Reconstruction and prediction of the HIV/AIDS epidemic among adults in the European Union and in the low prevalence countries of central and eastern Europe

Determining the likely place of HIV acquisition for migrants in Europe combining subject-specific information and biomarkers data

In most HIV-positive individuals, infection time is only known to lie between the time an individual started being at risk for HIV and diagnosis time. However, a more accurate estimate of infection time is very important in certain cases. For example, one of the objectives of the Advancing Migrant Access to Health Services in Europe (aMASE) study was to determine if HIV-positive migrants, diagnosed in Europe, were infected pre- or post-migration. We propose a method to derive subject-specific estimates of unknown infection times using information from HIV biomarkers' measurements, demographic, clinical, and behavioral data. We assume that CD4 cell count (CD4) and HIV-RNA viral load trends after HIV infection follow a bivariate linear mixed model. Using post-diagnosis CD4 and viral load measurements and applying the Bayes' rule, we derived the posterior distribution of the HIV infection time, whereas the prior distribution was informed by AIDS status at diagnosis and behavioral data. Parameters of the CD4-viral load and time-to-AIDS models were estimated using data from a large study of individuals with known HIV infection times (CASCADE). Simulations showed substantial predictive ability (e.g. 84% of the infections were correctly classified as pre- or post-migration). Application to the aMASE study (n = 2009) showed that 47% of African migrants and 67% to 72% of migrants from other regions were most likely infected post-migration. Applying a Bayesian method based on bivariate modeling of CD4 and viral load, and subject-specific information, we found that the majority of HIV-positive migrants in aMASE were most likely infected after their migration to Europe.

A Brief History of Cannabis Policies in Spain (1968–2003)

Spain was one of the first countries in Europe to decriminalize drug use and one of the last to embrace harm reduction. As such, Spain's drug policies often appear to be rather contradictory. In this paper we will review the current status of drug laws and the major drug policies that have been implemented in Spain over the last 25 years concerning cannabis; their demographic, political, and economic contexts; and their apparent consequences. We will follow a chronological approach that outlines every major change that occurred during that period while trying to provide some sociopolitical background. We have divided the period under study into four major phases. Each phase addresses a major political change or shift in the social response to drug-related problems. In this account, we will apply to cannabis policies the conceptual distinctions introduced by MacCoun and Reuter in their recent revision of alternative drug policies (2001), especially their tripartite division between punitive, depenalizing, and legalizing regimes and the associated processes of promotion and commercialization. One essential question that concerns the Spanish case is the relationship between legal changes, their implementation, and long-term oscillations in consumption rates.

Prospects of elimination of HIV with test-and-treat strategy

Recently, there has been much debate about the prospects of eliminating HIV from high endemic countries by a test-and-treat strategy. This strategy entails regular HIV testing in the entire population and starting antiretroviral treatment immediately in all who are found to be HIV infected. We present the concept of the elimination threshold and investigate under what conditions of treatment uptake and dropout elimination of HIV is feasible. We used a deterministic model incorporating an accurate description of disease progression and variable infectivity. We derived explicit expressions for the basic reproduction number and the elimination threshold. Using estimates of exponential growth rates of HIV during the initial phase of epidemics, we investigated for which populations elimination is within reach. The concept of the elimination threshold allows an assessment of the prospects of elimination of HIV from information in the early phase of the epidemic. The relative elimination threshold quantifies prospects of elimination independently of the details of the transmission dynamics. Elimination of HIV by test-and-treat is only feasible for populations with very low reproduction numbers or if the reproduction number is lowered significantly as a result of additional interventions. Allowing low infectiousness during primary infection, the likelihood of elimination becomes somewhat higher. The elimination threshold is a powerful tool for assessing prospects of elimination from available data on epidemic growth rates of HIV. Empirical estimates of the epidemic growth rate from phylogenetic studies were used to assess the potential for elimination in specific populations.

[Trends in the epidemic of Aids cases in Southern Brazil from 1986 to 2008]

OBJECTIVE

To describe trends in the incidence of Aids cases according to age and gender from 1986 to 2008.

METHODS

Analyses of Aids trends according to age group and to gender was carried out Londrina, Southern Brazil. The timeframe was divided into two periods (1986-1995 and 1996-2008). Of the polynomial models, it was the first-degree polynomial model which best explained the Aids epidemic within the two periods. The incidence rate of Aids among men who have sex with other men (MSM), injecting drug users (IDU), heterosexual men and women was calculated.

RESULTS

During the first period, from 1986 to 1995, there was an increase in the incidence of Aids in almost all age groups and the epidemic spread across both sexes (p < 0.001), although this was more marked in men aged 14-39. The second period (1996-2008) did not show a positive or negative statistical increase, indicating that the epidemic had stabilized. A significant fall in the rate for the male 14 to 29 age group was found, with increases of 0.88 and 0.87 for the first and second period respectively. Cases in women aged 50 and over showed a marked increase (p = 0.019). The IDU and MSM groups predominated as the categories with the most exposure, with MSM taking over from IDU in the last three years of the study. From 2000 onwards, incidences in females aged 15 to 49 overtook that of heterosexual men.

CONCLUSIONS

The study showed a decrease in incidence in the younger age groups and stabilization in the other age groups. There is a need for different approaches in order to reach groups with several characteristics due to the increase in the proportion of women and MSM within the exposure categories.

HIV incidence estimate combining HIV/AIDS surveillance, testing history information and HIV test to identify recent infections in Lazio, Italy

BACKGROUND

The application of serological methods in HIV/AIDS routine surveillance systems to identify persons with recently acquired HIV infection has been proposed as a tool which may provide an accurate description of the current transmission patterns of HIV. Using the information about recent infection it is possible to estimate HIV incidence, according to the model proposed by Karon et al. in 2008, that accounts for the effect of testing practices on the number of persons detected as recently infected.

METHODS

We used data from HIV/AIDS surveillance in the period 2004-2008 to identify newly diagnosed persons. These were classified with recent/non-recent infection on the basis of an avidity index result, or laboratory evidence of recently acquired infection (i.e., previous documented negative HIV test within 6 months; or presence of HIV RNA or p24 antigen with simultaneous negative/indeterminate HIV antibody test). Multiple imputation was used to impute missing information. The incidence estimate was obtained as the number of persons detected as recently infected divided by the estimated probability of detection. Estimates were stratified by calendar year, transmission category, gender and nationality.

RESULTS

During the period considered 3,633 new HIV diagnoses were reported to the regional surveillance system. Applying the model, we estimated that in 2004-2008 there were 5,465 new infections (95%CI: 4,538-6,461); stratifying by transmission category, the estimated number of infections was 2,599 among heterosexual contacts, 2,208 among men-who-have-sex-with-men, and 763 among injecting-drug-users. In 2008 there were 952 (625-1,229) new HIV infections (incidence of 19.9 per 100,000 person-years). In 2008, for men-who-have-sex-with-men (691 per 100,000 person-years) and injecting drug users (577 per 100,000 person-years) the incidence remained comparatively high with respect to the general population, although a decreasing pattern during 2004-2008 was observed for injecting-drug-users.

CONCLUSIONS

These estimates suggest that the transmission of HIV infection in Lazio remains frequent and men-who-have-sex-with men and injecting-drug-users are still greatly affected although the majority of new infections occurs among heterosexual individuals.

New method for estimating HIV incidence and time from infection to diagnosis using HIV surveillance data: results for France

OBJECTIVE

To estimate HIV incidence and time between HIV infection and diagnosis of infection.

DESIGN

We devised a new model for estimating the incidence of HIV infection and the time between infection and diagnosis from HIV surveillance data. Our approach takes into account temporal changes in HIV test-seeking behaviors and requires few data on individuals newly diagnosed with HIV (i.e. date of diagnosis and clinical status at diagnosis). Using our new approach, we analyzed data for patients newly diagnosed with HIV in France between April 2003 and December 2008.

RESULTS

The estimated mean time between infection and diagnosis ranged from 37.0 months among men who have sex with men to approximately 53.0 months among heterosexual men. Intermediate values were obtained for injecting drug users and heterosexual women. We estimated that mean times changed very slightly (≤1.2 months) during the period 2004-2007: it shortened among MSM, remained stable among non-French-national heterosexual men, and lengthened in all the other exposure categories. We estimated that the total number of new infections increased, but not significantly, between 2004 and 2007, reaching 7851 [95% confidence interval 5400-9919] in 2007. MSM accounted for the largest number of new infections (38%).

CONCLUSION

HIV continues to spread in France, and the average time between infection and HIV diagnosis remains excessively long. New policies to expand the offer and acceptance of voluntary HIV testing are thus urgently needed. Our method will also be very useful to monitor and evaluate the impact of future HIV testing policies.

Evolution of HCV incidence in drug users in France

Over the last 40 years, the dynamics of hepatitis C virus (HCV) infection in drug users has been affected by the illicit drug market, the health environment including the devastating impact of the HIV/AIDS epidemic which erupted in the 1980s, and the diffusion of substitution treatment beginning in 1995. The purpose of this literature review is to present the dynamics of HCV infection in drug users in France over the last 40 years. Two prevalence studies of HCV infection in the general population were conducted by the French Institute for Public Health Surveillance in 1994 and 2004 and were the touchstone data sources for this analysis. Hypotheses constructed from the findings of these two studies were examined in light of results reported by multicentre prevalence and incidence studies in drug-user populations. The incidence of HCV infection in drug users in France reached a peak in the late 1980s or early 1990s after a lengthy period of epidemic expansion. Implementation of a risk reduction policy enabled a very significant reduction in the incidence of HCV infection in drug users over the last 20 years, leading to incidence figures which are now 10–15% of the 1990 estimate.

Lessons from the History of the Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome Epidemic among Spanish Drug Injectors

In Spain, approximately 10 years passed between the time when human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) harm-reduction programs should have been developed with sufficient coverage to have an optimum impact on public health (before the HIV/AIDS epidemic's explosion in 1984) and the date of their actual implementation. This delay yielded an enormous cost for the country. The introduction of the virus in drug injector networks during a period of widespread diffusion of heroin injection and the lack of political awareness of the growing problem were 2 important factors that contributed to the important diffusion of the HIV infection among Spanish injection drug users. Lessons can be learned that may be of great interest in countries or territories facing similar challenges now and in the future.

Extending backcalculation to analyse BSE data

We review the origins of backcalculation (or back projection) methods developed for the analysis of AIDS (acquired immunodeficiency syndrome) incidence data. These techniques have been used extensively for >15 years to deconvolute clinical case incidence, given knowledge of the incubation period distribution, to obtain estimates of past HIV (human immunodeficiency virus) infection incidence and short-term predictions of future AIDS incidence. Adaptations required for the analysis of bovine spongiform encephalopathy (BSE) incidence included: stratification of BSE incidence by age as well as birth cohort; allowance for incomplete survival between infection and the onset of clinical signs of disease; and decomposition of the age- and time-related infection incidence into a time-dependent feed risk component and an age-dependent exposure/susceptibility function. The most recent methodological developments focus on the incorporation of data from clinically unaffected cattle screened using recently developed tests for preclinical BSE infection. Backcalculation-based predictions of future BSE incidence obtained since 1996 are examined. Finally, future directions of epidemiological analysis of BSE epidemics are discussed taking into account ongoing developments in the science of BSE and possible changes in BSE-related policies.

Lookback investigation of patients potentially exposed to HIV type 1 after a nurse-to-patient transmission

A nurse-to-patient transmission of HIV type 1 was recently documented in a French hospital. The origin of the transmission remained unclear. To inform patients who may have been exposed to the nurse while they had received care, a lookback investigation that included mailings and a viral screening was conducted for 7580 patients. No other case of nurse-to-patient transmission of HIV-1 was identified.

Recent trends in the HIV epidemic among injecting drug users in Northern Italy, 1993-1999

OBJECTIVE

To monitor and describe the time trends of the HIV epidemic among intravenous drug users (IDU) attending drug dependence treatment centres (DDTC) in Northern Italy.

DESIGN

A cohort of all seronegative IDU attending DDTC in Lombardy between 1993 and 1999; all had been tested for HIV at least twice. Periodic sample interview surveys were done to assess risk behaviours.

METHODS

The incidence rates of HIV infection were calculated using the person-year (PY) method and expressed as the number of cases per 1000 PY at risk. Background HIV prevalence was calculated by dividing the number of positive cases by the total number of IDU tested at all DDTC in Lombardy.

RESULTS

Between 1993 and 1999, 135 seroconversions occurred in 7945 subjects followed for 19 671 PY, yielding an incidence rate of 6.9/1000 PY. Ninety seroconversions occurred among the 6563 males and 45 seroconversions among 1382 females (incidence rates 5.5 and 14.0, respectively). Among the males, the incidence of HIV was 4.5 in those aged less than 25 years and 5.8 in those aged 25 years or more. Among the females, the corresponding figures were 21.1 and 10.3. HIV prevalence decreased over time, and it was higher among females. Sexual behaviours at risk were more common among females.

CONCLUSIONS

The incidence of HIV infection among IDU in Northern Italy was stable between 1993 and 1999. The higher incidence and prevalence among females and the different prevalence of risk behaviours between genders suggest an increasing role of heterosexual transmission.

Modeling changes in CD4-positive T-lymphocyte counts after the start of highly active antiretroviral therapy and the relation with risk of opportunistic infections: the Aquitaine Cohort, 1996-1997

After initiation of a treatment for human immunodeficiency virus type 1 infection containing a protease inhibitor, immune restoration associated with increases in CD4-positive (CD4+) T lymphocyte count may be delayed. In a sample of patients who had been prescribed protease inhibitors for the first time, the authors tested to see whether there was a minimal duration of CD4+ cell count increase before the increase had an impact on the occurrence of opportunistic infections. The evolution (difference between time t and baseline) of CD4+ cell count was modeled using a mixed effects linear model. Changes in CD4+ count estimated by this model were then included as time-dependent covariates in a proportional hazards model. Finally, the authors tested for the existence of a CD4+ change x time interaction. The authors used a sample of 553 French patients first prescribed protease inhibitors in 1996 and followed for a median of 16 months. During the first 120 days, there was no association between CD4+ change and the rate of opportunistic infections. After 120 days, each 50-cell/mm3 increase in CD4+ count was associated with a 60% (95% confidence interval: 45, 72) reduction in the incidence of opportunistic infections. These results, based on modeling of CD4+ cell response, at least indirectly reinforce the concept of a delayed but possible immune recovery with the use of protease inhibitors. The findings support the potential for interruption of certain types of prophylaxis against opportunistic infections under reasonable conditions of duration of antiretroviral therapy and sustained CD4+ cell response.

Physician recognition of active drug use in HIV-infected patients is lower than validity of patient's self-reported drug use

A French survey of 325 HIV-infected subjects with a history of injecting drugs allowed us to study the recognition of patients' injection drug use (IDU) by physicians providing HIV-infection care, and to analyze the correlation between patient demographics and incorrect IDU identification. Kappa for concordance of physician's reports of their patient's IDU with patient's declaration was 0.37; concordance was lower among socially vulnerable patients. This contrasted with a nested study of validity of patient's self-report of opioid use: Kappa for patient's declaration of opioid use within the past two days against a biological assay was 0.61, and concordance was higher among socially vulnerable patients. Concordance of physicians' ratings and patients' reports of IDU was not more than fair, even though physicians were knowledgeable about their patient's IDU history. This concordance varied with social status in a way that did not correspond with variations in self-reported opioid use validity, suggesting that identification of active IDU might be partly based on incorrect interpretation of subjective cues.

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.

[Trends in the number of human immunodeficiency virus infected persons and AIDS cases in Spain: 1980-1998]

BACKGROUND

To describe the trend in the number of HIV-infected persons and the number of AIDS cases in Spain between 1980 and 1998.

SUBJECTS AND METHODS

The following information was used: annual incidence of AIDS taken from the National Registry, AIDS deaths taken from the same registry and from the Registry of Vital Statistics, HIV seroprevalence in studies in sentinel populations, HIV incidence in cohorts of exposed persons, and reports of HIV infections in the registries existing in the autonomous communities. We considered three events of interest--HIV infection, AIDS and death--which were related using back-projection and compartmental models.

RESULTS

HIV spread rapidly in Spain during the years 1980. Transmission subsequently declined by more than 50% to figures that probably do not exceed 6,000 new infections in 1998. The incidence of AIDS increased to more than 7,000 new cases in 1994 and has since declined to some 4,000 cases in 1998. The level of AIDS mortality has always been lower than the incidence; it increased up to 1995 and then dropped to less than half in subsequent years. The number of living persons infected with HIV, including AIDS cases, arose until the early years 1990 and has since remained steady at about 125,000 persons. The number of cases of living persons with AIDS has increased continuously, and is estimated at about 19,000 through the end of 1998.

CONCLUSIONS

The recent trend in new infections, AIDS cases and deaths is favourable, while the number of infected living persons remains very high.

Trends in HIV seroprevalence among patients with sexually transmitted diseases in 17 European sentinel networks, 1990-1996. European Study Group

OBJECTIVE

To monitor trends in HIV seroprevalence among sentinel populations of patients with new sexually transmitted disease episodes in 17 networks of 15 European countries.

METHODS

Time trends were estimated by logistic regression for homo-/bisexual men, injecting drug users (IDU) and non-IDU heterosexuals. The networks were included as independent variables to account for different prevalence levels across Europe. Socio-demographic and behavioural data were also included in the model. The interactions of time and each factor in the model were evaluated to determine whether trends differed across networks or population subgroups.

RESULTS

Overall, more than 150,000 sexually transmitted disease episodes were registered in this study. In the European network as a whole, the prevalence decreased significantly among IDU [n = 2619; odds ratio (OR) for annual change, 0.86; 95% confidence interval (CI), 0.80-0.93]. It also decreased among homo-/bisexual men (n = 11,809; OR, 0.92; 95% CI, 0.89-0.94). In both groups, trends did not differ statistically between networks. Among non-IDU heterosexuals (n = 114,024) the prevalence increased significantly (OR, 1.08; 95% CI, 1.04-1.13), especially among women (OR, 1.13) and the time trends differed statistically across networks. A significant increase was observed in four networks, whereas no specific change was detected in the others.

CONCLUSIONS

By applying a standardized protocol, trends in HIV prevalence could be compared across networks and estimated at a more global level. For the validity of HIV trends in such surveys, it is essential to minimize the number of patients not being tested in networks where voluntary testing is required.

The emerging AIDS crisis in Russia: review of enabling factors and prevention needs

Eastern Europe is experiencing increased rates of HIV/AIDS, and the Russian Federation is among the countries with the most alarming case rate increases. Behavioural and biological studies demonstrate that the transmission of HIV in Russia is occurring as a result of injection drug use, homosexual, and heterosexual risk behaviours. Factors that promote risk and therefore enable HIV transmission in Russia parallel those found in other countries, including epidemics of other sexually transmitted infections, economic instability, poverty, and social factors such as gender roles. Research is urgently needed to better understand and forecast the HIV epidemic in Russia, as well as to develop effective interventions to prevent a Russian AIDS crisis.

Drug and alcohol consumption and sexual risk behaviour among young adults: results from a national survey

To study the association of the consumption of alcohol and other psychoactive drugs with sexual risk behaviour for HIV infection, data from a representative sample of the Spanish population aged 18-39 years were analysed. A national household survey was carried out in 1996 using a combination of face-to-face interviews and self-administered questionnaires. The survey included 5253 subjects aged 18-39 years who provided information on alcohol and drug consumption, number of sexual partners and condom use with the steady partner and with casual partners in the 12 months before the survey. Of those surveyed, 27.4% had been drunk at least once and 20.5% had consumed drugs. Both behaviours were associated with male sex, younger age, higher educational level, being single and having had more than one sexual partner. In the logistic regression analysis adjusting for the sociodemographic variables, the greater frequency of drunkenness and cannabis use were associated with having more than one sexual partner. Regular condom use was significantly less frequent among cocaine users and more frequent among opiate users, but was not associated with the use of other drugs. Sexual risk behaviour (i.e. more than one partner and failure to use a condom regularly) was more frequent among persons who had been drunk or used cannabis or cocaine. Excessive consumption of alcohol, and cannabis and cocaine use are independently associated with sexual behaviour involving greater risk of HIV infection or transmission.

Estimating the prevalence of injecting drug users on the basis of Markov models of the HIV/AIDS epidemic: applications to Italian data

This paper addresses some important issues related to the estimation of the extent of injecting drug use. The population of injecting drug (heroin) users in Italy is estimated on the basis of a dynamic model of the health consequences, in particular using AIDS incidence data. The use of the prevalence estimates to monitor the impact of health care and law enforcement interventions is outlined.

Risk of hepatitis C virus transmission to surgeons and nurses from infected patients: model-based estimates in France

BACKGROUND/AIM

The aim of this study was to estimate the annual number of cases of hepatitis C virus transmission from infected patients to uninfected surgeons or nurses due to percutaneous injury during invasive procedures.

METHODS

The risk of transmission was estimated using a model involving three probabilities: A, that a health care worker sustains at least one percutaneous injury during a procedure; B, that 1 to 10% of patients are seropositive for hepatitis C virus; and C, that infection by this virus is transmitted to the Health Care Worker after such exposure. Probability A was estimated from the results of 2 French multicentric prospective trials. Probability C was estimated from the results of 9 international prospective studies. A ten-fold decreased risk was assumed for surgeons who wear gloves and use solid-bore suture needles.

RESULTS

During a single procedure, the estimated probability of hepatitis C virus transmission from an infected patient to an uninfected surgeon ranged from 4.2x10(-5)% to 4.2x10(-4)%, and from 2.98x10(-6)% to 2.98x10(-5)% to an uninfected nurse. For surgeons, the estimated annual cumulative risk of occupational infection ranged from 0.01% to 0.1% (1 in 10000 to 1 in 1000), and for nurses from 0.0054% to 0.054% (1 in 18700 to 1 in 1900).

CONCLUSIONS

Between 2 and 21 surgeons out of a total 20000 are estimated to acquire occupationally-related hepatitis C virus infection, and between 16 and 167 nurses out of a total 300000. These estimates strongly justify introducing preventive measures to protect health care workers from bloodborne infection.

Changes in CD4+ cell count and the risk of opportunistic infection or death after highly active antiretroviral treatment. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine

OBJECTIVE

To study the relationship between the CD4+ cell response after initiation of protease inhibitors and the occurrence of opportunistic infections and survival.

DESIGN

Prospective observational cohort study.

METHODS

HIV-1-seropositive subjects followed-up in HIV centres of Bordeaux University Hospital, Southwest France who were prescribed at least one available protease inhibitor between January and December 1996 were included in this analysis. A Cox model estimated the independent effect of baseline covariates and CD4+ cell response, considered as a time-dependent covariate, on the occurrence of new AIDS-defining opportunistic infection, new AIDS-defining events, new AIDS-defining opportunistic infection or death.

RESULTS

A total of 556 HIV-positive patients were prescribed at least one protease inhibitor: 34% saquinavir, 52% indinavir, and 14% ritonavir. Median CD4+ cell count at baseline was 95 x 10(6)/l and mean plasma HIV RNA was 5.0 log10 copies/ml. After a median follow-up of 230 days, 65 patients experienced a new episode of opportunistic infection, 79 patients experienced at least one AIDS-defining event, and 24 had died. On average, the increase in CD4+ cell count was 42 x 10(6)/l (SD, 74) after a median of 49 days. In the multivariate analysis of opportunistic infection or death, each 50% higher CD4+ cell count at baseline was associated with a 23% reduction [95% confidence interval (CI), 14-30] of risk. Each 50% increase in CD4+ cell count during follow-up was associated with a 9% reduction (95% CI, 2-15) of risk, adjusted for the presence of AIDS prior to protease inhibitor therapy (hazard ratio, 3.76 versus absence of AIDS; P < 0.01) and haemoglobin level (hazard ratio, 0.48 if > 11 g/dl versus <11 g/dl; P < 0.01).

CONCLUSION

Our results show, at least indirectly, how protease inhibitors might produce clinical stabilization. This result may be due to improved functionality of CD4+ cells in patients started on protease inhibitors.

HIV prevalence in pregnant women in Europe: differences in assessment methods and prevalence levels across countries

OBJECTIVE

To describe methods used to assess HIV prevalence and to assess prevalence levels and time trends among pregnant women in various European countries.

METHODS

We used the European HIV Prevalence Database to examine annual HIV prevalence data in pregnant women for the years 1990 to 1996 (20 countries).

RESULTS

In Western Europe, prevalences were generally obtained through unlinked anonymous surveys, whereas in most Central, and Eastern European countries, they were based on testing programs (voluntary or mandatory). Prevalences (per 10,000) were highest (i.e., 10-30/10,000) in large western urban areas including Amsterdam, Barcelona, London, Milan, Paris, and Rome; between 1 and 2 in Scandinavian countries; and down to 0.5/10,000 in Central and Eastern European countries (except Ukraine, 1996: 5/10,000). Prevalences decreased in Rome, whereas they increased in London, the Czech Republic, and since 1995 in Russia and Ukraine; elsewhere, no time trends were detected.

CONCLUSIONS

Methodologic differences and potential biases should be considered when comparing these data. HIV prevalence in pregnant women is useful for monitoring the AIDS epidemic and for assessing and improving prevention. Efforts should be made to offer voluntary counseling and testing to women at risk for HIV and provide treatment to those who are infected.

Methods for estimating HIV prevalence: A comparison of extrapolation from surveys on infection rate and risk behaviour with back-calculation for the Netherlands

OBJECTIVES

To compare HIV prevalence estimates (total number infected) by using extrapolation from surveys on infection rate and risk behaviour (EIR) in specific segments of the population and back-calculation (BC) on reported AIDS cases. To discuss potential sources of bias and error, and to identify areas for improvement of the methodology.

DESIGN

Systematic comparison and epidemiological assessment of data input, underlying assumptions, and output.

METHODS

Low, possibly unbiased and high estimates of HIV prevalence as of January 1996 for homo/bisexual men, injecting drug users. heterosexual men and women with multiple partners, and blood transfusion recipients and haemophiliacs were derived from surveys and continuous data collections on HIV infection rate and risk behaviour in the Netherlands between 1992 and 1996. These were compared with estimates (point and 95 % CI) by empirical Bayesian BC on AIDS cases 1982-1995.

RESULTS AND CONCLUSIONS

The estimate of HIV prevalence by EIR was 13,806 with low and high estimates of 9619 and 17,700, respectively. The HIV prevalence estimate by BC was 8812 (95% CI: 7759-9867). The available data from EIR are too limited for accurate estimates of HIV prevalence. EIR estimates could be improved considerably with more precise data on prevalence of risk behaviours and HIV prevalence rate for homosexual men. More confidence can be put in the BC estimates, but these could be underestimates because of the age effect on incubation time, pre-AIDS treatment and relapse of risk behaviour. BC estimates could be improved by a better representation of the incubation time distribution (including the effect of age there-upon), better data on the effectiveness and uptake of pre-AIDS antiretroviral treatment and prophylaxis of opportunistic infections, and on the level of underreporting.

HIV-1 genetic subtype A/B recombinant strain causing an explosive epidemic in injecting drug users in Kaliningrad

OBJECTIVES

To investigate the molecular epidemiology and genetic structure of the virus strain(s) causing an outbreak of HIV-1 infection in the Kaliningrad province of the Russian Federation and to investigate the relationship of this outbreak to some other emerging HIV-1 epidemics in the countries of the former Soviet Union.

DESIGN

A molecular epidemiological investigation was conducted in the city of Kaliningrad amongst individuals recently diagnosed as HIV-1-positive. Samples were also collected from neighbouring Lithuania and from the Ukraine.

METHODS

Incident and population data was collected from official health statistics in Kaliningrad. A standardized questionnaire was administered to newly diagnosed individuals to assess risk factors for HIV-1 infection. For genotyping, two regions of the virus (env C2-V3 and gag NCp7) were directly sequenced.

RESULTS

The number of newly diagnosed individuals testing seropositive for HIV-1 infection in Kaliningrad rose from less than one per month to more than 100 per month during the period of July-October 1996. A total of 1335 new infections were identified between 1 July 1996 and 30 June 1997. The main reported risk factor for HIV-1 infection (80%) was injecting drug use, in particular with a locally produced opiate. Sequence analysis of patient viruses in Kaliningrad (n = 50) showed that the epidemic was caused by a highly homogenous HIV-1 strain, recombinant between the genetic subtypes A and B. Comparison with subtype A strains prevalent amongst injecting drug users (IDU) in the Ukraine showed that one of these strains was the direct subtype A parent of the epidemic A/B recombinant strain in Kaliningrad.

CONCLUSIONS

The HIV-1 epidemic in Kaliningrad probably started from a single source, with rapid spread of the virus through the IDU population. The origin of the epidemic strain is a recombination event occurring between the subtype A strain virus prevalent among IDU in some southern CIS countries, and a subtype B strain of unknown origin.

[Prevalence of HIV, HTLV, and hepatitis B and C viruses in blood donors in France, 1992-1996]

The prevalence of HIV, HTLV, HBV and HCV infections has been calculated by age and sex of blood donors and not, as generally done, according to the number of donations. This study has been conducted on the basis of two surveys. The first one collected information about the sex and age of the seropositive donors. A second survey, begun in 1992, collected information about the demographic characteristics of blood donors. This population has a higher male to female sex ratio (1:2 versus 1:0) and is younger than the general population. Thus, the prevalence of these viral infections has been determined according to sex, age and type of donors (first-time or repeat) from 1992 to 1996 and the trends have been analysed. The main results are the following: a decreasing prevalence of HIV in first-time donors from 1992 to 1996, more marked in men than in women and in the 18-29 year age group than in the other age groups; a slighter decrease in prevalence of HBV and HCV in first-time donors from 1992 to 1996 with no difference in this decrease between sex and age groups. HBs Ag prevalence in first-time donors was twice as high in men than in women and was highest in donors aged from 40 to 49 years in both sexes. Prevalence of antibodies to HCV in first-time donors was comparable in both sexes but varied greatly with age. In men, a peak was observed in the 30-39 age group and in women, the highest prevalence was seen in the 50-65 age group.

The incubation period to AIDS in injecting drug users estimated from prevalent cohort data, accounting for death prior to an AIDS diagnosis

OBJECTIVE

To estimate the incubation-period distribution (time from seroconversion to AIDS) accounting for death before an AIDS diagnosis (DBAD) in a cohort of injecting drug users (IDU) in Amsterdam, The Netherlands and to compare these estimates with those previously obtained from a contemporaneous study of homosexual and bisexual men in Amsterdam carried out using the same facilities.

DESIGN

Participants in a cohort study begun in Amsterdam at the end of 1985 have scheduled follow-up visits every 4 months. All participants of Dutch nationality and who had two or more follow-up visits before January 1996 from which CD4 measurements were available were included in this study. Data concerning AIDS diagnosis and death were verified through review of national and municipal registries.

METHODS

Because time of seroconversion was unknown for study participants and because IDU are at substantial risk for DBAD, we used a Markov model with CD4-based stages that allows for DBAD. The parameters in this model were estimated using the method of maximum likelihood and confidence intervals were calculated using bootstrap methods.

RESULTS

A total of 173 IDU (134 seroprevalent, 39 seroincident) made 1829 visits. Nearly 10% of the visits were non-consecutive. Forty-five IDU developed AIDS and 25 died without an AIDS diagnosis. We estimated that 24% [95% confidence interval (CI), 17-25%] of IDU die before an AIDS diagnosis. As a result, the median time from seroconversion to AIDS (10.5 years; 95% CI, 9.1-10.7 years) is considerably longer than the median time from seroconversion to death (8.3 years; 95% CI, 7.9-8.5 years). Conditional on survival to an AIDS diagnosis, the median time to AIDS is 8.2 years (95% CI, 7.7-8.7 years). The median survival time after a diagnosis of AIDS is estimated to be 1.0 years.

CONCLUSION

The high occurrence of DBAD in IDU has a considerable influence on estimates of the incubation-period distribution. Progression from seroconversion to death was faster in the IDU cohort than in a cohort of homosexual men in Amsterdam (median, 8.3 years and 9.6 years, respectively). However, progression to AIDS conditional on survival to an AIDS diagnosis seems to be similar in both the IDU cohort and in the cohort of homosexual men (median, 8.2 years and 8.3 years, respectively).

Time trends in HIV infection among pregnant women in Europe

OBJECTIVE

To estimate time trends in HIV prevalence among pregnant women delivering livebirths in 14 European countries using a uniform methodology.

METHODS

A form of back-projection was used to estimate HIV prevalence among pregnant women based on reported cases of AIDS due to perinatally acquired HIV infection. The method used estimates the rate of progression to AIDS in children with HIV, and the rate of transmission of HIV from mother to child, derived from published studies.

RESULTS

The prevalence of HIV among pregnant women delivering livebirths was estimated to be highest in Spain (2.61 per 1000 livebirths in 1992-1993), relatively high (> or = 0.3 per 1000 livebirths) throughout the period 1984-1993 in France, Italy and Switzerland, and low (< 0.2 per 1000 livebirths) in Germany, The Netherlands and Scandinavia. There were large and statistically significant increasing trends in the estimated HIV prevalence among pregnant women in Portugal (an estimated 77% increase per 2-year period), Spain (40% increase) and the United Kingdom (77% increase; all P < 0.001). Statistically significant increasing trends of a smaller magnitude were estimated for France (24% increase) and Italy (23% increase; both P < 0.001).

CONCLUSIONS

Sharp increases in HIV prevalence among pregnant women were estimated for several European countries, whereas in other countries no trends in the estimated prevalence were detected.

The HIV epidemic associated with injecting drug use in Europe: geographic and time trends

OBJECTIVES

To evaluate the magnitude and trends of the HIV epidemic associated with injecting drug use in Europe.

METHODS

AIDS cases associated with injecting drug users (IDU) diagnosed through 1995 were analysed, including IDU, homo-/bisexual IDU, heterosexual partners of IDU and children whose mothers were IDU. HIV seroprevalence studies among IDU were reviewed.

RESULTS

Of the 171,932 cumulative AIDS cases, 73,119 (43%) were IDU-associated (IDU, 89.0%; homo-/bisexual IDU, 3.5%: heterosexual partners of IDU, 6.2%; children with IDU mothers, 1.4%). Over 90% of IDU-associated cases were concentrated in south-western European countries with considerably higher rates in Spain (124 cases per million in 1995) than elsewhere (Italy, 68 per million; Portugal, 42 per million; France, 38 per million). During 1990-1995, incidence increased at an average annual rate of 11% overall and > 23% in central and eastern Europe; overall, incidence increased in older persons (12%) while decreasing in those aged 13-24 years (by 6%). HIV prevalence in IDU showed considerable geographic variation across and within countries. In several countries of western Europe, prevalence decreased. In the former Soviet Union, large HIV outbreaks have recently been detected among IDU through systematic HIV testing (e.g., in Ukraine, 6750 HIV infections were diagnosed in IDU tested during 1995-1996).

CONCLUSIONS

IDU have played a major role in the spread of HIV in Europe. In several western European countries, the incidence of HIV acquired through drug use has declined following high rates in mid-1980s. Studies to assess current transmission are needed and prevention efforts must be maintained. In eastern Europe, emerging epidemics reinforce the urgency for prevention.

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.