Biomedical subjects

J A Van Druten

Publications and source records attributed to J A Van Druten.

4 recordsLinked to original sources

PubMed1992

Short and medium term projections of the AIDS/HIV epidemic by a dynamic model with an application to the risk group of homo/bisexual men in Amsterdam.

Several methods exist for short term projection of the numbers of AIDS cases. Some use extrapolation of empirical curves fitted to data up to a given time, whereas others such as the popular method of 'back projection' or actuarial methods also use information about the process. In this paper we describe a dynamic model based on a distributed modelling technique allowing for variability both in infectiousness and in age distribution of the population at risk. Some model parameters are taken from the literature, others are estimated from AIDS incidence data from the homo/bisexual population in Amsterdam. The model described here simulates prevalence and incidence of HIV infection. We present prediction intervals for two years from January 1990 onwards. We discuss three scenarios based on the estimated model, two of which consider early treatment with anti-viral drugs. Given the model and the state of the epidemic in Amsterdam, early treatment intervention must be combined with very drastic measures for reducing infectivity in order to have any serious impact on the course of the epidemic.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Short-term predictions of HIV prevalence and AIDS incidence.

Reports of AIDS cases in Amsterdam up to February 1990 were used to make predictions of future cases up to 1993. Two published methods were applied, which make extrapolations from current cases and simultaneously estimate the extent of delay in reporting. The choice of the exact model greatly influenced the predictions, as did predictions for distinct transmission groups. We present results for the homo/bisexual male group, and the total population of Amsterdam. The AIDS case predictions are used to predict the HIV prevalence using the ratio of HIV prevalence to AIDS incidence and through 'back calculation'. We suggest that the ratio is a simple technique that may be used to estimate HIV prevalence. The estimated number of cumulative HIV infected homo/bisexual males in Amsterdam in January 1990 was between 2100 and 4100 in a total of 2200-4600 infected people.

Acquired Immunodeficiency Syndrome↗

PubMed1990

HIV infection dynamics and intervention experiments in linked risk groups.

A multigroup transmission model is described to study the spread of the human immunodeficiency virus (HIV) in linked risk groups. The model permits simultaneous investigation of the increase in the number of persons infected with HIV in three main risk groups: promiscuous homo/bisexual men (two levels of promiscuity), intravenous drug users (men and women) and promiscuous heterosexual men and women. Three modes of transmission are considered: anal and vaginal intercourse and needle sharing. The high dimensional parameter space is connected with the HIV incidence through a transmission matrix. This matrix summarizes the annual effective contact rates due to the three transmission modes. The model helps to clarify which data are needed to disentangle the relative contribution of the within- and between-group transmission routes. The model can be used to perform theoretical experiments. Given a specification of a baseline, the potential use of the model is illustrated by a simulation describing the effect of blocking the transmission through needle sharing. Reference is made to the HIV/AIDS epidemic in The Netherlands. The results of the study show that the model can play a part in the classification of HIV prevalence patterns in linked risk groups, in the study of the interaction between the main risk groups and in the theoretical evaluation of intervention measures.

Female↗

PubMed1989

Correcting reported AIDS incidence: a statistical approach.

This study is motivated by the time lag between date of diagnosis of AIDS cases and date of reporting, which results in incomplete data about the epidemic. A maximum likelihood procedure has been developed to adjust the actual numbers of diagnosed AIDS cases for reporting delay. If a parametric function for describing past and future incidence is assumed, its parameters and the adjustment for reporting delay can be estimated simultaneously. Data from the WHO Collaborating Centre on AIDS, Paris, are used. Practical problems related to data collection are dealt with.

Acquired Immunodeficiency Syndrome↗