Back-calculation by birth cohort, incorporating age- specific disease progression, pre-AIDS mortality and change in European AIDS case definition. European Union Concerted Action on Multinational AIDS Scenarios.

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.

A birth cohort analysis of AIDS in Europe: high incidence among young persons at risk.

OBJECTIVES: To study trends in AIDS incidence in Europe by age and year of birth. DESIGN: Age-period-cohort analyses were adopted to distinguish the different time factors of calendar year, age and year of birth. METHODS: Non-aggregate AIDS incidence data from 12 European countries (1978-1994) were adjusted for reporting delay and expressed per unit of population (per 100000 persons or 100000 person-years). Age-specific incidence patterns (absolute level and rate of increase) were compared between 5-year birth cohorts for homo-/bisexual men, injecting drug users (IDU) and heterosexual contact cases. RESULTS: Mean age at diagnosis increased strongly amongst IDU, but less so among homo-/bisexual men and heterosexual contact cases. Of a total 110646 reported cases (116311 after adjustment for reporting delay), 87167 (78.8%) were among people born in 1950-1974 [91951 (79.1%) after adjustment for reporting delay]. The relative impact on specific birth cohorts differed strongly by exposure group. Incidences at age ranges of 20-24 and 25-29 years among cohorts born in 1965 and after were about the same level (homo-/bisexual men, IDU) or higher (heterosexual contact cases) than older birth cohorts when these were in the same age range; rates of increase were less among homo-/bisexual men and IDU, but higher among heterosexuals. There were large differences between counties. CONCLUSIONS: Overall, AIDS incidence among cohorts born in 1965 and after is about the same level (homo-/bisexual men, IDU) or higher (heterosexual contact cases) than older cohorts when these were in the same age range. Rates of increase of AIDS incidence curves suggest reduced HIV transmission amongst the most recent cohorts of homo-/bisexual men and IDU, but among young heterosexuals the epidemic is still expanding.

Cost effectiveness of expanded antenatal HIV testing in London.

BACKGROUND: Recently the Department of Health announced the introduction in England of voluntary universal HIV screening in early pregnancy to prevent vertical transmission. New data have shown the importance of HIV infection in infants born to mothers who were HIV-negative in early pregnancy and who acquired HIV later in pregnancy or during lactation. This requires consideration of repeat testing in late pregnancy and testing of partners of pregnant women (expanded antenatal HIV testing). OBJECTIVE: To estimate cost effectiveness of expanded antenatal HIV testing in London (England) within the framework of universal voluntary HIV screening in early pregnancy. DESIGN: Incremental cost-effectiveness analysis. METHODS: Cost estimates of service provision for HIV-positive children and adults by stage of HIV infection were combined with estimates of health benefits for infants and parents and with costs of counselling and testing (testing costs). In a pharmacoeconomic model cost effectiveness was estimated for expanded antenatal HIV testing in London for universal and selective strategies. RESULTS: Testing costs in the plausible range of pounds sterling 4 to pounds sterling 40 translate into favourable incremental cost-effectiveness estimates for expanded antenatal HIV testing in London which is already at low numbers of vertical transmissions averted per 100000 pregnant women who test HIV-negative in early pregnancy. Favourable cost effectiveness for universal expanded testing would require testing costs in the lower range, whereas selective expanded testing may produce favourable cost effectiveness at testing costs close to pounds sterling 40. CONCLUSION: Based on pharmaco-economic considerations, the authors believe that implementation of expanded HIV testing in London should be considered.

Economic impact of the AIDS epidemic in the European Community: towards multinational scenarios on hospital care and costs.

OBJECTIVE: To underpin multinational public-health HIV/AIDS strategy planning in the European Community (EC) by integrating national studies on HIV/AIDS in scenario analysis. METHOD: Three types of data are used: routine surveillance data, information on disease progression and observational studies on the economic impact. The HIV/AIDS epidemic is simulated using two models (MIDAS and PC-Based AIDS Scenarios). Selected simulations, consistent with surveillance data, are connected to economic impact (hospital-bed needs and annual hospital costs for AIDS patients). Parameter values expressing per person-year economic impacts are derived from a structured review of publications on economic aspects of AIDS. RESULTS: Evaluation of published studies on hospital resource use and costs in EC countries shows that there are significant differences between both countries and studies, even after conversion to similar measures (for example, using purchasing power parities). These differences are partly due to factors such as the composition of the patient population. Differences in methodology may also have influenced the results. Economic impact is analysed for combinations of three factors; survival time after AIDS diagnosis, hospital inpatient days needed per person-year and corresponding hospital costs per person-year. All scenarios indicate 1995 hospital-bed needs above the 1990 level of 5400 beds. Hospital cost projections for 1995 vary (up to US$1050 million). CONCLUSIONS: (1) For economic impact assessment, there are important gaps in epidemiological and economic data, and in the methods for linking these. (2) Standardization of studies on the resource use and costs of HIV/AIDS is necessary to provide a sound basis for multinational scenarios. (3) Preliminary multinational scenarios show that by 1995 hospital-bed needs for AIDS might reach 0.45% of all hospital beds available in the EC, and that hospital cost projections for AIDS in that year will range from 0.15% to 0.30% of EC health-care expenditure.

Pharmacoeconomics of influenza vaccination in the elderly: reviewing the available evidence.

Most western countries have influenza vaccination programmes for citizens aged > or = 65 years. This paper reviews the available evidence on whether elderly influenza vaccination is worthwhile from a pharmacoeconomic point of view. A search on Medline and EMBASE resulted in a primary selection of approximately 100 studies on the pharmacoeconomics of influenza vaccination in the elderly. Further selection of studies to be included in the review was based on several criteria such as original research paper, cost-benefit or cost-effectiveness analysis. influenza vaccination in the elderly, and publication between 1980 and 1999. The 10 studies included in the final selection were evaluated regarding 3 main aspects: benefit-cost ratio and cost-effectiveness ratio; vaccine effectiveness; and relative costing of the vaccine. In general, differences in benefit-cost ratios could be explained by differences in effectiveness and relative costing of the vaccine. Considering the available pharmacoeconomic evidence, influenza vaccination of the elderly in western countries is an intervention with favourable cost-effectiveness in terms of net costs per life-year gained and even has cost-saving potential. In particular, influenza vaccination among elderly people at higher risk, such as the chronically ill elderly, is generally found to be cost saving. Relatively favourable cost-effectiveness among non-high-risk elderly justifies universal influenza vaccination of the elderly from a pharmacoeconomic point of view.

Current and future medical costs of asthma and chronic obstructive pulmonary disease in The Netherlands.

The aim of this study was to estimate the healthcare costs of asthma and chronic obstructive pulmonary disease (COPD), in the Netherlands, in 1993. Also studied was the future development of these costs, as a result of ageing and possible changes in smoking behavior. A prevalence-based cost-of-illness approach was used to estimate direct medical costs. Age- and gender-specific data were obtained from representative national registries and large, representative surveys. To model future costs, cost estimates were linked to an epidemiological model based on a dynamic multi-state lifetable. It describes 1 yr changes, from one state to another, that result from ageing, birth, migration, incidence, recovery from asthma and death due to asthma, COPD or other causes, and starting or quitting smoking. Three different scenarios were modelled: 1) a reference scenario which primarily predicts the impact of ageing. 2) an 'attainable' smoking reduction scenario and 3) an 'extreme' smoking reduction scenario. Direct medical costs were estimated to be $US 346 million in 1993. With increasing age, the relative importance of asthma in total asthma and COPD costs decreased from 91% to less than 4%. Annual costs per patient were estimated to be $US 499 for asthma and $US 876 for COPD. The breakdown of costs differed considerably between asthma and COPD. The reference scenario predicted the costs to increase by 60% to reach $US 555 million by 2010, COPD prevention as modelled in the second and the third scenario reduced the projected cost increase from 60%, to 57% and 48%, respectively. Together, the direct costs of asthma and COPD represent 1.3% of the Dutch health care budget. The breakdown of the costs shows different patterns for asthma and COPD. The costs of these diseases are expected to increase by 60% in the near future. In the short run the impact of smoking reduction on reducing this increase is relatively small, but it will be greater in the long run.

Cost-effectiveness analysis of pneumococcal vaccination for elderly individuals in The Netherlands.

OBJECTIVE: To assess the cost effectiveness (net costs per life year gained) of pneumococcal vaccination of elderly individuals aged 65 years and over in The Netherlands. DESIGN AND SETTING: A pharmacoeconomic analysis was conducted from the healthcare perspective in The Netherlands. The gender- and age-specific modelling framework linked epidemiological aspects of invasive pneumococcal disease (e.g. incidence, mortality, life years lost) to vaccination and hospital resource use. To derive 90% confidence limits for net costs per life year gained a stochastic analysis was performed. INTERVENTION: Pneumococcal vaccination in the elderly with the 23-valent vaccine. Effectiveness of the vaccine in preventing invasive pneumococcal disease was derived from international studies. MAIN OUTCOME MEASURES AND RESULTS: Pneumococcal vaccination in the elderly was not found to be cost saving. At baseline, stochastic and univariate sensitivity analysis net costs per life year gained were estimated to be between 6000 and 16,000 euro (EUR) [EUR1 = 1.1 US dollars; cost level 1995]. A scenario analysis on alternative age-dependent vaccination strategies indicated even higher net costs per life year gained, up to EUR28,000 for vaccinating only those elderly aged 85 years and over. CONCLUSIONS: Pneumococcal vaccination is associated with net costs per life year gained of EUR10,100 (at baseline assumptions). These costs are higher than those for influenza vaccination (EUR5500). Our pharmacoeconomic approach, which needs to be considered in conjunction with social, psychological and budgetary issues, is intended to contribute to rational decision-making in healthcare policy.

Economic evaluation of influenza vaccination. Assessment for The Netherlands.

OBJECTIVE: The objective of this study was to determine the costs associated with influenza and the cost effectiveness (net costs per life-year gained) of influenza vaccination in The Netherlands. DESIGN AND SETTING: The economic evaluation comprised a cost-of-illness assessment and a cost-effectiveness analysis, both of which were conducted from the healthcare perspective in The Netherlands. The modelling framework for the economic evaluation linked epidemiological aspects of influenza (e.g. incidence, mortality, years of life lost) to vaccination coverage and healthcare resource use. Healthcare resource use was specified for hospitalisations, general practitioner visits and drugs. INTERVENTION: The intervention assessed in the cost-effectiveness analysis was influenza vaccination. MAIN OUTCOME MEASURES AND RESULTS: The costs of influenza were estimated to be 31 million euros (EUR) for the influenza season 1995/96 in The Netherlands (EUR1 approximately $US1.1). For the extended programme in 1997/98, i.e. all elderly people, the cost-effectiveness ratio was estimated at EUR1820 per life-year gained. Sub-group analysis demonstrated that the programme had a more favourable cost effectiveness among the chronically ill elderly population (cost saving) than among the rest of the elderly population (EUR6900 per life-year gained). CONCLUSION: Influenza vaccination has a cost-effectiveness ratio that is better than or comparable to that of other implemented Dutch programmes in the prevention of infectious diseases.

Social transmission routes of HIV. A combined sexual network and life course perspective.

A combined sexual network and lifecourse perspective is proposed as a basis for reconstructing the sexological infrastructure of HIV dissemination. Necessary data are drawn from a representative sample survey of 1001 adults (age range 18-50 years) in the Netherlands. Heterosexual respondents' behavioural risk level, expressed in the number of unprotected sexual interconnections with primary and secondary partners, is found to be related to both age and relational status, though these variables cannot fully predict risk. While those under 24 years of age are over-represented in the larger components of sexual networks, above 32 years of age there is a small group who follow a lifestyle of regularly changing sexual partners.

The basic reproduction ratio R0 for a sexually transmitted disease in a pair formation model with two types of pairs.

We study a model for pair formation and separation with two types of pairs which differ in average duration. A fraction f of all newly formed pairs have a long duration (denoted by "steady"), the remaining fraction 1-f have a short duration ("casual"). This distinction is motivated by data about the survival times of partnerships in a sociological survey. In this population we consider a sexually transmitted disease, which can have different transmission rates in steady and in causal partnerships. We investigate under which conditions an epidemic can occur after introduction of the disease into a population where the process of pair formation and separation is at equilibrium. If there is no recovery we can compute an explicit expression for the basic reproduction ratio R0; if we take recovery into account we can derive a condition for the stability of the disease-free equilibrium which is equivalent to R0 < 1. We discuss how R0 depends on various model parameters.

Trends in hospital resource utilization by HIV-infected persons, January 1987-June 1990.

Trends in the utilization of various hospital resources by HIV-infected persons between January 1987 and June 1990 have been studied to support health care planning. Data on 126 asymptomatic and symptomatic HIV-infected persons have been recorded at a patient level and analyzed at half-yearly intervals. At a hospital level, increasing utilization trends were observed. At the patient level, a decreasing utilization intensity was measured for admissions, inpatient days, inpatient diagnostic examinations, and outpatient consultations. Increasing utilization intensity was measured for care during admissions. A constant utilization intensity was observed for outpatient diagnostic examinations and inpatient medication days. Use of interventions tended to increase at the end of the study period. Discriminating between trends in the utilization of different hospital resources can improve the management of hospital health care demands of HIV-infected people.

Disease-staging for modelling current and future health-care impact of disease: illustrations for diabetes mellitus and AIDS.

This paper addresses the economic relevance of appropriately staging progression of disease for cost assessment and projection. Illustrations are drawn from two Dutch cost-of-illness studies for Diabetes Mellitus (DM) and AIDS. Our disease-staging specifies a separate late stage to capture terminal high-intensity care for end-stage complications. Data are used from a registration of national hospital resource utilization for DM and from a detailed database on AIDS hospital care and costs. In particular, differences in average length of hospital stay for several potential DM end-stage complications are compared with non-DM patients. Neglecting the separation of a specific late stage is estimated to possibly miscalculate 15-20% of the hospital bed needs for DM and AIDS in the Netherlands. In particular, confidence intervals of future projections for AIDS hospital beds--using respectively staged and non-staged models--do not overlap. AIDS hospital costs are overprojected by almost 11% in the non-staged model. Our estimation of DM hospital bed needs raises the percentage in total Dutch hospital beds from 1.7% (neglecting a specific late stage) to 2.0%. For DM and AIDS an appropriate disease-staging averts structural biases in estimations of bed needs and costs, and therefore benefits the planning of hospital care facilities. Obviously, gathering comparable information and developing similar methodology on other diseases, such as respiratory disease, cardiovascular disease and cancer, is needed and could benefit planning in these fields.

Lifetime hospitalization profiles for symptomatic, HIV-infected persons.

We explored the relationship between the incidence of hospitalization and disease progression in a group of 140 symptomatic, HIV infected patients by linking hospitalizations to the time of diagnosis, the time of death, or both. The relationship could best be described by positively skewed U-patterns or (weak) J-patterns with a high use of resources immediately following diagnosis and preceding death. The lifetime hospitalization profiles differed according to the type of insurance, age, the initial diagnosis in the CDC-IV stage and the length of survival. The results not only confirm general hypotheses posed by other research groups, but also demonstrate the existence of variations among subgroups of patients. The results can be used to improve economic assessments of the impact of AIDS in The Netherlands and the European Union. The method used has the advantage of being based on a bottom-up approach to resource utilization, involving the use pf prospective data for the patients' full lifespans, and can easily be applied to other areas of health services research.

Hospital cost for patients with HIV infection in a university hospital in The Netherlands.

Precise data on the utilization of health care facilities by HIV infected patients are generally not available. Nor are there data on the related cost, effectiveness and efficiency of the treatment provided. This is due mainly to the lack of a suitable method for recording demographic, medical and financial data on individual patients in hospitals. For this reason we have been developing a system of data collection, which provides a detailed cost record of each patient. The application of this system for 52 patients with HIV infection treated in a university hospital over a two-year period showed that for a patient with AIDS the mean cost of inpatient and outpatient hospital services was $19,507 per person-year. For patients with HIV infections other than AIDS the mean costs ranged from $1,769 for CDC III patients to $2,064 for CDC II patients (expressed in 1987 US dollars). Continued operation of the registration system will make it possible to analyze the causal background of costs as well as the cost-effectiveness of the treatment.

AIDS scenarios for The Netherlands; the economic impact on hospitals.

OBJECTIVE: To assess the economic impact of HIV/AIDS on the health care system in The Netherlands. DATA AND METHODS: Two types of data are used: (i) routine surveillance data on AIDS incidence and (ii) information on hospital resource utilisation and corresponding monetary costs. Progression of disease is modelled using a multi-stage model, with stages corresponding to clinical classifications and to different phases of health care need. Economic impact is analysed for all stages in three scenarios: the reference and two alternative scenarios. RESULTS: In the year 2000 hospital bed need would reach 220 beds if yearly new HIV infections in the 1990s remain at the level estimated for the end of the 1980s, and if the intensity of hospital care remains constant. A minimum need of 125 beds is projected if no new HIV infections occur in the 1990s. Hospital costs in 1993 are estimated to amount to 33.8 million ECUs. Scenarios indicate a range of 26.7-50.7 million ECUs for the year 2000 (price level: 1993). The proportion of the costs of hospital inpatient care and cure in total hospital costs increases, whereas the proportion for outpatient services decreases. CONCLUSIONS: Projected hospital bed need of 125-220 for HIV/AIDS in the year 2000 is limited compared to the projections for coronary heart disease and stroke, but approaches that for lung cancer, pneumonia and diabetes. We estimate hospital costs to have been 85% of total health care costs for HIV/AIDS in 1993. In 1993, the estimated proportions in hospital costs are 41% for inpatient care, 20% for inpatient cure and 39% for outpatient facilities. Our scenarios indicate a decreasing share of outpatient costs--possibly to 30% of total hospital costs for HIV/AIDS in 2000--illustrating the growing relative importance of the AIDS stage for the hospital costs. We project hospital costs for HIV/AIDS in 2000 to reach up to 0.53% of projected hospital costs for all diseases. A present value of 38 million ECUs (23%) of hospital costs projected in the reference scenario might be avoidable, during the period 1994-2000. However, with unchanged treatment patterns a present value of 127 million ECUs for hospital costs during the same period is projected to represent unavoidable costs (discount rate: 5%). In The Netherlands, data needs in the field of economic impact assessment of HIV/AIDS especially refer to registrations of non-hospital outpatient resource utilisation and costs.

Hospital care for persons with AIDS in the European Union.

This study estimates the current and future hospital resources for AIDS patients in the European Union (EU), using multinational scenario analysis (EU Concerted Action BMH1-CT-941723). In collaboration with another EU-project ('Managing the Costs of HIV Infection'), six national European studies on the utilization of hospital care for AIDS have been selected to provide the data for our analysis. The selection criteria involve recentness, quality, comparability, accessibility and representativeness. Baseline hospital resource utilization is estimated for hospital inpatient days and outpatient contracts, using a standardized approach controlling for two severity stages of AIDS (chronic stage and late stage). The epidemiological part of the study is based on standard models for backcalculating HIV incidence and projecting AIDS incidence, prevalence and mortality. In the next step, baseline resource utilization is linked to epidemiological information in a mixed prevalence and mortality-based approach. Several scenarios render different future epidemiological developments and hospital resource needs. For the year 1999, hospital bed needs of 10,000-12,700 in the EU are indicated, representing an increase of 20-60% compared to the estimated current (1995) level. The projected range for 1999 corresponds to a maximum of 0.65% of all hospital beds available in the EU. The growth in the number of outpatient hospital contacts is projected to possibly exceed that of inpatient days up to 1.82 million in 1999. Our methodology illustrates that estimation of current and future hospital care for AIDS has to be controlled for severity stages, to prevent biases. Further application of the multinational approach is demonstrated through a 'what-if' analysis of the potential impact of combination triple therapy for HIV/AIDS. Estimation of the economic impact of other diseases could as well benefit from the severity-stages approach.

[Continuous 2-layer suture of the femoral hernia. Initial clinical results with 31 patients]. / Fortlaufender zweireihiger Nahtverschluss der Schenkelbruchpforte. Erste klinische Ergebnisse an 31 Patienten.

In a retrospective study the two-lined continuous suture for the repair of femoral hernia was examined. From 1.12. 1985 till 31.5. 1988 the femoral defect was closed by a continuous two-lined suture 33 times in 31 patients. In almost 50% (16 cases) the hernia was incarcerated, in total 10 surgeons took part. Postoperatively occurred one wound infection and one serom. During a postoperative observation time of 1-28 months up to now no recurrence has been seen. Thus the two-lined continuous suture of femoral hernia seems to use a sure, simple and practical operation technique, that can be used very well in the every-day-practice, also in case of incarcerated hernia.

Universal HIV screening of pregnant women in England: cost effectiveness analysis.

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.

[Registration and cost estimation of clinical and outpatient activities of patients with HIV infection]. / Registratie en kostenschatting van klinische en poliklinische werkzaamheden voor patiënten met HIV-infectie.

The implications of AIDS for health care are unknown. Precise data about the extent to which patients appeal to hospital health care facilities and resulting costs are not available, mainly due to the absence of suitable methods for the registration of demographic, medical and financial data on individual patients in hospitals. In this paper we present the preliminary results of application of a new system which allows such a detailed collection and analysis of data. By evaluating patients with HIV infections treated in the University Hospital Utrecht between January 1, 1987 and July 1, 1988, the mean yearly costs of in- and outpatient treatment of a patient with AIDS (CDC-IV) were found to be Dfl. 40,267.-; those of treatment of patients with other HIV infections ranged from Dfl. 3,629.-(CDC-III) to Dfl. 5,115.-(CDC-II). Comparison of the mean costs for patients who died in that period with those for patients who did not, reveals that patients dead of AIDS would have cost Dfl. 75,289.-yearly and those with AIDS who were alive at July 1, 1988 Dfl. 27,308.-.

[Prognosis concerning HIV-infection and AIDS epidemic in The Netherlands based on mathematical analysis]. / Prognose aangaande HIV-infectie en AIDS-epidemie in Nederland op basis van wiskundige analyse.

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.