Search

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.

Background: The long average incubation time from HIV infection to AIDS makes it difficult to estimate recent HIV transmission from AIDS incidence data. Age-period-cohort (APC) analysis can separate out the effects of age, calendar time and birth cohort to provide a clearer picture of transmission trends., Methods: AIDS incidence data from 1981 to 1994 among intravenous drug users (IDU) for 12 Western European countries were used. Yearly incidences per 100,000 population or 100,000 person-years were calculated by age at diagnosis and 5-year birth cohort (1950-1954, 1955-1959, 1960-1964, 1965-1969 and 1970-1974), and corrected for reporting delay. Incidence patterns were compared between birth cohorts and countries., Results: For most countries the impact was greatest on the cohort born 1960-1964. Comparing incidence patterns in the 1965-1969 to 1960-1964 cohorts suggest the epidemic has plateaued at low to intermediate levels in Austria, Greece and the North-Western European countries, and at high levels in France, Italy and Switzerland. For most countries transmission amongst the 1970-1974 as compared to the 1965-1969 cohorts could not be assessed due to small numbers and short follow-up time. In Spain the epidemic was uncontrolled with a high incidence among recent birth cohorts. In Portugal the epidemic was still at an early and expanding phase., Conclusions: The APC analysis revealed large country differences in the dynamics of the HIV/AIDS epidemic among IDU. Full interpretation of these differences is dependent on information from other sources about the local public health response and trends in drug injecting behaviours. Earlier introduction of the virus and higher prevalence of injecting drug use may explain some of the generally higher incidence in Southern European countries, but the larger part of it is most likely explained by local characteristics of drug users, such as younger age and more frequent sharing of needles and syringes, and a less effective public health response.

Among people who work abroad, sexual activity and therefore the risk of HIV infection appear to be relatively high. Little is known about the factors that influence sexual conduct when staying abroad, separated from their usual social environment. This is why 55 expatriates who had been sexually active in AIDS endemic areas were selected for an in-depth interview from the original sample of 864 Dutch expatriates participating in a study on sexual behaviour and HIV infection. The social and cultural context in which the sexual contacts took place was addressed in these interviews. Qualitative analysis of the data led to the identification of four styles with regard to the meaning of and motivations for having sex abroad: 'the unprepared', 'the fanatical', 'the unaffected' and 'the slightly accessible'. These styles are described separately and attention is paid to the association of these styles with protection behavior.

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.

Objective: To document the recent developments in the course of the AIDS epidemic in the Netherlands, 1982-1995., Design: Descriptive., Setting: National Institute of Public Health and Environment, Bilthoven, Municipal Health Service, Amsterdam, and Inspectorate of Public Health, Rijswijk, the Netherlands., Method: Based on the new AIDS patients reported to the Inspectorate of Public Health, the incidence figures were calculated by risk group (homo/bisexual men, intravenous drug users and heterosexual men and women), by birth cohort defined by 5 successive years of birth, and by nationality, in order to characterise sub-epidemics., Results: Among homo/bisexual men AIDS incidence has been stabilizing in recent years. Among intravenous drug users and heterosexuals incidence continues to rise but at a low level compared with homo/bisexual men. Among homo/bisexual men and intravenous drug users mean age at AIDS diagnosis is rising in conjunction with reduced incidence among young persons born in 1965-1969 when compared with the incidence among persons born in 1960-1964 when at the same age. By contrast, among heterosexuals a decline in mean age at diagnosis is observed and this decline coincides with undiminished rise of incidence among persons born in 1965-1969. Among heterosexual patients an increasing and disproportionate number have the nationality of a sub-Saharan African country., Conclusion: Future AIDS incidence among homo/bisexual men and intravenous drug users will probably be lower than it currently is. Regarding heterosexuals the undiminished growth of the number of young AIDS patients and the increasing proportion of patients from abroad make such an assessment more difficult.

Objective: Description of the epidemiology and transmission categories of AIDS in the Netherlands., Design: Descriptive., Setting: The Netherlands., Method: Analysis of all registered AIDS patients until 31 December 1993. Trends in the composition of this population were studied with respect to age and sex, risk groups, geographic distribution across the country, heterosexual transmission, AIDS-defining diseases and reporting pattern., Results: From the first patient in 1982 until December 31, 1993, a cumulative total of 2912 patients was diagnosed and reported in the Netherlands (2995 when corrected for reporting delay). The numbers of reported AIDS cases in the Netherlands are smaller than previously predicted by mathematical models. The proportion of homosexual men in the incidence of AIDS dropped from 89 to 73 per cent, the proportions of intravenous drug users and heterosexual transmission rose to 11 per cent each. Patients in the category of heterosexual transmission are mainly individuals from countries where heterosexual contact is the dominant mode of transmission and their sex partners, and to a lesser extent the sex partners of intravenous drug users (whether or not in relation to prostitution). The proportion of women is rising (229 patients or 8 per cent by December 1993), with most cases transmitted initially by intravenous drug use but later by heterosexual contact., Conclusion: The number of AIDS cases in all risk groups combined is levelling off. However, more detailed analysis shows that the numbers of cases of heterosexual transmission and those in young homosexual men are still rising. For a better quantitation of the quality of the AIDS data, specific research into underreporting and non-diagnosis of AIDS cases in the Netherlands is warranted.

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.