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Objective: To gain insight into hepatitis B virus (HBV) transmission in the Netherlands., Design: Descriptive., Method: During 2004, epidemiological data and blood samples (if available) were collected for all reported cases of acute HBV infections in the Netherlands. Following DNA isolation and amplification a 648 base pairs fragment of the HBV S gene was sequenced and subjected to phylogenetic analysis. The sequencing details were also linked to epidemiological information., Results: In 2004, 291 cases ofacute HBV infections were reported. Blood samples were received from 171 patients (59%), and the genotype could be determined for 158 patients (54%). 6 genotypes were identified: A (64%), B (3%), C (3%), D (21%), E (5%) and F (4%). Of all patients with genotype A, 52% had been infected via homosexual or bisexual contact and 16% via heterosexual contact. Of all patients with genotype D, 42% had been infected via heterosexual contact and 15% via homosexual or bisexual contact. The genotype A cluster was extremely homogeneous with many identical sequences, while genotype B-E clusters were more heterogeneous. 4 identical sequences were found within genotype F, but the patients could not be epidemiologically linked., Conclusion: Sexual transmission, particularly via homosexual or bisexual contact in men, formed the most important risk factor for acquiring an acute HBV infection. Genotype A was predominant in the Netherlands, especially among homosexual or bisexual men. Most infections within genotype D occurred as a result of heterosexual contact. The results show that there was ongoing transmission of HBV in homosexual or bisexual men, while in heterosexuals more cases of new introduction were seen, possibly via chronic carriers from areas where HBV is endemic.

Objective: To investigate the epidemiological links between several outbreaks of hepatitis A in The Netherlands (2001-2004)., Design: Descriptive., Method: Blood samples taken in connection with reports of hepatitis A to municipal health centres from 2001-2004, were typed by determining the nucleotide sequence of the VP3-VP1 and the VP1-P2A regions of the genome of the hepatitis A virus (HAV). Genetic distances were represented graphically by means of a phylogenetic tree., Results: The study into the spread of various subtypes of HAV showed a clear link between the HAV-(sub)genotype and risk of transmission: in men that have sex with men only genotype 1A occurred, in travellers to African countries genotype 1B was predominantly seen., Conclusion: A database containing various viral strains from people with hepatitis A in The Netherlands could, if kept up to date, be used as an aid in confirming the classical way of tracing sources as well as for the evaluation of preventative measures.

During the period 6-28 July 2006, 30 confirmed cases of Legionella infection were identified in Amsterdam, 2 of which were fatal. All had a positive urinary antigen test, by which Legionella pneumophila serogroup I could be demonstrated. Consultations between the parties involved in the control of infectious diseases started on July 7th, as soon as it became clear that there was an outbreak. On July 10th it was established that relatively many of these patients lived in the eastern part of the city centre. After a study of the prevailing winds during the past 3 weeks, the search for installations containing water was started. A cooling tower in the town centre was closed on July 11th by way of precaution. During the following week, this tower was proven to be the source of the outbreak.

In 2003 the Municipal Health Service in Amsterdam started to screen pregnant women for HIV according to the opting-out method. In this method the HIV test is routinely included in the prenatal screening along with hepatitis B virus (HBV) and syphilis. If the woman does not want to be tested for HIV then she must actively opt out of this test. This screening method was chosen because in the universal screening method used in 2002, women had to give their explicit consent to test for HIV and this led to a high refusal rate (13.6%), especially among women from AIDS-endemic countries. After the introduction of the opting-out method, the refusal rate fell from 3% in the first quarter of 2003 to 1.4% in the last quarter of 2003. None of the women refused to be tested for HBV or syphilis. In 2003, the HIV prevalence among pregnant women was 0.3% (35/13.621). The experiences with this screening method in Amsterdam were used to implement the national opting-out method for HIV screening in pregnant women, which was introduced on 1 January 2004.

A study of the registered number of Shigella infections in Amsterdam for the period 1997-2001 revealed that in 2001, there was an increase in the number of homosexual patients with oral-anal contacts as source for their infections. All of these infections were caused by subtype Shigella sonnei. The infections were not associated with a specific meeting place for homosexual men. A relationship with an underlying HIV-infection is likely.

In 2001, the Municipal Health Service started offering HIV tests to all pregnant women in and around Amsterdam. All midwives and all hospitals but one participated in this HIV screening. In 2002, of the 10,752 pregnant women offered HIV testing 13.6% refused. HIV antibodies were detected in 24 women (0.26%). The HIV prevalence was doubled compared to the prevalence in 1990-1991, but the number of newly HIV-infected pregnant women remained stable (0.1%). The high number of refusals, as a result of which many HIV-infected women might be missed, is alarming. For this reason, in January 2003, the Municipal Health Service started HIV testing by the opting-out approach. Under the opting-out approach, women are notified that an HIV test will be included in the standard test battery, together with tests for hepatitis B and syphilis, unless she explicitly refuses. It is expected that the opting-out approach for HIV screening of pregnant women will be implemented nationwide in 2003.

Objective: To determine the travel behaviour of inhabitants of Amsterdam, the Netherlands, with respect to age and ethnicity, as well as the impact of travel advice, in particular regarding hepatitis A vaccination of Turkish and Moroccan children., Design: Descriptive., Method: In a sample of 2000 inhabitants of Amsterdam, a survey was carried out during the period October 1999-November 2000 on seeking medical advice prior to travelling. In addition, 429 Turkish and Moroccan parents were questioned about hepatitis A vaccination of their children when travelling to their country of origin., Results: In the three years preceding the survey one third of the Amsterdam population travelled to a country where infectious diseases such as malaria and hepatitis A were endemic. Many travellers (18%) went to Asia, Central or Latin America and Africa. Others (12%) travelled to the Middle-East or North Africa. One third of the travellers had sought advice from the Municipal Public Health Service of Amsterdam. Other travellers were advised by their general practitioner (10%). A large group (38%) did not seek any advice at all. Almost one third of the travellers went to their country of origin, particularly Turkish and Moroccan inhabitants of Amsterdam. Seventy percent of Turkish and Moroccan travellers had not sought travel advice. More than half the Turkish and Moroccan parents did not have their children vaccinated against hepatitis A when travelling to their country of origin., Conclusion: One fifth of the indigenous Dutch population received no travel advice. More than half of Turkish and Moroccan children travelling to their country of origin were not vaccinated against hepatitis A.

Objective: To determine the incidence of patients reported with typhoid fever in Amsterdam (1991-2000) and to evaluate the contact tracing for those patients with the specific objective of examining whether contact tracing can be simplified., Design: Retrospective., Method: From an automated database, data were collected on all reported typhoid fever patients in Amsterdam during the period 1991-2000 and on their contact persons., Results: One hundred and one patients with typhoid fever were reported during the study period, and Salmonella typhi infection was diagnosed in 12 of the 281 household contacts. For 96 of the 101 index patients, travelling abroad was the most likely source of infection. In 8 of the 12 contact persons with an S. typhi infection, the index person was the most likely source of infection, which is equivalent to a secondary transmission rate of 2.8% (8/277). Seven of the 8 secondary infected persons had symptoms indicative of typhoid fever infection and S. typhi was found in all their first stool samples., Conclusion: Supported by these results, the national guidelines for source and contact tracing in the case of typhoid fever have been amended. In the case of index patients with bad toilet hygiene or who are responsible for food preparation, the faeces of all household contacts must be examined once. If the contact persons have symptoms indicative of an S. typhi infection and/or if their work involves food preparation, their faeces should also be tested once. The changes to the national protocol will markedly reduce the labour-intensity of tracing and testing the contacts of patients with typhoid fever, thereby maintaining the quality of the process. Tracing the source of infection in the case of patients with typhoid fever will also remain important in the future in order to detect potential transmission within the Netherlands at an early stage.

The Infectious Diseases Department of the Amsterdam Public Health Service regularly sees people who have possibly been exposed to human body fluids infected with hepatitis B virus (HBV), hepatitis C virus (HCV) or human immunodeficiency virus (HIV), as a result of incidents in either a non-hospital-related occupation or during their leisure time. Until January 2000, people reporting possible exposure were referred to hospitals for HIV post-exposure prophylaxis (HIV-PEP), whereas for HBV and HCV, the tracing of the infection source and the follow-up took place at the Public Health Service clinic. Since the introduction of a new protocol in January 2000, the Public Health Service as well as a hospital can establish an indication for HIV-PEP and prescribe it. In 2000, 322 persons reported to the Public Health Service. The source was tested in 194 incidents and an HIV test was carried out on 104 occasions. In 19 cases HIV antibodies were found or the source was known to be HIV positive. A total of 50 people were prescribed HIV-PEP; 16 times after a needle-stick accident, 22 times after a sexual accident, 6 times after a bite-wound and 6 times after direct exposure to human blood. The sources of 30 PEP recipients could be tested and after this 16 recipients could stop with the treatment due to a negative HIV test. In 4 cases PEP treatment was stopped following a review of the indication. Therefore, 30 people had an indication to complete the PEP treatment. Of these, more than 80% reported side effects and 3 people had to withdraw from the treatment at an early stage because of this. The implementation of the protocol has resulted in less confusion because the follow-up now takes place at one location. Compared to other studies, the average time between exposure and treatment is shorter and compliance is good. In the period up to 15 May 2001, no seroconversions had been observed.

Long-term exposure to organic solvents can result in damage of the central nervous system. The WHO recognises the following stages: organic affective syndrome, mild chronic toxic encephalopathy (CTE), and severe CTE. There is no golden standard for the diagnosis of CTE. Mild CTE is characterised by fatigue, mood disturbances, memory and attention disorders. In the Netherlands, a so-called 'solvent team' consisting of an occupational physician, a neurologist, a neuropsychologist and an occupational hygienist, assesses patients suspected of having CTE. The diagnostic procedure consists of three steps: (a) interview and blood tests, (b) the computer-based Neurobehavioral Evaluation System, and (c) assessment of an exposure index, neuropsychological investigation, and clinical neurological examination. In the period 1997-1999 approximately 250 patients were assessed yearly in the Netherlands; resulting in 50 diagnoses of mild CTE a year. The real incidence is most likely higher at present, but will decline due to diminished exposure to organic solvents.

Objective: To estimate the cost-effectiveness of antenatal screening for Chlamydia trachomatis., Design: Pharmaco-economic model analysis., Method: The risks of C. trachomatis infection during pregnancy and of complications of the infection as well as the cost of screening for complications (pelvic inflammatory disease, chronic pelvic pain, ectopic pregnancy, infertility and neonatal pneumonia) and of treatment were estimated. Assumed were a ligase chain reaction on urine and treatment of identified infected cases with erythromycin or amoxicillin (second choice). Cost-effectiveness was calculated and presented in net direct and indirect costs per major complication averted., Results: For C. trachomatis prevalences in pregnancy above 4% benefits exceed the costs. For prevalences between 2.82% and 4.00% net costs are positive, but a major complication averted costs less than f 1000.-. Considering sensitivity analysis as well, screening for C. trachomatis at prevalences above 3% costs less than f 1000.-per major complication averted and might even save costs. No recent Dutch data on C. trachomatis prevalence in pregnancy are published however., Conclusion: Given the current information, antenatal C. trachomatis screening can be recommended from a pharmaco-economic perspective if C. trachomatis prevalence in pregnancy is 3% or more.

Objective: To determine the incidence of reported shigellosis in Amsterdam (1991-1998) and the factors related to the secondary attack rate of shigellosis., Design: Retrospective., Methods: From an automated data bank data were collected on all registered shigellosis patients in Amsterdam in the period 1991-1998, and their contacts found by contact tracing., Results: 567 Patients with shigellosis had been reported and a Shigella infection has been diagnosed in 96 of the 983 contacts. The annual incidence decreased statistically significantly from 13 to 8/100.000. 329 males and 334 females were infected. The highest number of cases was found in children from 0-4 years and among adults from 20-34 years. Of the 663 patients 106 (16%) required hospitalization; for children under 7 this proportion was 30% (32/108). Among the contacts (excluding the 14 contacts with the same foreign source and the same first sickness day as the index patient) the secondary attack rate was 8%. Young age, of both the patient and the contact was independently related to a higher secondary attack rate., Conclusion: With contact tracing for shigellosis a large number of secondary infections were found. Given the high infection rate and large number of hospitalisations among children, contact tracing should focus at this young age group.

Objective: To estimate the cost effectiveness of universal screening for HIV of pregnant women in Amsterdam., Design: Pharmaco-economic model calculation., Method: An estimate was made of the minimal and maximal prevalences of undiagnosed HIV infection during pregnancy for the whole of Amsterdam, based on epidemiological data from observation among pregnant women in two Amsterdam hospitals and one obstetrical practice. The calculation was based on universal screening with an ELISA test. The interventions after screening comprised pharmacotherapy during pregnancy, delivery by caesarean section and breast-milk substitution. The issues of pharmaco-economic analysis were whether or not costs were reduced and net costs per year of life gained; the question was also studied at what lifetime costs of care for HIV infected children the net costs would be nil (costs equal benefits)., Results: Universal HIV screening in Amsterdam required a total investment of about Dfl 300,000.-per annum. In many of the analysed options for HIV screening the financial profits exceeded the investment. Variation of assumptions showed that the net costs of HIV screening under all conditions investigated would remain below Dfl 1,200.-per life year gained., Conclusion: Universal HIV screening of pregnant women in Amsterdam showed a favourable cost effectiveness. The calculations indicated a possibility of reducing costs.

The role of reinfection and the importance of partner treatment were added to a pharmacoeconomic model for the analysis of a GP-based opportunistic screening programme for Chlamydia trachomatis (CT) in sexually active women in Amsterdam. A favourable cost-effectiveness was found for partner treatment. Partner treatment was cost saving and overall net costs per major outcome averted by the screening programme were reduced by 40% or more due to partner treatment. From a pharmacoeconomic point of view partner treatment should be routinely provided in the framework of a CT screening programme for Amsterdam women.

Objective: To determine in an opportunistic screening programme for Chlamydia trachomatis (CT) the participation and the CT prevalence among the heterosexual population., Methods: Heterosexually active men and women, 15-40 years old, who consulted a general practitioner in Amsterdam, the Netherlands, in the period May 1996-April 1997, without symptoms of a sexually transmitted disease, were asked after informed consent had been given to provide a first-voided urine sample and a few sociodemographic data. The urine was investigated for CT by means of a ligase chain reaction. In case of a CT infection, the general practitioner was asked for information on treatment and partner notification., Results: A total of 3689 persons were eligible for the study of whom 214 (5.8%) refused participation. Men refused more often than women (9.0% and 4.3% respectively). No relation was found with ethnic background or health care insurance (national health cost insurance/private medical insurance). Refusers were somewhat younger than participants (not statistically significant). CT was diagnosed in 4.9% (95% confidence interval (95% CI): 4.1-5.9) of the women and in 4.7% (95% CI: 3.6-6.1) of the men. In women a decreasing trend was seen in the prevalence of CT with an increase in age: from 13.4% in the group 15-19 years old to 2.3% in the group 35-40 years old. Independent of age a higher prevalence was found in Surinam Creole women. In 83% of the CT patients the general practitioner spoke with the patient about partner notification; usually there was one partner., Conclusion: There was a high participation rate (94%) in this opportunistic screening programme in which urine was tested for presence of CT. The CT prevalence in this asymptomatic population was almost 5%, but it was significantly higher in young women and women from Surinam. It is proposed to start such a screening programme in all general practices in Amsterdam.

Objective: To estimate the cost effectiveness of Chlamydia trachomatis (CT) screening of young women visiting general practitioners., Design: Economic model analysis., Methods: Data on the health care needs for CT complications were derived from various sources; costing was done using estimated cost prices, charges and the friction cost method; epidemiological data were derived from a pilot study among 22 general practices in Amsterdam, the Netherlands. The analyses were carried out assuming screening with ligase chain reaction test of a urine sample and treatment of identified cases of infection with single-dose azitromycin. The model intervention consisted of screening all heterosexually active women aged 15-19, 15-24, 15-29, or 15-34 years (strategies 1, 2, 3 and 4, respectively). Cost effectiveness was presented in net direct and indirect costs per woman cured and per major outcome averted (pelvic inflammatory disease (PID), chronic pelvic pain, ectopic pregnancy, infertility and pneumonia of newborns)., Results: The first two strategies were cost saving. For the third strategy net costs per woman cured and per major outcome averted were almost 110.- Dutch guilders (DFL) and over DFL 300, respectively. The last strategy costs over DFL 320 per woman cured and over DFL 910 per major outcome averted. The cost effectiveness was sensitive to the assumed probability of progression of CT infection to PID., Conclusion: Universal implementation of the screening programme investigated in Amsterdam for women aged 15-24 years would result in approximately equal savings and costs. Screening of all 15-29-year-old women would require a net investment of DFL 350,000.

Data were collected in Amsterdam in 1997 from the aids surveillance, from the HIV surveillance among pregnant women and visitors of a clinic for sexually transmitted diseases (STD), and from two 'alternative' HIV test sites, using various survey systems. The findings were compared with those of previous years. Aids was diagnosed in 1997 in 123 patients, in 194 in 1996. Of the 354 patients in whom aids was diagnosed in 1993-1997 in a hospital recording additional information, 113 patients (32%) only learned that they had an HIV infection when aids was diagnosed in them. In 1997, out of 225 pregnant women with an increased risk of HIV infection, 10 were HIV seropositive (4.4%); in 1996, this proportion was 3/285 (1.1%). Among those attending STD clinics, HIV infection was observed approximately as frequently as in earlier years: about 1% of heterosexual men and women.

Objective: To determine the prevalence of HIV infection and risk behaviour among various groups of streetwalkers in Amsterdam and the extent of overlap between different prostitution networks., Setting: The family room project in the streetwalkers' district in Amsterdam, the Netherlands., Methods: In November 1996, saliva was taken from 32 female and 25 transsexual/transvestite prostitutes and tested for antibodies against HIV. Besides, prostitutes were interviewed on risk behaviour, history of sexually transmitted diseases and mobility., Results: Only one of the participants (a female prostitute) had ever injected drugs. None of the female prostitutes, but 6 of the 25 transsexuals/transvestite prostitutes (24%; 95% confidence interval: 7-41) proved seropositive. None of the HIV infected participants was aware of his serostatus. The transsexual/transvestite prostitutes frequently had receptive anal intercourse with their clients. Condom use was high, but most did not use condoms made for anal intercourse. Female prostitutes also reported a high rate of condom use with their clients. Both groups of prostitutes reported few private partners and a low rate of condom use with these partners. According to the transsexual/transvestite prostitutes many of their clients had sexual contacts with women in their private lives. Many prostitutes thought that they shared the same clients in the district., Conclusion: HIV infections occur quite often among transsexual/transvestite prostitutes in the streetwalkers' district in Amsterdam. The risk of further spread HIV infection to their clients (and through them to other heterosexual populations) is present. AIDS education targeted at this group is important. The use of (special) condoms when having anal intercourse in private as well as in prostitution contacts should be emphatically advised.

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.

Since 1984/1985 a cohort of homosexual men (HM; n = 770 initially HIV-seronegative) and one of injecting drug abusers (IDU; n = 675 initially seronegative) are being followed in Amsterdam, in order to assess the HIV epidemic in these high-risk groups. The HIV incidence in HM fell from 7.2/100 person years in 1985 to 1.0 in 1989, due to safer sexual behaviour. In 1990 there was a temporary rise in HIV incidence coinciding with an increase in gonorrhoea and syphilis in homosexual/bisexual men (not in the cohorts) attending a sexually transmitted diseases outpatient clinic. The rise was due to a relapse in unsafe sexual behaviour. After 1990 the HIV incidence dropped again and it remained at 1/100 person years in 1995. In IDU, in whom a reduction was found in both injecting and sexual risk behaviour, the incidence fell from 8.9 in 1986 to 2.0-3.6/100 person years in 1991-1995. In order to follow the future course of the HIV epidemic, it is argued to open the cohorts particularly for young HM and IDU.

Objective: To assess the HIV prevalence among heterosexual attenders of a clinic for sexually transmitted diseases (STD) and among subpopulations, including young gay men and ethnic minorities., Setting: Outpatient clinic for sexually transmitted diseases (STD) of the Municipal Health Service of Amsterdam, the Netherlands., Methods: Semi-annually in the period 1991-1994, blood samples given voluntarily and anonymously were tested for HIV antibodies and some characteristics were collected of approximately 1000 clinic attenders., Results: Since 1991, 6766 clinic attenders were eligible for participation, of whom 6200 (92%) were actually tested. The overall HIV prevalence decreased from 3.9% in the first half of 1991 to 2.3% in the second half of 1994. Among heterosexual clinic attenders the prevalence remained stable below 1%, due mainly to visitors from abroad rather than to Dutch heterosexuals: 20 of the 23 HIV infected heterosexuals were not Dutch. None of these 23 seropositive persons knew of their HIV infection, mostly because they had not been tested previously. The HIV prevalence among gay men decreased over the years. In addition, the number of gay male attenders younger than 30 years decreased strongly over time., Conclusions: HIV infections among heterosexual STD clinic attenders are relatively few and are seen mainly among non-Dutch. We found no indications of an increase of the HIV prevalence among heterosexual clinic attenders. The results among young gay men are suggestive of a shift towards safer sexual behaviour in this group.

Objective: To evaluate the survival of 975 AIDS patients diagnosed in the Amsterdam region between 1982 and 1991, with follow-up until December 31st, 1992., Methods: Analysis of data from the active AIDS surveillance system for the Amsterdam region at the Municipal Health Service., Results: Amsterdam region residents had 1, 2 and 3-year survivals of 69.8%, 42.6% and 21.2%, respectively. The 5-year survival was 7.7%. The median survival probability for all patients showed great improvement, from 9 months in 1982-1985 to 26 months in 1990. For patients initially presenting with only Pneumocystis carinii pneumonia (PCP) the greatest improvement occurred between the period 1982-1985 and the year 1986. For patients without PCP the most important improvement occurred one year later. From 1988 onwards no important improvement in the 1-year survival is noticed. The 2-year survival, however, appears still to be increasing. In a Cox proportional hazards model the following variables were found to be independent predictors for survival: age at diagnosis, earliest clinical AIDS manifestations, year of diagnosis and HIV risk group. No differences were seen in the 1 and 2-year survival probabilities for men and women with AIDS. Heterosexual men and women tended to have a poorer survival than intravenous drug users and homosexual and bisexual men., Conclusion: A noticeable improvement in the survival probability with time occurred for AIDS patients living in the Amsterdam region through the years 1982-1991, although the overall survival after AIDS diagnosis is still poor. The 1-year survival appears to have reached a plateau, the 2-year survival is still increasing. Improved clinical experience, awareness of HIV related complaints in high risk groups, better diagnostic methods and the availability of proper medication (prophylactic and treatment) are the most likely explanations of the improvement in survival.

Objective: To determine the prevalence of sexual behaviour with the risk of HIV transmission among young homosexual men in Amsterdam., Design: Point prevalence study., Setting: Amsterdam., Methods: Participants were recruited through advertisements and in gay bars and a STD clinic in the period October 1991-1992. A questionnaire regarding sexual behaviour was completed, and blood samples were drawn to test for presence of serological markers of HIV infection, hepatitis B and syphilis., Results: Enrolled in the study were 154 men (mean age: 25 years). The prevalence of antibodies against HIV was 5% and that of hepatitis B 22%. Receptive anogenital intercourse with steady partners in the previous six months was reported by 60% (74% sometimes without a condom), with non-steady partners by 41% (40% without a condom). The figures for insertive anogenital intercourse were: steady partners: 45% (74%); non-steady partners: 49% (41%). Overall 43% (66/153) reported at least one unprotected anogenital contact in the previous six months. The presence of HIV antibodies was correlated with the number of partners with whom anogenital sexual intercourse was practised., Conclusion: The HIV prevalence (5%) was relatively low. Considering the high prevalence of unsafe sexual behaviour further spread of HIV infection among young homosexual men is to be expected.

Objective: To determine the HIV prevalence and the frequency of injecting drugs among drug users from Surinam and the Netherlands Antilles in Amsterdam., Design: Descriptive study., Setting: Amsterdam streets., Method: Participants were recruited in 1992 in the street and interviewed about their drug use behaviour, sexual life style and previous HIV test results. Blood or saliva samples were collected for HIV antibody testing., Results: Of 198 participants recruited, 185 (93%) were males. The mean age was 38 years. The mean duration of stay in the Netherlands was 19 years and mean duration of drug use 14 years. Sixty-eight percent of the participants received methadone treatment. Injecting drugs at any time was reported by 29 (15%) participants. Injecting drug users (IDU) more often had a steady partner who also injected or otherwise used drugs. Nearly one-quarter reported having had sex with a steady or casual IDU partner. HIV prevalence among IDU was 17% (5/29; 95%-CI 7.4-35%), among heterosexual male non-IDU 4.5% (7/156; 95%-CI 2.1-9.1%) and among female non-IDU 9.1% (1/11; 95%-CI 1.3-44%). HIV positive heterosexual non-IDU reported a higher mean number of heterosexual partners in the past 6 months (7.1 versus 1.3), more often had had hepatitis and more often were blood transfusion recipients than HIV negative heterosexual non-IDU., Conclusion: HIV prevalence among IDU in this study did not differ from the prevalences found among other IDU in Amsterdam. However, HIV prevalence among heterosexual non-IDU originating from Surinam and the Netherlands Antilles was high when compared with other non-IDU heterosexuals in Amsterdam and may indicate the presence of heterosexual transmission of HIV. Underreporting of risk behaviour or transmission through blood transfusion however, cannot be excluded completely.

Ten years after the start of the AIDS epidemic in the Netherlands the proportion of persons infected by heterosexual contacts among the total of AIDS cases diagnosed is small (7.4%). Up to December 1991 the cumulative totals of females and males in the Netherlands reported with the diagnosis and infected by heterosexual contact were 55 and 93, respectively. Of the 55 heterosexual females, 69% had the Dutch nationality, of the 93 heterosexual males, 67%. Considerable proportions of the numbers of AIDS patients in this group (males 47%, females 45%) were diagnosed in the four largest cities (Amsterdam, Rotterdam, The Hague and Utrecht). The remaining cases of AIDS diagnosed in this group were scattered throughout the country. Among heterosexual females a gradual increase of the number of AIDS cases diagnosed was observed since 1985. In the males there was no clear trend in the number of diagnoses since 1984. Of the 55 females, 19 originated from an area endemic for AIDS or had had sexual contacts with a person from such a region (34.6%). Among the 93 males this number was 29 (31.2%). Nineteen of the 55 females (34.6%) were known to have sexual contact with a person from the known risk groups. The same held true of 12 males (12.9%). Of the remaining 17 females (30.9%) and 52 males (55.9%) it was only known that they were heterosexual without further risk factors or risk contacts.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

The results of the serological syphilis screening programme for pregnant women in the region of Amsterdam in the period 1985-1989 are described. In addition, a cost-benefit analysis was done to determine useful effects of the programme. Every GP and obstetrician routinely takes blood samples from pregnant women to determine the blood group, rhesus factor and syphilis serology. In the period 1985-1989, a total of 37,520 serum samples were screened for syphilis in the Amsterdam region by the Central Laboratory of the Blood Transfusion Service (until mid-1986) and by the Regional Public Health Laboratory of the Municipal Health Service (from mid-1986). In 55 women (0.15%) both the Treponema pallidum haemagglutination assay (TPHA) and the venereal disease research laboratory (VDRL) tests were positive. Further evaluation of these 55 women ultimately brought to light 10 women with positive syphilis serology who had not been treated and consequently might infect their child with Treponema pallidum. Considering the various transmission percentages of the bacterium from mother to foetus, which depend on the stage of the maternal infection, the screening programme has prevented two cases of congenital syphilis. This brings the cost-benefit ratio of the syphilis screening programme for the region of Amsterdam to 1:6.2. In view of these findings there is no reason to reconsider the current screening practice in Amsterdam.

Between September 1987 and January 1989 101 drug users in The Hague were studied for HIV seroprevalence and risky injecting behaviour. A comparison was made between this group and a group of 241 drug users who were studied in the same period in Amsterdam. All HIV-infected drug users, except for one homosexual man in Amsterdam, had a history of intravenous drug use. The HIV seroprevalence for 56 intravenous drug users in The Hague was 1.8% (95% CI: 0-5.3), and for 194 intravenous drug users in Amsterdam 26.8% (95% CI: 20.6-33.0). With regard to risky injecting behaviour no differences in frequency of borrowing or lending used needles and syringes were found between the two groups. Concluded is that further spread of HIV among intravenous drug users in The Hague (and Amsterdam) will be likely unless risk reduction in injecting behaviour will occur.

Since 1981, the notified incidence of gonorrhoea has been decreasing in The Netherlands, thus preceding the onset of the AIDS epidemic. The declining trend of gonorrhoea and its underlying reasons are investigated. The reporting patterns may be influenced not only by the disease incidence but by other factors as well. Therefore the national notification gonorrhoea data over the period 1976-1988 are analysed in conjunction with detailed data from the two sexually transmitted diseases (STD) clinics in Amsterdam. Since 1983 the decline in gonorrhoea has been further reinforced by a dramatic decrease in gonorrhoea among homo/bisexual men, presumably as a result of behavioural changes because of AIDS. There is less evidence of massive behavioural changes among heterosexuals. The incidence of repeat infection among the gonorrhoea population in Amsterdam increases and may suggest that sexually highly active individuals continue to put themselves at risk of STDs, despite the educational campaigns with respect to the AIDS epidemic.

We studied the prevalence of Chlamydia trachomatis (CT) infection as well as its predictors among a sample (1000) of visitors (651 male, 349 female) of a clinic for sexually transmitted diseases (STD) in Amsterdam. The prevalence of CT was higher than that of gonorrhoea: among men, 14.3% and 11.5% and among women, 12.9% and 6.3% respectively. Independent predictors for CT infections were for men: number of leucocytes in discharge or urine, nature of urethral discharge, age and sex behavior, and in women: being warned as source or contact of a STD, age, nature of cervical discharge and bleeding from the cervical ostium after insertion of a swab. As many as 92% of the male and 81% of the female visitors of our STD clinic should be examined for CT if the presence of anyone or more of these predictors is taken as a criterion. Even then, 5% of the CT infections in women would still be missed. Based on our study results, material for the diagnosis of CT will from now on be collected routinely from all female patients of our STD clinic as well as from all males with urethritis. We advocate the expansion in the Netherlands of facilities for laboratory CT detection and its standard inclusion in STD examination.

Since 1981 sexually transmitted diseases (STD) diagnosed at the STD clinics of the Municipal Health Service of Amsterdam, are registered by sex, sexual orientation and prostitution. Numbers of diagnoses per 1,000 new consultations are compared for each group of visitors over the period 1981-1987. Among heterosexual visitors there has been a steady decline of gonorrhoea and trichomoniasis since 1981. Genital herpes and venereal warts after increasing until 1985 have reached a plateau. Because of the early appearance of these trends they cannot be attributed to changes in heterosexual behaviour brought about by the AIDS epidemic. Nongonococcal urethritis has been increasing since 1981, possibly due to insufficient Chlamydia trachomatis detection in the country. After several years of decline, early syphilis has been increasing since 1987 among heterosexual men and women. Among homo/bisexual men the numbers of cases of gonorrhoea and early syphilis as well as the number of consultations for STD have decreased strongly since 1984, which may well be the result of changes in homosexual behaviour because of AIDS.