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Objectives: To adapt and improve methodology for back-calculation of AIDS in Europe and to examine the feasibility of estimating past HIV incidence by birth cohort., Methods: Empirical Bayesian back-calculation (EBBC) used Markov disease progression models, modified to allow for three diseases added to the AIDS case definition in 1993 and for pre-AIDS mortality, and estimation by penalized maximum likelihood with a neighbour prior. EBBC by 5-year birth cohort assumed a minimum age at infection and age-dependent progression rates; three versions, with varying age effects, were investigated using AIDS cases diagnosed prior to the introduction of highly active antiretroviral therapies (HAART)., Results: Compared with the no age-effect version, EBBC by birth cohort tended to produce flattened HIV incidence curves in country-exposure groups with < 1000 AIDS cases, reflecting effects of the neighbour prior when data become sparse. Otherwise, birth cohort analysis, with moderate effects of age on progression, gave initially increasing incidence curves and consistent patterns across countries, with the 1960-1964 cohort most affected. In the European Union, incidence is estimated to have peaked in 1983 among homosexual men and in 1988 among injecting drug users; 460000 persons were estimated to be living with HIV/AIDS at the end of 1995., Conclusions: Our improved methodology deals effectively with the change in AIDS case definition and has allowed quantitative assessments of the HIV epidemic by birth cohort using all AIDS cases diagnosed before 1996, thus providing a sound basis for public health policy at a time when estimation of more recent prevalence is compromised by the effects of HAART.

Objective: To estimate the cost effectiveness of universal, voluntary HIV screening of pregnant women in England., Design: Cost effectiveness analysis. Cost estimates of caring for HIV positive children were based on the stage of HIV infection and calculated using data obtained from a London hospital between 1986 and 1996. These were combined with estimates of the health benefits and costs of antenatal screening so that the cost effectiveness of universal, voluntary antenatal screening for HIV infection in England could be estimated., Main Outcome Measures: Lifetime, direct costs of medical care of childhood HIV infection; life years gained as a result of the screening programme; net cost per life year gained for different pretest counselling costs; and different prevalence rates of pregnant women who were unaware that they were HIV positive., Results: Estimated direct lifetime medical and social care costs of childhood HIV infection were pound178 300 using a 5% discount rate for time preference (1995-6 prices). In high prevalence areas screening pregnant women for HIV is estimated to be a cost effective intervention with a net cost of less than pound4000 for each life year gained. For areas with comparatively low prevalence rates, cost effectiveness could be less than pound20 000 per life year gained, depending on the number of pregnant women who are unaware that they are infected and local screening costs., Conclusions: Our results confirm recent recommendations that universal, voluntary antenatal HIV screening should be implemented in the London area. Serious consideration of the policy should be given for other areas in England depending on local prevalence and screening costs.

HIV surveillance in homosexual men is poor in most countries, as this risk group is difficult to sample. The aim of this study is to test the feasibility of reaching homosexual men for national HIV surveillance using gay community media. In 1989, a questionnaire on general gay issues, with a section on AIDS, was included in a widely sold gay magazine in the Netherlands. Among 17,700 sold copies, 1134 responses were obtained from males (6%). Of these, 669 men (59%) gave their address, of which in turn 84% responded to a questionnaire on risk behaviour in 1990. In 1991/1992, the 669 men were asked to participate in an HIV serosurvey, in which eventually 308 participated with a blood test (46%) and 147 without (total 68%). Participation in the serosurvey with blood test was associated with reporting multiple partners in 1989. Twenty participants were infected (6.5%). In logistic regression analysis, risk factors for infection were recent unprotected receptive anal intercourse with multiple partners (odds ratio (OR): 10.7; 95% confidence interval (CI): (2.18-52.2); one partner 1.17 (0.31-4.48); none 1) and living in Amsterdam (OR: 3.92; 95% CI: (0.99-15.5); urbanised western Netherlands 2.15 (0.57-8.03); elsewhere 1), while a high educational level was protective (OR: 0.29 (0.08-0.96); middle 0.41 (0.11-1.54); low 1). Among those who participated in 1991/1992, risk behaviour increased between 1989 and 1991/1992 (reporting multiple casual partners rose from 55% to 64%; reporting inconsistent condom use with receptive anal sex from 58% to 71%). Using a predictive model which included self-reported serostatus in 1989, the HIV prevalence rate in 1991/1992 among all male responders to the 1989 questionnaire was estimated to be 5.3% (95% CI: 3.1 7.7%). In conclusion, unless initial response is improved, recruitment through a gay magazine may not allow reliable estimates of HIV prevalence in homosexual men. However, it can be useful at the national level for monitoring changes in prevalence and risk behaviour over time, geographical differences and risk factors for infection.

In this study on occupational risks of HIV infection among 99 Dutch medics working in AIDS endemic areas, 61% reported percutaneous exposures during an average stay of 21 months. The mean number of injuries was lower among physicians (2.0 versus 3.9 per year) and higher among nurses (1.9 versus 1.2) than in previous research conducted in 1987-1990 among Dutch medics returning from Africa. But the reduction of exposures among physicians might be explained by the fact that the number of procedures they carried out was less in the later study. Also among nurses a shift of tasks was seen. On the basis of an estimated HIV prevalence in the patient population of 19%, a chance of transmission per accident of 0.3%, and 1.9 percutaneous exposures per year, the mean occupational risk of HIV infection per year can be estimated at 0.11% per person. Besides length of stay and number of activities, characteristics of the work setting were associated with the frequency of different kinds of injuries. From the analysis of 109 extensive descriptions of recent accidents, it appeared that the majority of the injuries occurred during routine activities and were self-inflicted. Injuries with hollow needles usually occurred after the actual medical act (e.g. during recapping). Carelessness (e.g. due to fatigue) or being in a hurry (e.g. because of an emergency) were also often the cause of percutaneous injuries, as were the poor quality of the equipment, lack of professional skills, or a combination of these factors. Prevention activities are still important to reduce the frequency of occupational exposures. But they will not eliminate them totally; from the descriptions of recent exposures it was clear that some of the injuries occurred in spite of precautions.

An abrupt decrease of the number of reported new AIDS cases took place in the first half of 1997 in the Netherlands. This decrease was most prominent in homosexual/bisexual men and intravenous drug users, and less conspicuous in heterosexual men and women. The number of heterosexual patients with a non-Dutch nationality even increased compared with the first half of 1996. The most probable explanation of these observations is the introduction of improved treatment possibilities for HIV-infected people starting July 1996, which lead to a longer incubation period. Owing to these developments monitoring the HIV/AIDS epidemic in the Netherlands will depend more and more on HIV status surveillance instead of on registration of new AIDS cases.

Objective: To assess the prevalence of HIV infection and related risk factors among Dutch expatriates returning from assignment in sub-Saharan Africa, Latin America, and South and South-east Asia., Methods: From July 1994 to January 1996, a questionnaire on the risks of sexual exposure was completed by 864 respondents, and blood samples were taken., Results: Of the 634 men, 41% reported having sex with casual or steady local partners and 11% with casual or steady expatriate partners, during an average stay of 26 months in the previous 3 years. Of the 230 women, these figures were 31 and 24%, respectively. Of the men with local casual partners (29%), 59% paid for sex at least once. For men as well as women, having sexual contacts abroad was associated with younger age, positive intention prior to departure to have sex abroad, being single at departure, and, only for the men, working for a commercial organization, and feelings of loneliness and boredom. Among men, consistent condom use with casual local partners was 69%, and with casual expatriate partners 63%. Among women, these figures were 64 and 48%, respectively. Consistent condom use with steady local or expatriate partners was much lower. Among men, non-consistent condom use with casual partners was more prevalent if they had been abroad for a longer time, condoms were not taken along from The Netherlands, the country where they were posted was Asian, and the estimated HIV prevalence among the local population was lower. Among the women, non-consistent condom use was more prevalent if condoms were not taken along, and if they did not have the intention before departure to have sex abroad. Of the persons from whom blood could be obtained, one man was HIV-positive. Another man who refused to participate in the study indicated that he was HIV-positive., Conclusions: Although 23% of the expatriates had unprotected sex with partners from endemic areas, very few HIV infections were found. In comparison with a previous study among this population carried out in 1987-1989, which found five out of 1968 expatriates to be HIV-infected, consistent condom use with casual local partners did increase considerably (from 21 to 67%). However, health education is needed to reduce the risk of HIV infection, which should emphasize the sociocultural differences in sexual practices.

Within a surveillance programme in a Regional Public Health Laboratory anonymous information on HIV test, requesting physician and tested individual is automatically selected, regardless of test result. Thereby, personal identifiers are transformed into unique but meaningless numeric codes. Besides, requesting physicians receive a questionnaire on indication for testing (response 87%). Between April 1989 and June 1993 12,219 HIV tests were performed in 10,972 individuals. The percentage of positive tests (2.1%) was twice the percentage of positive individuals (1%). No increase in number of new infections was observed over time. Of individuals, 41.6% were tested due to third party requests (mainly insurance): HIV was demonstrated once (0.03%). Among the remainder, with medical indications, seroprevalence was 1.4%. At relatively little expense, we were able to provide valid information about patterns of HIV-testing and HIV seroprevalences among people tested in routine medical practice. Prevention of double counts proved to be important. Extension to other Dutch areas is expected.

Objectives: To assess the prevalence of HIV infection among intravenous (IDU) and non-intravenous drug users in Heerlen and Maastricht (Southern Netherlands), to detect subgroups of IDU with a higher risk of HIV infection, and to assess the risk of further spread of HIV., Design: Cross-sectional study., Setting: Heerlen, Kerkrade, Brunssum and Maastricht, the Netherlands., Methods: Between August 15 and November 25, 1994, a saliva specimen and a short questionnaire were obtained from 449 drug users (340 IDU) in Heerlen (and environs) and Maastricht. Participants were recruited through methadone care (54%), syringe exchange (16%), a street prostitution project (3%), street recruitment (23%) and other drug users (4%)., Results: Of the 340 IDU 33 were infected (prevalence: 10% (95% confidence interval: 7-13)), among the 109 non-IDU no infections were found (0% (0-3)). IDU making use of the syringe exchange had a higher prevalence (odds ratio 3.13 (1.37-7.61)). In logistic regression analysis, this finding could not be explained by selection on more risky injecting. One in five currently injecting IDU reported having used someone else's used needle or syringe in the last 6 months. One in five IDU had a non-drug user as steady sexual partner. In sexual contacts between steady partners condom use was low. On the basis of self-reported serostatus it appeared that some infections have taken place in the last two years., Conclusions: The prevalence of HIV infections among IDU in Heerlen and Maastricht is about 10%. IDU using the syringe exchange have a higher prevalence. This means this prevention reaches the high-risk group, but probably can not avoid all infections. The risk of further spread among IDU is high. The risk of spread to non-IDU and non-drug users is present.

In this study it was assessed whether homosexual men who practiced unprotected anogenital intercourse with steady and non-steady partners subjectively perceived their behaviors to be risky. Data were collected from 165 homosexual participants in an ongoing cohort study who reported unprotected anal sex. A variety of psychological factors which could possibly explain why some men were at risk but did not perceive their behavior as such, were investigated. This study showed that the majority of men who engaged in sexual risk behaviors within their primary relationship did not subjectively appraise their behavior as risky. The factors found to explain this discrepancy were not having had sex with a partner known to be HIV infected or to have AIDS (for couples of unknown serostatus) and not having had friends or relatives who were ill or had died (for seronegative couples). Homosexual men who had unprotected anal sex with casual partners generally were aware of the risk involved in their behavior.

The risk for dentists to acquire HIV infection at work is low but not neglectable. Needlestick injuries are among the most hazardous events in this respect. Prevention of these injuries will considerably reduce the risk of occupational HIV infection in dentistry.

In order to study the prevalence of human immunodeficiency virus (HIV) infections and related risk factors, Dutch expatriates returning from sub-Saharan Africa were asked to complete a questionnaire on sexual, occupational and other risk factors, and to donate a sample of blood to test for antibodies against HIV. The 1968 participants were workers of various professions and their family members over 16 years of age posted in sub-Saharan African countries by Dutch governmental, non-governmental and commercial organizations for at least 6 months cumulative time between 1 January 1979 and 1 January 1990. Antibodies against HIV-1 were found among 4 of 1122 men (0.4%) and 1 of 846 women (0.1%). The woman and 3 of the men had had sexual contact with African partners and had been treated for sexually transmitted diseases, 2 of these 3 men also had an African life partner. One man reported occupational exposure only. Of the 1968 participants 89 men (7.9%) and 18 women (2.1%) lived with an African partner; 344 men (30.7%) and 111 women (13.1%) had heterosexual contact with other African partners. Only 22.3% (men) and 18.6% (women) of casual sexual contacts with African partners were always protected by a condom. Two hundred and thirty-two of 408 (56.9%) (para)medics reported needlesticks. Groups at risk of HIV infection through sexual exposure were identified using logistic regression models. In conclusion, the observed prevalence of HIV-1 is low. However, unprotected sexual contact with African partners and needlestick accidents were common. This study underscores the continuous need for health education of expatriates on the risks of transmission of HIV in Africa.

A literature review revealed 33 reports of health care workers who have contracted HIV infection as a result of their work. Four of these were expatriate doctors who had worked in Africa. The commonest mode of transmission was needlestick injury, but several infections acquired through contact or skin or mucous membrane with infected blood have been reported. In this paper we outline how the risk of HIV infection in a health care worker can be estimated for a given number of exposures. The formula is based on the known likelihood of transmission per needlestick, the seroprevalence rate among patients, and the number of needlestick injuries that occur. We also suggest a list of measures by which the risk of HIV transmission to hospital staff can be minimized.

In the Netherlands by the 1st of January 1990 1074 AIDS patients have been reported to the Department of the Chief Medical Officer. In the last few years the proportion of intravenous drug users increased and the proportion of homo/bisexual men decreased. After adjustment for the effect of delay in reporting the total number of AIDS patients by 1st January 1990 is estimated to be 1173. It appears that the reporting delay outside Amsterdam is longer than in this city. The time required for doubling of the half-yearly incidence of new AIDS patients (doubling time, dt) increased from 9 months in the beginning of the epidemic to 34 months. It is expected on the assumption of constant dt that 1120 new AIDS patients will be diagnosed in 1990 and 1991 together. The present growth among the homo/bisexual men (dt 34 months) is smaller than the one among the intravenous drug users (dt 23 months). The growth in Amsterdam (dt 36 months) is less than that in the rest of the Netherlands (dt 32 months). Based on the course of the AIDS epidemic the number of HIV infected (including the AIDS patients) is estimated as 9,000-12,000 by the 1st of January 1990.