Surveillance of HIV infection and related risk behaviour in European prisons. A multicentre pilot study.

BACKGROUND: In order to demonstrate the feasibility of human immunodeficiency virus (HIV) infection and related risk behaviour surveillance in European prisons, a multicentre pilot study was undertaken. METHODS: A cross-sectional survey was carried out in six European prisons (France, Germany, Italy, The Netherlands, Scotland and Sweden). Inmates were invited to complete a self-administered and anonymous questionnaire and to give a saliva sample in order to test for HIV antibodies. RESULTS: Eight hundred and forty-seven out of 1,124 inmates participated in the survey (response rate 75%). Saliva from 817 inmates (73%) was collected and processed for HIV antibodies. Twenty-seven per cent reported that they had ever injected drugs and 49% of these reported they had injected whilst in prison. Eighteen per cent of inmates reported that they had been tattooed whilst in prison, which was found to be higher among injecting drug users (IDUs). One and sixteen per cent reported that they had ever had homosexual and heterosexual intercourse in prison respectively. The HIV prevalence among IDUs was 4% (versus 1% among non-IDUs) (p = 0.02). The proportions of inmates previously tested for hepatitis C and vaccinated against hepatitis B were 24 and 16% respectively. CONCLUSION: This survey demonstrates the feasibility of cross-sectional surveys in European prison inmates and highlights the importance of surveillance of HIV prevalence and related risk behaviour among inmates. The continuing high HIV prevalence and potential for HIV spread in prisons should encourage decision makers in implementing or enhancing harm reduction and education programmes and substance abuse treatment services in prison.

The validity of drug users' self-reports in a non-treatment setting: prevalence and predictors of incorrect reporting methadone treatment modalities.

BACKGROUND: Epidemiological studies among drug users are often based on retrospective self-reports. However, among others, memory failure, being under the influence of drugs, psychopathology, misunderstanding of questions and socially desirable answering may generate inaccurate reporting. METHODS: This study validated self-reported current (methadone dosage) and medium-term (main location of methadone dispensing and frequency of methadone programme attendance over the previous 4-6 months) aspects of methadone treatment in the Amsterdam AIDS cohort study among drug users, using data of the Central Methadone Register. In addition to descriptive measures, logistic regression analysis was used (adjusted for intra-individual correlation) to identify subgroups with incorrect reporting. Data collected at 4406 visits of 505 cohort participants were analysed. RESULTS: Current methadone dosage was accurately reported (unweighted kappa [kappa]: 0.94, weighted kappa [kappa W]: 0.97). A low methadone dosage, short duration of school education and depressive or euphoric mood during the interview were significant and independent predictors of incorrect reporting of methadone dosage. For main location of dispensing kappa was 0.82, for frequency of programme attendance kappa was 0.53 and kappa W 0.87. There was a tendency to reporting the extreme answering categories. Infrequent programme attendance was the only significant predictor of incorrectly reporting frequency of programme attendance. CONCLUSIONS: Drug users are able to give valid self-reports in a setting where social desirability does not play an important role. The main reasons of incorrect reporting were impaired cognitive functioning, memory failure and misunderstanding of questions.

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.

AIMS: To evaluate the Methadone Dispensing Circuit in Amsterdam by identifying determinants of methadone dosage and client characteristics in the different types of methadone programmes. DESIGN AND PARTICIPANTS: 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. FINDINGS: 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. CONCLUSIONS: 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.

High rates of drug use, but low rates of HIV risk behaviours among injecting drug users during incarceration in Dutch prisons.

AIMS: To determine levels of injecting drug use and sexual risk behaviours in injecting drug users during and immediately following imprisonment in The Netherlands. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional survey of drug injectors attending methadone clinics, a sexually transmitted disease clinic and a central research site in Amsterdam. The mean age of the 188 participants was 35 years, 78% were male and 34% had HIV antibodies. MEASUREMENTS: Self-reported drug use and sexual behaviours during the last period of imprisonment in Dutch prisons within the previous 3 years and injecting drug use in the week following release from prison. FINDINGS: A period of imprisonment in the preceding 3 years was reported by 188 (41%) of 463 interviewed drug injectors. The mean duration of last imprisonment was 3.6 months. Any use of cannabis, heroin or cocaine during imprisonment was reported by 55%, 37% and 20%, respectively. Five injectors (3%) admitted to having injected in prison, but no sharing of needles and syringes was reported. Vaginal or anal sex was reported by two (1%) of the men and none of the women. Relapse to drug injecting during the week following release from prison was reported by 78/186 (42%) participants, in most cases (34%) at the very first day of release. Drug use behaviours during imprisonment were similar for those who were designated current injectors at the time of imprisonment and those who were not, but injecting in the first week following release from prison was far higher among 'current' injectors (63%) than among those who were not (11%). CONCLUSIONS: Contrary to findings from other countries, low levels of HIV risk behaviours occur among imprisoned drug injectors in The Netherlands. Intra-prison HIV preventive measures should be considered taking into account the nationally, regionally or locally varying conditions within the existing prisons.

Estimating the size of the HIV epidemic among injecting drug users in Amsterdam.

Aim of this study was to assess the cumulative incidence of HIV-infection, AIDS and pre-AIDS death in the population of injecting drug users (IDU) in Amsterdam. By assuming equivalence, between a cohort of IDU and the IDU population, of the ratios of incidences of AIDS and pre-AIDS death to the number of HIV positive persons giving rise to these incidences, the numbers of HIV positive persons and pre-AIDS deaths in the population could be calculated, given that other parameters were known. Cohort study data on HIV prevalence and incidences of HIV infection, AIDS, and pre-AIDS death, were combined with national AIDS surveillance data. As of 1 October 1994, the estimated cumulative number of HIV positive IDU in Amsterdam was approximately 1280, far higher than a recent back-calculation estimate. Of the 1280, 204 HIV positive IDU had been diagnosed with AIDS, while about 270 had died pre-AIDS. The HIV prevalence of IDU residing in Amsterdam that were still alive and free of AIDS was hence estimated at around 800. Since the incidence of pre-AIDS death and AIDS exceeded the number of seroconversions during the past four years, the HIV epidemic among IDU in Amsterdam appears to be dwindling. A lower bound of the number of HIV positive IDU being alive, AIDS-free and living elsewhere in the Netherlands was roughly estimated at 600. Because of untimely deaths, only a limited number of HIV positive IDU can be expected to be diagnosed with AIDS in the future. Since these estimates are based upon some rather bold assumptions, they should be interpreted with caution and require further validation by independent sources.

[Little HIV risk behavior in drug users during detention in Dutch penitentiaries]. / Weinig HIV-risicogedrag bij drugsgebruikers tijdens detentie in Nederlandse strafinrichtingen.

OBJECTIVE: To assess levels of HIV risk behaviour in injecting drug users during and immediately following prison terms in the Netherlands. DESIGN: Descriptive. SETTING: Municipal Health Service, Amsterdam, the Netherlands. METHODS: Injecting drug users taking part in a follow-up study on HIV infection were interviewed on injecting drug use and vaginal and anal sexual contact during their last prison term in the 3 years preceding the interview and on injecting drug use in the week following release from prison. RESULTS: A prison term in the preceding 3 years was reported by 188 (41%) of 463 interviewed drug injectors. The mean age of the 188 was 35.5 years: 146 (78%) were males, 63 (34%) had HIV antibodies, and the mean duration of latest prison term was 3.6 months. Some use of cannabis, heroin, or cocaine in prison was reported by 104 (55%), 69 (37%), and 38 (20%) respectively. Five injectors (3%) reported having injected in prison: in 4 cases once and in 1 case 3 times. No sharing of needles and syringes was reported. Vaginal or anal sex was reported by 2 (1%) of the men and none of the women. Relapse to drug injecting during the week following release from prison was reported by 78/186 (42%) participants, in most cases (34%) on the very day of release. CONCLUSION: Contrary to findings from other countries, low levels of HIV risk behaviour occur among imprisoned drug injectors in the Netherlands. Although noninjecting drug use in prison is common, drug injecting and the sharing of injecting equipment is rare. There appear to be no grounds for making clean needles and syringes available in Dutch prisons.

The impact of drug users on inpatient hospital care during the human immunodeficiency virus epidemic in Amsterdam.

BACKGROUND: As a consequence of the human immunodeficiency virus (HIV) epidemic, which continues among illicit drug users, high rates of HIV-associated morbidity are believed to exist. This study focuses on hospitalizations of drug users and on the relative contribution of drug users to the total burden of inpatient hospital care in Amsterdam. METHODS: During the years 1990-1992, data were collected on hospital admissions of injecting and non-injecting drug users to all 10 general and university hospitals in the city of Amsterdam (population 700 000; estimated number of drug users 5800). Total number of admissions, total days of hospitalization and primary discharge diagnoses according to HIV serostatus and sex were determined for drug users. RESULTS: A total of 1293 admissions were recorded among 842 hospitalized drug users. Between 53% and 77% of days of hospitalization attributable to drug users related to HIV-infected patients, and at least 23% to patients with AIDS. In the 20-44 age group of the Amsterdam population, 5.1% of days of hospitalization for men and 1.8% for women could be attributed to drug users, or about twice as much as could be expected from their numbers alone. For all ages, the contribution of drug users to hospitalizations was 1.2% for males, 0.4% for females, and 0.8% for all. Drug users occupied an average of 19 hospital beds, corresponding to an annual cost of US$ 3.1 million. Due to underreporting of admissions, these figures should be considered lower bound estimates. CONCLUSIONS: On the total scale of inpatient hospital expenditure in Amsterdam, the contribution of illicit drug users appears to be small.

Predictors of mortality in the Amsterdam cohort of human immunodeficiency virus (HIV)-positive and HIV-negative drug users.

The impact of human immunodeficiency virus (HIV) infection and other risk factors on mortality was studied in a cohort of Dutch injection drug users and drug users who did not inject. Participants were recruited between 1985 and 1992 and followed up through 1993. Vital status was ascertained through repeat visit information, supplemented by population register data. A total of 77 deaths were recorded among 632 drug users, for a mortality rate per 1,000 person-years of 7 for HIV-negative noninjection drug users, 18 for HIV-negative injection drug users, and 64 for HIV-positive injection drug users. In multivariate analyses, limited to injection drug users, a positive HIV serostatus, age above 40 years, and using benzodiazepines several times daily were significantly associated with an elevated risk of death, both for death from all causes and for death preceding acquired immunodeficiency syndrome (AIDS) diagnosis (pre-AIDS). For pre-AIDS death, the adjusted relative risk associated with HIV infection was 2.2 (95% confidence interval 1.3-3.7). Only 38% of HIV-infected injection drug users who died were diagnosed with AIDS. However, 76% of HIV-infected injection drug users who died without AIDS diagnosis had evidence of immunosuppression (CD4 count < 500/microliters). Daily use of methadone and participation in needle and syringe exchange schemes were not associated with lower mortality rates. This study illustrates in a group of injection drug users with a 30% HIV seroprevalence and a high background mortality the profound influence on mortality that HIV infection has gained.

Death from suicide and overdose among drug injectors after disclosure of first HIV test result.

OBJECTIVE: To investigate whether notifying injecting drug users (IDU) of their positive HIV serostatus contributes to suicide and overdose mortality risk. DESIGN: Members of a cohort of IDU, recruited since December 1985, who first learned their HIV serostatus after study entry but before December 1992, were studied for incidence of deaths due to suicide and overdose. METHODS: Incidence of mortality due to suicide/overdose was calculated from date of first HIV test result disclosure until the end of follow-up or diagnosis of AIDS. RESULTS: Eighty-six HIV-positive and 252 HIV-negative IDU were included with median follow-up times of 4.3 and 4.0 years, respectively. Seven suicides and 10 deaths from overdose were recorded. High suicide/overdose risk shortly after test result notification was not found among HIV-positive IDU. Only one out of eight HIV-positive IDU who died of suicide/overdose died within 6 months of first disclosure. The overall suicide/overdose mortality rate was higher for HIV-positive than HIV-negative IDU; the rate ratio being 2.46 [95% confidence interval (CI), 0.95-6.39] or 2.04 (95% CI, 0.77-5.39) after control for confounders. CONCLUSIONS: Notifying IDU of their positive HIV serostatus does not appear to lead to a sudden and substantial rise in suicide/overdose deaths. Although death from suicide/overdose is more common among HIV-positive than HIV-negative IDU, this difference is likely to result from factors other than test result disclosure. Therefore, provided that appropriate counselling is offered, we see no reason to discourage voluntary HIV test result notification for fear of inducing suicide in HIV-infected IDU.

Hepatitis B virus infection in a group of heterosexuals with multiple partners in Amsterdam, The Netherlands: implications for vaccination?

The aim of the study was to assess prevalence and incidence of hepatitis B virus (HBV) infection among heterosexual men and women with multiple partners attending a sexually transmitted disease (STD) clinic and to establish risk factors of HBV infection in order to consider immunisation for those subjects. A prospective study of heterosexual men and women selected on having multiple partners and presenting to an STD clinic as new patients was carried out from October 1987 through December 1989. Follow-up continued until December 1990 at the STD clinic of the Municipal Health Service of Amsterdam. Five hundred ninety-eight men and women entered the study. More than 70% of both women and men had had commercial sexual partners in the last 5 years. Three hundred eighty-one participants were born in HBV low endemic countries, 205 came from HBV intermediate endemicity regions. The prevalence of HBV markers in both men and women from low endemic regions was 10%, and for men and women from middle endemic regions 42% and 19%, respectively. Logistic regression analysis showed that number of years involved in commercial sex was an independent risk factor in male participants from HBV low endemic regions (odds ratio [OR] 1.10 per year) and for women sexual contact with men at high risk of HBV infection (OR 2.59).(ABSTRACT TRUNCATED AT 250 WORDS)

High mortality among HIV-infected injecting drug users without AIDS diagnosis: implications for HIV infection epidemic modellers?

OBJECTIVE: To quantify mortality without AIDS diagnosis (pre-AIDS death) among HIV-infected injecting drug users (IDU) and to compare it with that among homosexual men. SETTING: Municipal Health Service in Amsterdam, The Netherlands. DESIGN: HIV-infected participants of a cohort of homosexual men (recruited since 1984) and a cohort of IDU (recruited since 1985) were followed up to investigate the occurrence of AIDS and pre-AIDS death up to 1 October 1992. Both seroprevalent and seroconverted participants were included. METHODS: Product-limit estimates of cumulative AIDS incidence and cumulative pre-AIDS mortality were calculated for a competing risks model. RESULTS: Of 455 HIV-infected homosexual men, 127 developed AIDS and two died without a diagnosis of AIDS during follow-up; 31 out of 279 HIV-infected IDU were diagnosed with AIDS and 33 died without an AIDS diagnosis. After 6.5 years of follow-up an estimated 43.7% of the homosexual men had been diagnosed with AIDS and 0.7% had died without an AIDS diagnosis, while 32.7% of the IDU had been diagnosed with AIDS and 19.8% had died without an AIDS diagnosis. CONCLUSIONS: After 6.5 years of follow-up one-fifth of a group of HIV-infected IDU had died without being diagnosed with AIDS. This phenomenon seriously limits the number of HIV-infected IDU that may ever be diagnosed with AIDS and should be considered by HIV infection epidemic modellers. The new case definitions for AIDS will limit the number of recorded cases of pre-AIDS death.

Trends in sexual behaviour and the incidence of sexually transmitted diseases and HIV among drug-using prostitutes, Amsterdam 1986-1992.

OBJECTIVE: To determine trends in commercial sexual risk behaviour among drug-using prostitutes in Amsterdam after local and national prevention campaigns began in 1987. DESIGN: A subgroup of 281 drug-using prostitutes was selected from a comprehensive, open cohort study of drug users in Amsterdam. METHODS: Cross-sectional (at intake) and within-person trends in sexual behaviour were evaluated. Person-time analysis was used to determine trends in incidence of sexually transmitted disease (STD). RESULTS: From 1986 to 1992, 'always' use of condoms in the 6 months preceding intake increased from 21 to 58% (P < 0.001) and the number of commercial contacts declined from 84 to 64 per month (P = 0.06). Consequently, the mean number of unprotected commercial contacts declined from 26 to nine per month (P < 0.001). Temporal trends within individual prostitutes from visits 1 to 8 (mean interval between visits, 4 months) showed a somewhat larger risk reduction than the cross-sectional trends. From 1989 to 1992, the STD incidence declined from 61 to 40 episodes per 100 person-years (P = 0.06). Prostitutes residing in Amsterdam for shorter time periods reported more STD and a relatively small core group reported the majority of STD episodes. At intake, when < 10% of all participants knew their HIV serostatus, HIV-positive prostitutes reported significantly lower levels of condom use and more STD than HIV-negatives, while, after learning their serostatus, levels of condom use and the STD-incidence were comparable. Prevalent and incident HIV infections were not observed among non-injecting prostitutes. CONCLUSIONS: Drug-using prostitutes have reduced sexual risk behaviour. There is evidence for the effectiveness of HIV testing and counseling. At present, new infections among clients of drug-using prostitutes are expected to occur, although not on a large scale. Since the incidence of STD continues to be high, it is important to monitor the spread of HIV among heterosexuals, including prostitutes and their clients, closely.

Cervical HPV infection among HIV-infected prostitutes addicted to hard drugs.

An investigation into the prevalence of human papilloma virus (HPV) infection, abnormal cervical cytology and the relationship between HIV- and HPV infection was done in a group of intravenously (IV) and non-IV drug-using prostitutes. From July 1991 through May 1992, hard drug-addicted prostitutes attending a sexually-transmitted-disease (STD) clinic in Amsterdam were recruited. A questionnaire was administered to obtain demographic characteristics, and medical and STD history. Apart from routine STD examination, cervical scrapes for cytology and samples for HPV DNA detection by polymerase chain reaction (PCR) were collected. Some of the women included in this study also participated in HIV studies among drug users. Their data on HIV- and immunologic status could be combined. A total of 121 women entered the study; 25 women were HIV-seropositive, 44 women were HIV-negative, and the HIV status of 52 women was unknown. All 25 HIV-positive women had normal Pap smears, two of the 44 HIV-negative women had a Pap smear III A, and in the HIV-unknown group, two women with Pap III A and one with Pap III B were found. Eight of the 25 (32%) HIV-positive women were HPV DNA-positive, three of the 44 (7%) HIV-negative women and 10/52 (19%) of the HIV-unknown group. Logistic regression analysis showed that in the total group, presence or cervical HPV DNA was associated with HIV infection (order ratio [OR] for HIV-positives 7.8, 95% confidence interval [CI] 1.8 to 34.6) and with diagnosis of condylomata acuminata at entry to the study (OR 7.5, 95% CI 1.5 to 36.5).(ABSTRACT TRUNCATED AT 250 WORDS)

HIV prevalence and risk behaviour among prostitutes and clients in Amsterdam: migrants at increased risk for HIV infection.

OBJECTIVES: To study groups of prostitutes and clients of prostitutes in order (i) to determine HIV prevalence and sexual risk behaviour, (ii) to determine differences between samples recruited within and outside a clinic for sexually transmitted diseases (STD) and (iii) to determine correlates of inconsistent condom use (ICU) among both groups. DESIGN: Participants were interviewed and anonymously tested for HIV-antibody; approximately half were recruited at a clinic for sexually transmitted diseases (STD) and half at prostitute working places. SETTING: An STD clinic and prostitute working places in Amsterdam in 1991. SUBJECTS: 201 female prostitutes without a history of injecting drugs and 213 male clients of female prostitutes. MAIN OUTCOME MEASURES: antibodies to HIV, consistency of condom use in commercial vaginal contacts in the preceding 6 months. RESULTS: HIV prevalence was low: three prostitutes (1.5%; 95% CI 0.5-4.6%) and one client (0.5%; 95% CI 0.1-3.3%) were infected. All three HIV positive prostitutes originated from AIDS-endemic countries, came to the Netherlands only recently and were recruited outside the STD clinic. Large differences between subgroups resulted from the two recruitment methods: while clients of prostitutes with relatively high risk behaviour were strongly represented among the STD clinic sample, high risk prostitutes were underrepresented in this sample. Consistent condom use (with 100% of contacts) was reported by 66% of prostitutes and 56% of clients of prostitutes. Inconsistent condom use was found to be high among prostitutes who had migrated from Latin America and among migrant clients of prostitutes. CONCLUSIONS: When monitoring HIV infection one must take into account imported cases. HIV prevention efforts should be particularly focused at prostitutes from Latin America and at clients of prostitutes who migrated to the Netherlands.

[Prevalence of HIV in clients of an outpatient clinic for sexually transmissible diseases and in a group of prostitutes and their clients]. / HIV-prevalentie bij bezoekers van een polikliniek voor seksueel overdraagbare aandoeningen en bij een groep prostituées en prostituanten.

In order to gain insight into the heterosexual spread of HIV infections in Amsterdam, a study was carried out in 1991 among persons attending an outpatient clinic for sexually transmitted diseases (STD) and among a group of prostitutes and prostitutes' clients. Out of 2362 persons attending the STD clinic, 2138 (90.5%) could ultimately be examined for presence of HIV antibodies. The HIV seroprevalence was 4.2% (90/2138); among homosexual males it was 22% (70/324), among heterosexual male intravenous drug users 12% (2/17) and among heterosexual males who never had used i.v. drugs 0.5% (5/997). The HIV seroprevalence among female intravenous drug users was 41% (12/29) and that among females who never had used i.v. drugs it was 0.1% (1/771). Among the heterosexually active subjects (active in the preceding six months, including the groups of bisexual males and intravenous drug users), the seroprevalence amounted to 1.5% (28/1884). HIV antibodies could be demonstrated in 1.5% (3/199) of the prostitutes and in 0.5% (1/213) of prostitutes' clients. However, the one positive male had had homosexual contacts in the past. Out of the total of nine heterosexually infected persons, two originated from the Netherlands, two from Ghana, two from Turkey, one from Nigeria, one from Pakistan and one from the Dominican Republic; six of them had commercial contacts. The heterosexual spread of HIV among the heterosexual population of Amsterdam can for the moment be classified as slight. However, further heterosexual transmission of HIV cannot be excluded, considering the frequency of unprotected sex.

The harm reduction approach and risk factors for human immunodeficiency virus (HIV) seroconversion in injecting drug users, Amsterdam.

To assess risk factors for seroconversion to human immunodeficiency virus, the authors studied a cohort of human immunodeficiency virus-seronegative injecting drug users in Amsterdam, the Netherlands, between December 1985 and November 1991. The behaviors of 31 seroconverters were compared with those of 202 seronegative injecting drug users (controls). Three independent risk factors for seroconversion were found in logistic regression: 1) living greater than 10 years in Amsterdam (odds ratio (OR) = 2.45, 95% confidence interval (CI) 1.09-5.53); 2) first injection less than or equal to 2 years ago (OR = 3.43, 95% CI 1.20-9.81); and 3) injecting mainly at home (OR = 0.39, 95% CI 0.18-0.88). No evidence was found that receiving daily methadone treatments at methadone posts and obtaining new needles/syringes via the exchange program were protective. However, the data suggest that exchanging needles may have been protective at the start of this program. Influencing injecting drug users to modify behavior to prevent new infections appears to be very difficult, and it may, therefore, be important to increase preventive efforts targeted at the sexual partners of injecting drug users.

[Estimate of the number of HIV-infected intravenous drug users in Amsterdam]. / Schatting van het aantal met HIV geïnfecteerde injecterende druggebruikers in Amsterdam.

By combining data collected through a cohort study among injecting drug users (IDUs), which started December 1985, with data on the number of notified cases of AIDS, the cumulative number of HIV-infected IDUs residing in Amsterdam was estimated. The estimated cumulative incidence of HIV-infection among IDUs in Amsterdam on 1 July 1991 was about 1050. By 1 July 1991 90 of these cases had been diagnosed with AIDS, while an estimated 150-200 cases died before AIDS had been diagnosed. The prevalence of IDUs residing in Amsterdam who were still alive and free of AIDS on 1 July 1991 was estimated to be about 750-800. Because of untimely deaths, only a limited number of these HIV-infected IDUs can be expected to be diagnosed with AIDS in the future. The prevalence on 1 July 1991 of HIV-infected IDUs being alive and free of (diagnosed) AIDS and living elsewhere in the Netherlands is estimated at about 500.