Drug Users In Amsterdam Research Articles

Surveillance cultures, chains and holes in street level networking: dealing with drug users in Amsterdam (Netherlands) and Porto Alegre (Brazil)

If surveillance is understood as a complex multi-dimensional process, then collaboration between health, social and law enforcement sectors can be viewed as a part of the surveillance culture of particular societies and urban settings. Policies towards illicit drugs usually build on a two-track approach—public health and public order—with different objectives that have to be negotiated daily by street level workers in the light of their differing beliefs on drug use. This paper brings examples of collaboration and non-collaboration among workers from social, health and law enforcement agencies in Amsterdam, the Netherlands, and Porto Alegre, Brazil in their daily interactions with drug users, to analyze the types of surveillance arising from these negotiations. The study utilizes results from 80 in-depth interviews with street level workers and 800 hours of participant observation carried out from February 2010 until March 2011, equally divided between the two cities. Different cultures of surveillance produce diverse state-citizen approaches in terms of coercion, care, and rights. In Amsterdam, close collaboration and information exchange among workers produce a ‘chain’ surveillance culture: an intensive screening allows drug users to have more access to care, yet, at the same time this can produce excessive control over users’ lives. In Porto Alegre, by contrast, insufficient collaboration produces a surveillance culture of ‘holes’: less systematic screening and lack of information sharing allows users to slip out of care, and of workers’ surveillance sight. Historically, though coming from apparently opposite extremes in terms of drug surveillance (respectively permissive and controlling), both Amsterdam and Porto Alegre in practice show surveillance cultures which combine care and order. Combinations, however, vary according to different assemblages between actors concerned with transforming drug users’ lives.

Drug Users in Amsterdam: Are They Still at Risk for HIV?

Background and AimsTo examine whether drug users (DU) in the Amsterdam Cohort Study (ACS) are still at risk for HIV, we studied trends in HIV incidence and injecting and sexual risk behaviour from 1986 to 2011.MethodsThe ACS is an open, prospective cohort study on HIV. Calendar time trends in HIV incidence were modelled using Poisson regression. Trends in risk behaviour were modelled via generalized estimating equations. In 2010, a screening for STI (chlamydia, gonorrhoea and syphilis) was performed. Determinants of unprotected sex were studied using logistic regression analysis.ResultsThe HIV incidence among 1298 participants of the ACS with a total follow-up of 12,921 person-years (PY) declined from 6.0/100 PY (95% confidence interval [CI] 3.2–11.1) in 1986 to less than 1/100 PY from 1997 onwards. Both injection and sexual risk behaviour declined significantly over time. Out of 197 participants screened for STI in 2010–2011, median age 49 years (IQR 43–59), only 5 (2.5%) were diagnosed with an STI. In multivariable analysis, having a steady partner (aOR 4.1, 95% CI 1.6–10.5) was associated with unprotected sex. HIV-infected participants were less likely to report unprotected sex (aOR 0.07, 95% CI 0.02–0.37).ConclusionsHIV incidence and injection risk behaviour declined from 1986 onwards. STI prevalence is low; unprotected sex is associated with steady partners and is less common among HIV-infected participants. These findings indicate a low transmission risk of HIV and STI, which suggests that DU do not play a significant role in the current spread of HIV in Amsterdam.

Low incidence of reinfection with the hepatitis C virus following treatment in active drug users in Amsterdam

More than two-thirds of hepatitis C virus (HCV) infections are associated with injecting drug use. Despite the wide availability of standard treatment with pegylated interferon and ribavirin, active drug users (DU) have limited access to HCV treatment. Physicians may be reluctant to prescribe treatment because of the presumed high risk of reinfection. However, data on reinfection in treated DU remain scarce. Active DU with chronic HCV infection were treated in a multidisciplinary setting. After achieving a sustained virologic response, patients were tested at 6-12-monthly intervals for HCV RNA. To distinguish between relapse and reinfection, sequence and phylogenetic analyses were performed on the NS5B region of the HCV genome. The incidence of reinfection was calculated using person-time techniques. From April 2005 to March 2010, 69 active DU treated for HCV had sufficient follow-up, median 2.5 years (interquartile range, 1.6-3.7). Sustained virologic response was achieved in 42 patients (61%). During follow-up, 41 patients remained HCV RNA-negative; of these, two patients died. During treatment, five out of 41 injected drugs, which increased to 11 out of 41 after the end of treatment. One case of reinfection was observed, followed by spontaneous clearance of the virus. The overall incidence was 0.76/100 person-years (95% confidence interval 0.04-3.73). For only those individuals reporting injecting drug use, the incidence was 3.42/100 person-years (95% confidence interval 0.17-16.90). We report a low incidence of HCV reinfection following treatment in DU participating in a multidisciplinary programme. Active drug use, including injecting, should not preclude access to treatment for HCV.

The effect of hepatitis C treatment and human immunodeficiency virus (HIV) co‐infection on the disease burden of hepatitis C among injecting drug users in Amsterdam

The hepatitis C virus (HCV) disease burden among injecting drug users (IDUs) is determined by HCV incidence, the long latency period of HCV, competing mortality causes, presence of co-infection and HCV treatment uptake. We examined the effect of these factors and estimated the HCV disease burden in Amsterdam. A Markov model was developed, incorporating HCV and human immunodeficiency virus (HIV), and parameterized with data from the Amsterdam Cohort Studies, surveillance studies and literature. IDU population of Amsterdam. HCV infection simulated from its acute phase to HCV-related liver disease (i.e. decompensated cirrhosis and hepatocellular carcinoma). The HCV prevalence among IDUs in Amsterdam increased to approximately 80% in the 1980s. From 2011 to 2025, the HCV-related disease prevalence will accordingly rise by 36%, from 57 cases (95% range 33-94) to 78 (95% range 43-138), respectively. In total, 945 (95% range 617-1309) individuals will develop HCV-related liver disease. This burden would have been 33% higher in the absence of HIV, resulting in 1219 cases (95% range 796-1663). In Amsterdam, 25% of HIV-negative IDUs receive successful HCV treatment, reducing the cumulative disease burden by 14% to 810 (95% range 520-1120). Further reduction of 36% can be achieved by improving treatment, resulting in 603 cases (95% range 384-851). The hepatitis C virus burden among injecting drug users in Amsterdam has been reduced by a high competing mortality rate, particularly caused by HIV infection, and to a smaller extent by hepatitis C virus treatment. Improved hepatitis C virus treatment is expected to contribute to reduce the future hepatitis C virus disease burden.

Harm reduction intensity—Its role in HAART adherence amongst drug users in Amsterdam

BackgroundOpioid substitution treatment seems to improve adherence to highly active antiretroviral therapy (HAART) in drug users (DU). DU in Amsterdam receive methadone within a harm reduction programme. We hypothesized that not only receiving methadone, but joining this complete comprehensive programme would improve HAART adherence. MethodsIncluded were 102 HIV-positive DU attending the Amsterdam Cohort Study (ACS), reporting HAART use at multiple visits between 1999 and 2009. Non-adherence was defined as taking less than 95% of medication in the past 6 months (self-reported). Harm reduction intensity (HR) was measured by combining injecting drug use, methadone dosage and needle exchange, in different levels of participation, ranging from no/incomplete HR, complete HR to low or no dependence on HR. We studied the association between non-adherence and harm reduction intensities with logistic regression models adjusted for repeated measurements. ResultsNon-adherence was reported in 11.9% of ACS visits. Non-injecting DU with low dependence on HR were less adherent than DU with complete HR (aOR 1.78; CI 95% 1.00–3.16), although there was no overall effect of HR. No difference was demonstrated in adherence between DU with complete HR and incomplete HR. Unsupervised housing (no access to structural support at home) (aOR 2.58; CI 95% 1.40–4.73) and having a steady partner (aOR 0.48; CI 95% 0.24–0.96) were significantly associated with respectively more and less non-adherence. ConclusionsIn Amsterdam, still-injecting DU who are exposed to systematic and integrated care, although not practising complete harm reduction, can be just as adherent to HAART as DU who make use of complete harm reduction and non-injecting DU with no dependence on harm reduction. These findings suggest the importance of a systematic and comprehensive support system including supervised housing and social and medical support to increase HAART adherence rates amongst all HIV-infected DU. When such programmes are introduced in settings where injecting drug use is highly prevalent, access to HAART for drug users in these settings can and should be increased.

Hepatitis C testing and treatment among active drug users in Amsterdam

Although hepatitis C virus (HCV) treatment has shown to be effective, uptake of treatment among active drug users is still low. The Drug Users Treatment for Chronic Hepatitis-C project aims to offer active drug users in Amsterdam HCV testing and treatment using a multidisciplinary approach. The study population comprises drug users participating in the Amsterdam Cohort Studies and drug users referred to the Drug Users Treatment for Chronic Hepatitis-C unit. Drug users were offered HCV testing and, if chronically infected, medical and psychiatric screening and HCV treatment. Various specialists collaborated to provide optimal care. We assessed test-uptake and treatment-uptake and outcomes. Four hundred and ninety-seven Amsterdam Cohort Studies drug users were offered HCV testing: 449 out of 497 (90%) accepted. HCV antibodies were found in 267 out of 449 (60%): 183 out of 267 (69%) were HCV-viremic and 49 out of 183 (27%) were HIV-co-infected. Of the 134 HCV-monoinfected patients, 102 (76%) initiated additional medical screening and 44 started treatment by 1 July 2009. Sixty-two drug users referred from methadone clinics were also HCV-monoinfected, of whom 14 started treatment by 1 July 2009. In total 58 persons were treated: 16 (27%) with genotype 1 or 4, 42 (72%) with genotype 2 or 3. Eighty-four percent used methadone, 97% used drugs (heroin, cocaine or amphetamine) at least once in the 6 months before treatment, 19% were active injectors. Sixty-two percent used alcohol, 41% had psychiatric disease other than substance abuse. Of the 57 individuals with sufficient follow-up, 37 (65%) achieved sustained virological response. In a multidisciplinary setting, HIV-negative drug users with chronic HCV infection can be treated successfully despite active drug or alcohol use and psychiatric diseases. Therefore, access to HCV therapy using an integrated approach should be increased for this population.

Transitions in Drug Use in a New Generation of Problem Drug Users in Amsterdam: a 6-Year Follow-Up Study

Aims: This study describes the transitions in drug use in Amsterdam among young drug users (YDUs) who are inhaling or injecting cocaine or using illicitly obtained opiates. Methods: From 2000 until 2003, 187 YDUs (≤30 years) were recruited of whom 126 were followed into 2007. Results: During the 6 months prior to inclusion, 95% used cocaine, 60% used illicit opiates, and 9% injected more than once a week. During follow-up, the incidence of new-onset heroin use was 4.8/100 person-years. The incidence of injecting was much lower for never-injectors (2.1/100 person-years) than for ever-injectors who relapsed (13.2/100 person-years). Transition to abstinence or nonfrequent drug use is common (23/100 person-years), mostly followed by a relapse (73/100 person-years). Polydrug users were less likely to discontinue their frequent drug use than monodrug users. Conclusions: Treatment services should target the crack cocaine users to prevent further marginalization and, during abstinence, to prevent relapse. Although the prevalence and incidence of injecting are relatively low, it is still an option for opiate users, especially those with a history of injecting.

Frequent HCV reinfection and superinfection in a cohort of injecting drug users in Amsterdam

This study investigates the occurrence of HCV reinfection and superinfection among HCV seroconverters participating in the Amsterdam Cohort Studies among drug users from 1985 through 2005. HCV seroconverters (n=59) were tested for HCV RNA at five different time points: the last visit before seroconversion (t=-1), the first visit after seroconversion (t=1), six months after (t=2) and one year after (t=3) seroconversion, and the last visit prior to November 2005 (t=4). If HCV RNA was present, part of the NS5B region was amplified and sequenced. Additional phylogenetic analysis and cloning was performed to establish HCV reinfection and superinfection. Multiple HCV infections were detected in 23/59 (39%) seroconverters; 7 had HCV reinfections, 14 were superinfected, and 2 had reinfection followed by superinfection. At the moment of HCV reinfection, 7/9 seroconverters were HIV-negative: persistent HCV reinfection developed in both HIV-positive cases but also in 4/7 HIV-negative cases. In total, we identified 93 different HCV infections, varying from 1 to 4 infections per seroconverter. Multiple HCV infections were observed in 10/24 seroconverters with spontaneous HCV clearance (11 reinfections, 3 superinfections) and in 13/35 seroconverters without viral clearance (20 superinfections). HCV reinfection and superinfection are common among actively injecting drug users. This might further complicate the development of an effective HCV vaccine.

Two decades of hepatitis B infections among drug users in Amsterdam: Are they still a high‐risk group?

In general, little is known about the incidence of hepatitis B virus (HBV) among drug users, especially among non-injecting drug users. Therefore, changes in incidence, risk factors, and circulating genotypes over time were determined among drug users in Amsterdam over an 18-year period (1985-2002). Sera of 1,268 drug users, both injecting and non-injecting, were screened for anti-HBc. HBV genotypes of the anti-HBc seroconverters were determined. Poisson regression was used to test for temporal trends in incidence and to identify risk factors for seroconversion. Of the 598 participants who were anti-HBc negative at entry, 83 seroconverted for anti-HBc. The incidence of HBV declined from 5.9/100 Person Years up to 1993 to 0/100 Person Years in 2002. Of the drug users infected acutely, both injecting and non-injecting, 88% were infected with the same genotype D, serotype ayw3 strain. Multivariate analyses revealed current injecting, age, and calendar year of visit as independent risk factors. The decline in the incidence of HBV among drug users in Amsterdam is probably caused by a decline in injecting behavior. Injecting and non-injecting drug users were infected with the same strain, indicating that drug users infect one another, regardless of their risk behavior. After 2000, no injecting drug users with an acute HBV infection were reported to the Public Health Service Amsterdam and the specific genotype D strain had disappeared. These findings suggest that drug users may no longer be a high-risk group for HBV infection in Amsterdam. However, trends in drug use need to be monitored.

P.029 Two decades of hepatitis B infections among drug users in Amsterdam: are they still a high-risk group?

Purpose: The occurrence of HIV-1 dual infections in Amsterdam, The Netherlands, was examined from 2003–2007 to investigate whether or not HIV-1 dual infections are increasing as the number of HIV-1 infected individuals increased here over this time period. Methods: All first HIV-1 genotyping sequences determined between 2003 and 2007 were retrieved and examined for the number of degenerate base codes in the RT fragment. From a total of 73 patients with a degenerate base code count of > 33, a fragment of the V3-V4 region of the env gene was amplified, cloned and sequenced to verify the presence of a HIV-1 dual infection. Dual infections were counted for each year investigated. Results: No significant change in incidence of dual infections was seen in our patient population selected upon the degenerate base count in the HIV-1 genotyping sequence from 2003 till 2007. The frequency of HIV-1 dual infections varied between 1.0%–2.8%/year, with no significant trend in time (p = 0.49). Based upon the number of patients with a high degenerate base code count, an increase in dual infections was expected in 2006 and 2007, but this was not observed. HIV-1 dual infections were similar to HIV-1 single infections in The Netherlands in distribution by risk group, gender and subtype. Conclusion: HIV-1 dual infections in The Netherlands are not increasing from 2003 to 2007 although the HIV-1 infected population is expanding in this period.

Estimating the Total Mortality Among Problem Drug Users

This paper's objective is to develop a method to estimate the total mortality among problem drug users. The total mortality is given by a base rate of mortality not related to drugs and the deaths that are directly and indirectly related to drugs. A fatal poisoning by drugs (overdose) is directly related to drugs, whereas a casualty due to a drug-related disease or a drug-related accident is indirectly related to drugs. As an example of a method to estimate the total mortality, the results from a cohort study among methadone patients in Amsterdam were projected on the whole population of problem drug users in The Netherlands. Due to differences between the problem drug users in Amsterdam and the rest of the country, adjustments were required. It was found that an initial estimation did not require adjustment for injection behavior and gender but did require adjustment for age and the percentage of HIV infection. In a first unadjusted estimation, the total number of deaths among problem drug users in The Netherlands in 2001 was estimated at 606 deaths. After adjustment for age, the estimated mortality decreased to 573 deaths, and after adjustment for HIV infection, this estimation again decreased to 479 deaths. From the ultimately estimated mortality, 11% was considered to be not related to drugs, 23% was attributed directly to drugs, and 66% was attributed indirectly to drugs. The number of direct deaths, as estimated by this method, falls in the same order of magnitude as the number extracted from the Causes of Death Statistics, when selecting cases according to the Drug-Related Deaths Standard as established by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). Further cross-validation with other measures will be needed to assess the accuracy of the method, the limitations of which are discussed with respect to stipulating directions for future research.

Decline in HIV incidence and injecting, but not in sexual risk behaviour, seen in drug users in Amsterdam: a 19-year prospective cohort study

To study temporal changes in HIV incidence, HIV transmission routes, and both injecting and sexual risk behaviour in the open Amsterdam Cohort Study (ACS) among drug users. Initiated in 1985, the ACS enables us to study changes in trends since HAART became widespread in 1996. Person-time techniques were used to study the trend in HIV incidence among HIV-negative drug users. HIV transmission routes were determined using detailed standardised questionnaires. Trends in injecting and sexual risk behaviours were evaluated with a logistic regression model adjusted for correlations between visits of the same individual. The 1315 HIV-negative individuals, of whom 93 seroconverted for HIV, yielded 6970 HIV-negative person-years of follow-up. The HIV incidence was seven per 100 person-years in 1986 and varied between 0 and 0.5 per 100 person-years after 1999. The odds ratio was 15.6 (95% confidence interval, 2.6-94.6) for HIV transmission through unprotected heterosexual contact versus injecting after 1996 compared with the period before. Reports of both injecting and borrowing needles significantly declined over the period 1985-2004. Reports of sexual risk behaviour and sexually transmitted infections at follow-up visits decreased before 1996, but not after 1996. The HIV incidence among drug users in the ACS has declined since 1985. Accompanied by a reduction in injecting drug use and needle sharing, this decline occurred despite continued sexual risk behaviour. At present, new HIV seroconversions are related mainly to unprotected heterosexual contacts. Therefore, HIV prevention programmes for drug users should pay specific attention to the importance of safe sex practices.

P.242 Hepatitis C screening and treatment among drug users in Amsterdam: an interim analysis of the DUTCH-C project

P.242 Hepatitis C screening and treatment among drug users in Amsterdam: an interim analysis of the DUTCH-C project

Changes in risk behavior and dynamics of hepatitis C virus infections among young drug users in Amsterdam, the Netherlands

To elucidate the character and magnitude of the hepatitis C virus (HCV) epidemic among drug users in Amsterdam, 197 young drug users from the period 2000 to 2004 were compared with 215 counterparts from 1985 to 1989. Although injection risk behavior and HCV seroprevalence decreased sharply over time, HCV seroprevalence remains high (44%) among young drug users who have ever injected. Phylogenetic analysis shows that current HCV infections originate from diversification of strains already circulating in the past, but also from the recent introduction of new subtypes. HCV subtypes 1a and 3a remain the most prevalent among drug users in Amsterdam, but other subtypes such as 4d and 2b have entered the population. In conclusion, both the unpopularity of injecting drug use and the success of prevention campaigns are likely to be responsible for the decline in the seroprevalence of HCV and increased median time to seroconversion. Treatment of those infected chronically, in combination with the continuation of prevention programs, might decrease future HCV transmission.

Amount of self-reported illicit drug use compared to quantitative hair test results in community-recruited young drug users in Amsterdam.

To assess the dose-effect relationship between self-reported drug intake and the concentration of drugs and/or their metabolites in hair and to examine factors that may mediate this relationship. A cohort study among young drug users (YDU) in Amsterdam, the Netherlands, which began in July 2000. At intake, YDU were asked to report their average drug intake over a 2-month period. A hair sample was taken and then analysed for cocaine, benzoylecgonine (BE), morphine, 6-monoacetylmorphine and methadone. Weighted least-squares regression analysis was used to model hair-test results as a function of reported drug use. Subjects were 95 YDU (using cocaine, heroin, methadone and/or amphetamines at least 3 days/week) aged 18-30 residing in Amsterdam in 2000-2001. Of the 95 YDU, one-third were women; mean age was almost 26; 30% had black hair, 33% blond hair and 37% brown hair. Cocaine use was reported by 92%, heroin by 75% and methadone by 64% of participants. All hair samples contained one or more drugs. Crude correlation coefficients between reported drug doses and drug concentrations in hair ranged between 0.45 and 0.59. The multivariate regression analysis showed that, for one or more types of drug, black-haired people, women and non-western European people had relatively high drug concentrations in hair (significant slope effects). The corresponding multivariate correlation coefficients ranged between 0.63 and 0.87. Hair testing can be used to quantify drug use in epidemiological studies, given that factors such as hair colour and sex are taken into account.

HIV prevalence and risk behaviour in young drug users in Amsterdam.

To assess the HIV prevalence and risk behaviour among regular young drug users (YDU) in Amsterdam. Subjects were 282 YDU (using heroin, cocaine, methadone and/or amphetamines at least 3 days/week) aged 30 years or less who participated in a cross-sectional survey in Amsterdam in 1998. Participants were recruited both directly (41%) through healthcare institutions, and indirectly (59%) by referrals from YDU already enrolled. A comparison sample of YDU from the Amsterdam Cohort Study recruited between 1985 and 1989 was used to describe trends in HIV prevalence and risk behaviour. Mean age was 25 years, 22% were women, 39% had at least once injected drugs, and 22% currently injected in 1998. Cocaine was more often used regularly (70%) than heroin (42%). Of the 282 YDU, 21 (7.4%) were infected with HIV. Among those who had injected drugs, HIV prevalence was 16.2%. Among those who had never injected, the prevalence of HIV infection was 1.8%. A history of injecting declined from 83% in 1985-1989 to 56% in 1998. Compared with 1985-1989, the lack of a recent steady partner appeared to be an important risk factor for a positive HIV status among injectors in 1998, whereas borrowing of used needles/syringes was no longer a risk factor. The use of cocaine among YDU is very popular in Amsterdam. A strong decrease in injecting behaviour has taken place, but among those who inject, risk behaviour is still considerable, and HIV infection is still widespread. Preventative activities should be expanded, specifically among YDU.

Pre-AIDS Mortality and Morbidity among Injection Drug Users in Amsterdam and Baltimore: An Ecological Comparison

Mortality and morbidity between injecting drug users in Amsterdam (n= 624) and Baltimore (n = 2,185) are compared to generate a hypothesis about the role of different health care systems and drug user policies (universal care and harm reduction versus episodic care and criminalization, respectively). Overdose/suicide mortality was twofold higher in Amsterdam; no sufficient explanation was found. Other independent “risk factors” for overdose/suicide mortality were recent injecting, polydrug use, and HIV-seropositivity (especially with CD4 count < 200/mm3). High dose methadone maintenance was associated with lower mortality. Incidence of hospitalizations and emergency room visits was substantially lower in Amsterdam, suggesting that higher accessibility to primary care in Amsterdam lowers (inpatient) hospital visits and presumably societal costs.

Differentiation in the Amsterdam methadone dispensing circuit: determinants of methadone dosage and site of methadone prescription.

To evaluate the Methadone Dispensing Circuit in Amsterdam by identifying determinants of methadone dosage and client characteristics in the different types of methadone programmes. Four hundred and forty-four participants of a cohort study of drug users in Amsterdam who had consented to link data of the Central Methadone Register to the cohort data. From 1985 to 1994, methadone dosage increased from 41 to 59 mg/day. The mean methadone dosage was higher for ethnic West Europeans, Germans, older drug users, HIV-positive drug users, those with a longer duration of prostitution, current injectors, those with a longer duration of injecting, longer duration of methadone use, higher frequency of being dispensed methadone and clients of the prostitutes' and foreigners' outpatient clinic. For clients of the general practitioner, at the police station and in prison the methadone dosage was lower. We found different sets of client characteristics in those receiving methadone at the methadone outpost, the methadone bus, the prostitutes' and foreigners' outpatient clinic, the general practitioner and the outdoor addiction clinic. These results indicate that the Amsterdam system is highly differentiated in a way that is largely concordant with the intended general policy on methadone treatment.

Large declines in sexual risk behavior with noncommercial partners among heterosexual injection drug users in Amsterdam, 1989-1995.

Previous studies among injection drug users have reported small or nonexistent reductions in sexual risk behavior with noncommercial partners, and a large potential for further heterosexual spread of human immunodeficiency virus (HIV) is thought to be present. In the present study, a long-term follow-up and detailed data on sexual behavior were available. Trends were determined using data collected at 5,214 visits of 653 heterosexual injection drug users who participated in the Amsterdam Cohort Study in Amsterdam, the Netherlands between April 1989 and May 1995. Analysis accounted for repeated measurements of one individual and the effect of participation in the study itself. The authors observed a large reduction in sexual risk behavior with noncommercial partners that became apparent only after stratification of trends by knowledge of HIV serostatus. Sex with noncommercial partners and inconsistent condom use both decreased, especially among known HIV-positive individuals. Apart from nonrandom condom use, there also was nonrandom mixing (selective partner choice). Because this was like-with-like mixing, the risk for further sexual transmission of HIV is diminished. In future studies, more detailed information on sexual behavior, mixing, and knowledge of serostatus should be collected. HIV-epidemic modelers should incorporate nonrandom condom use and nonrandom mixing to improve forecasting.

Human immunodeficiency virus infection and other risk factors for skin abscesses and endocarditis among injection drug users

Objective: to study incidence rates of and risk factors for skin abscesses at the site of injection and episodes of endocarditis among injection drug users (IDU). Design: A comprehensive, open cohort study of drug users on the natural history of human immunodeficiency virus (HIV) infection. Methods: From 1986 to 1994, injection drug users in Amsterdam were included in the study. Incidence rates of self-reported skin abscesses and verified episodes of endocarditis were calculated. In uni- and multivariate Poisson regression analysis, risk factors for skin abscesses and endocarditis were determined. Results: 521 HIV-seronegative and 237 HIV-seropositive IDU were followed for 1640 person-years. A total of 545 skin abscesses were reported by 269 IDU (incidence 33/100 person-years). HIV infection, female gender, prostitution among females, foreign nationality, injection of heroin and cocaine, a high frequency of injecting, and obtaining syringes through the needle exchange program were independently and positively associated with skin abscesses. During follow-up, 17 verified episodes of endocarditis were observed (incidence 1.3 100 personyears). Endocarditis was independently associated with HIV infection and a previous history of endocarditis. Furthermore, women and IDU with a skin abscess appeared to be at an increased risk for endocarditis. Conclusions: HIV infection is an independent risk factor for skin abscesses and endocarditis. Also, women are at an increased risk for these injection-related infections. Prevention activities, like promotion of skin cleaning, should be directed at those IDU in whom one or more risk factors have been identified.