing syringes (adjusted odds ratio [AOR], 3.748; 95% confidence interval [CI], 1.406-9.988), reusing syringes (AOR, 2.769; 95% CI,1.120-6.847), and inconsistent condom use with casual sex partners (AOR, 4.825; 95% CI, 1.392- 16.721). This suggests that the intervention was effective in delivering SEP services to homeless young adult IDUs, and that IDUs who frequented the intervention site had a lower HIV risk than comparison group IDUs.

Networks and tuberculosis: an undetected community outbreak involving public places

After decades of decline in developed countries, there was a resurgence of tuberculosis in the mid-1980s accompanied by increased recognition that this infectious disease has long remained a major public health problem at the global level. New methods from molecular biology, in particular DNA 'fingerprinting' (of Mycobacterium tuberculosis), made it clear that current transmission and recent infection (in contrast to reactivation of earlier, latent infection) were much more significant than previously believed. Studies of tuberculosis outbreaks using these new tools pointed to complex networks through which infection was spreading and highlighted the need for new approaches to outbreak investigation and disease control. In the study reported here a new approach--combining methods from molecular biology, epidemiology and network analysis--was used to examine an outbreak of tuberculosis in Houston, Texas. Initial investigation using conventional strategies revealed few contacts among 37 patients with identical (six-band) DNA (IS6110-based) fingerprints but subsequent research uncovered over 40 places (including many gay bars) to which patients in this outbreak could be linked. Network methods were used to reconstruct an outbreak network and to quantify the relative importance (here, 'betweenness' centrality) of different actors (persons and places) playing a role in the outbreak. The multidisciplinary work provides the basis for a new approach to outbreak investigation and disease control.

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.

Evaluating effectiveness of syringe exchange programmes: current issues and future prospects

Although a large body of international literature has found syringe exchange programmes (SEPs) to be associated with reduced incidence of blood borne pathogens among injection drug users, recent studies have fuelled controversy surrounding SEP effectiveness. Existing studies are observational in nature and have seldom considered ecologic aspects affecting SEP functioning and evaluation. The authors apply concepts from infectious disease epidemiology to discuss the direct and indirect effects of SEP upon the spread of blood borne pathogens in drug users, their social networks and the broader community. Further, the authors discuss social policies, particularly drug control policies, which have directly and/or indirectly limited SEP functioning at local and national levels. A critical review of the literature suggests that biases common to observational studies can account for higher HIV incidence among SEP attenders relative to non-attenders. Strong selection factors often lead high-risk drug users to be over-represented among SEP attenders. Failure to account for these factors and the indirect effects of SEPs can bias interpretations of programme effectiveness. Future SEP evaluations should consider behavioural data, the local ethnographic context, the prevalence of infectious disease in the groups under study and the structural components of SEP that are most and least effective at reducing incidence of blood borne pathogens. Hierarchical models that take into account the ecological dimensions of SEP are recommended as an approach for future studies. Beyond methodologic concerns, the authors discuss social, legal and programmatic obstacles that must be overcome in order to maximise SEP effectiveness.

The end of the line: has rapid transit contributed to the spatial diffusion of HIV in one of Canada's largest metropolitan areas?

The objective of this study is to describe the relationship between socio-demographic characteristics and the geographic distribution of persons with HIV in the metropolitan area surrounding Vancouver, British Columbia. Specifically, we sought to determine the location of persons with HIV and the population based characteristics related to the rate of anti-HIV medication use. In addition, we investigated the relationship between the distribution of persons on anti-HIV medications and the city's monorail "SkyTrain" route. The residences of persons on anti-HIV therapy were linked to Census Tracts. Data from the most recent census were used to create a socio-demographic profile of each geographic area. The spatial relationship between the distribution of persons on anti-HIV therapy and the path of the monorail was assessed by digitizing the SkyTrain route over a digital Census Tract map. Statistical analyses were used to determine the characteristics of Census Tracts associated with the rate of anti-HIV medication use. The overall rate of anti-HIV medication use in the Census Tracts that are within 1 km of SkyTrain was 66 per 100,000 population, whereas the rate was only 22 in the non-proximal Census Tracts. Multivariate analyses indicated that persons on anti-HIV therapy were significantly less likely to reside where there is a higher proportion of the population female, and were more likely to reside in areas with a higher proportion of the population of First Nations or Aboriginal descent, a higher population density, and in areas within 1 km of the SkyTrain route. Our analyses suggest that neither migration, nor a heightened access to therapy explain these findings. The environment surrounding the SkyTrain may have been conducive to the spatial diffusion of HIV, and could be the focus of targeted public health interventions. The mechanisms responsible for the clustering of persons on anti-HIV medications around the SkyTrain require further investigation.

[Drugs, Poverty and HIV: results regarding a provincial needle exchange program in Point de Repères, Quebec]

In this study (n = 200), the characteristics of IDUs participating in a provincial needle exchange program (NEP) for more than 2 years (> 2 years) were compared with those of IDUs having participated for less than 2 years (< or = 2 years). Compared to the < or = 2 years, the > 2 years were more often recipients of welfare (RC: 4.7), especially among the HIV-positive (RC: 62.0); tried quitting drugs more frequently (RC: 3.8); more often recommended the NEP to other IDUs (RC: 3.1); and more often requested being given shelter and longer opening hours (RC: 3.6). These results highlight the urgent need to improve and develop transitional and support services for the > 2 years. Preventive interventions that would reach out to the < or = 2 years where they live should also be implemented in close collaboration with organizations involved in mental health and drug use prevention.

The effect of syringe exchange use on high-risk injection drug users: a cohort study

OBJECTIVE

To determine whether syringe exchange program use is associated with cessation of syringe sharing among high-risk injection drug users.

DESIGN AND METHODS

Between 1992 and 1996, street-recruited injection drug users were interviewed and received HIV testing and counseling semi-annually, as part of a dynamic cohort study. We examined a cohort of 340 high-risk injection drug users for whom two observations, 6-months apart, were available and who reported syringe sharing at the first interview. Multivariate logistic regression analysis was performed to determine the relationship between syringe exchange program use and cessation of syringe sharing, while controlling for confounding factors.

RESULTS

At follow-up interview, 60% (204 of 340) reported quitting syringe sharing. High-risk injection drug users who began using the syringe exchange program were more likely to quit sharing syringes [adjusted odds ratio (AOR), 2.68; 95% confidence interval (CI), 1.35-5.33], as were those who continued using the syringe exchange program (AOR,1.98; 95% CI, 1.05-3.75) in comparison with non-syringe exchange program users, while controlling for confounding factors.

CONCLUSIONS

The initiation and continuation of syringe exchange program use among high-risk injection drug users is independently associated with cessation of syringe sharing. Syringe exchange program use can be an important component in reducing the spread of blood-borne infectious diseases among high-risk injection drug users.

The social determinants of emergency department and hospital use by injection drug users in Canada

OBJECTIVE

The aim of this study was to describe the relationship between sociodemographic characteristics and human immunodeficiency (HIV) status of a cohort of injection drug users (IDUs) on their self-reported health service utilization.

DESIGN

Interviewer-administered questionnaire.

METHODS

IDUs who had injected illicit drugs within the previous month were recruited through street outreach. They underwent serology for HIV-1 and questionnaires on demographics, drug using behaviors, housing status, and health service utilization (hospitalization overnight and emergency department visits) in the previous 6 months. Logistic regression analysis was used to identify independent associations with the use of health services.

RESULTS

Of 1,103 cohort participants, 65% were male, 63% were white, and 23% were HIV positive. Cocaine was the most frequently injected drug used. Almost half (47%) had used health services in the previous 6 months. The following variables were associated independently with health service utilization (adjusted odds ratio; 95% confidence interval): unstable housing, defined as living primarily in a hotel, boarding room, or transition house or on the street in the past 6 months (1.44; 1.11-1.86); female gender (1.45; 1.11-1.89); HIV-positive status (1.43; 1.06-1.92); injection of cocaine (1.50; 1.12-2.02); and primary care I physician visit in past 6 months (1.91; 1.39-2.64).

CONCLUSION

IDUs with unstable housing were more likely to report emergency department and hospital use, which may be a reflection of their disorganized lifestyle or poorer health status. Further studies are required to assess the effect on the health status and health care use of IDUs of interventions that increase the availability of safe, affordable housing.

Do needle exchange programmes increase the spread of HIV among injection drug users?: an investigation of the Vancouver outbreak

OBJECTIVE

An association between needle exchange attendance and higher HIV prevalence rates among injecting drug users (IDU) in Vancouver has been interpreted by some to suggest that needle exchange programmes (NEP) may exacerbate HIV spread. We investigated this observed association to determine whether needle exchange was causally associated with the spread of HIV.

DESIGN AND METHOD

Prospective cohort study of 694 IDU recruited in the downtown eastside of Vancouver. Subjects were HIV-negative at the time of recruitment and had injected illicit drugs within the previous month.

RESULTS

Of 694 subjects, the 15-month cumulative HIV incidence was significantly elevated in frequent NEP attendees (11.8+/-1.7 versus 6.2+/-1.5%; log-rank P = 0.012). Frequent attendees (one or more visits per week) were younger and were more likely to report: unstable housing and hotel living, the downtown eastside as their primary injecting site, frequent cocaine injection, sex trade involvement, injecting in 'shooting galleries', and incarceration within the previous 6 months. The Cox regression model predicted 48 seroconversions among frequent attendees; 47 were observed. Although significant proportions of subjects reported obtaining needles, swabs, water and bleach from the NEP, only five (0.7%) reported meeting new friends or people there. When asked where subjects had met their new sharing partners, only one out of 498 respondents cited the needle exchange. Paired analysis of risk variables at baseline and the first follow-up visit did not reveal any increase in risk behaviours among frequent attendees, regardless of whether they had initiated drug injection after establishment of the NEP.

CONCLUSIONS

We found no evidence that this NEP is causally associated with HIV transmission. The observed association should not be cited as evidence that NEP may promote the spread of HIV. By attracting higher risk users, NEP may furnish a valuable opportunity to provide additional preventive/support services to these difficult-to-reach individuals.

Psychosocial histories, social environment, and HIV risk behaviors of injection and noninjection drug using homeless youths

Injection drug use is a common risk behavior for HIV infection among homeless, runaway and street youths. However, the psychosocial histories and current social environment of these youths are not well understood. The authors recruited 186 homeless, runaway and street youths using systematic street-based sampling methods, and assessed psychosocial histories, current daily activities, and sexual and drug-related risk behaviors using qualitative and quantitative techniques. Youths reported high lifetime rates of injection drug use (45%), recent drug and alcohol use (100%), and current homelessness (84%). Injection drug using youths were more likely than noninjection drug using youths to report traumatic psychosocial histories, including parental substance use and forced institutionalization, use of alcohol and other noninjection drugs, a history of survival sex, and the use of squats or abandoned buildings as shelter. These findings underscore the need for multifaceted service and prevention programs to address the varied needs of these high-risk youths.

Needle exchange is not enough: lessons from the Vancouver injecting drug use study

OBJECTIVE

To describe prevalence and incidence of HIV-1, hepatitis C virus (HCV) and risk behaviours in a prospective cohort of injecting drugs users (IDU).

SETTING

Vancouver, which introduced a needle exchange programme (NEP) in 1988, and currently exchanges over 2 million needles per year.

DESIGN

IDU who had injected illicit drugs within the previous month were recruited through street outreach. At baseline and semi-annually, subjects underwent serology for HIV-1 and HCV, and questionnaires on demographics, behaviours and NEP attendance were completed. Logistic regression analysis was used to identify determinants of HIV prevalence.

RESULTS

Of 1006 IDU, 65% were men, and either white (65%) or Native (27%). Prevalence rates of HIV-1 and HCV were 23 and 88%, respectively. The majority (92%) had attended Vancouver's NEP, which was the most important syringe source for 78%. Identical proportions of known HIV-positive and HIV-negative IDU reported lending used syringes (40%). Of HIV-negative IDU, 39% borrowed used needles within the previous 6 months. Relative to HIV-negative IDU, HIV-positive IDU were more likely to frequently inject cocaine (72 versus 62%; P < 0.001). Independent predictors of HIV-positive serostatus were low education, unstable housing, commercial sex, borrowing needles, being an established IDU, injecting with others, and frequent NEP attendance. Based on 24 seroconversions among 257 follow-up visits, estimated HIV incidence was 18.6 per 100 person-years (95% confidence interval, 11.1-26.0).

CONCLUSIONS

Despite having the largest NEP in North America, Vancouver has been experiencing an ongoing HIV epidemic. Whereas NEP are crucial for sterile syringe provision, they should be considered one component of a comprehensive programme including counselling, support and education.