The positive impact of effective therapy on the spread of HIV can be outweighed in the long term if the risk behaviour of men who have sex with men (MSM) increases by at least 30%. These are the findings of research from the University of Amsterdam (UvA) – attained using new computational methods – into the incidence (the number of new cases in a given period) of HIV in Amsterdam among MSM. Using computer simulation, the researchers could predict the spread of HIV among this group of men in Amsterdam. On the basis of this simulation, the researchers found that a reduction in risky behaviour is one of the key control mechanisms of HIV incidence, even in the presence of effective therapy. The research results were published in the leading scientific journal BMC Infectious Diseases on 11 May 2011.
The transmission of HIV through contacts among MSM is one of the main causes of HIV in industrialised countries. MSM still accounts for the highest incidence of Sexually Transmitted Infections, including HIV. In spite of the availability of effective antiretroviral therapy, HIV is increasing among MSM. The Amsterdam Cohort Study (ACS) has tracked the high-risk group of MSM in Amsterdam since 1984. The data from this study has enabled closer research into MSM risk behaviour.
The UvA research, led by Professor of Computational Science Peter Sloot, focused on predicting the spread of HIV among MSM in Amsterdam. To this end, the researchers combined data - using the ‘Complex Agent Network’ model (a new computational epidemic model) - on networks of sexual contacts (casual contact and stable relationships) with data on the dynamics of HIV infection and individual behaviour. Behaviour-related parameters and values were entered into the model. Sloot’s team then studied complex scenarios to determine the conflicting effects of risk behaviour and effective therapy. Better medication leads to less viruses per patient, suggesting a lower risk of transmission during sexual contact. The study shows that a change in behaviour, such as having unsafe sex more often, has a much greater effect on the spread of HIV than previously thought. This change in behaviour can occur, for example, because the patient is feeling healthier as a result of new medication. On the basis of the data obtained, the researchers performed computer simulations and quantitative analysis on the expected number of new cases of HIV.
A. Shan Mei, R. Quax, D. van de Vijver, Y. Zhu and P.M.A. Sloot: ‘Increasing risk behaviour can outweigh the benefits of antiretroviral drug treatment on the HIV incidence among men-having-sex-with-men in Amsterdam’, in BMC Infectious Diseases, 11 May 2011.
Note to editors
For more information contact Prof. Peter Sloot via the email address below.