Open Access Highly Accessed Research article

Modelling the impact of chlamydia screening on the transmission of HIV among men who have sex with men

Maria Xiridou1*, Henrike J Vriend12, Anna K Lugner1, Jacco Wallinga1, Johannes S Fennema3, Jan M Prins2, Suzanne E Geerlings2, Bart JA Rijnders4, Maria Prins25, Henry JC de Vries136, Maarten J Postma7, Maaike G van Veen3, Maarten F Schim van der Loeff25 and Marianne AB van der Sande18

Author Affiliations

1 National Institute of Public Health and Environment, P.O. Box 1, 3720, BA Bilthoven, the Netherlands

2 Department of Internal Medicine, Academic Medical Centre, Amsterdam, the Netherlands

3 STI Outpatient Clinic, Public Health Service of Amsterdam, Amsterdam, the Netherlands

4 Department of Internal Medicine and Infectious Diseases, Erasmus University Medical Centre, Rotterdam, the Netherlands

5 Research Department, Public Health Service of Amsterdam, Amsterdam, the Netherlands

6 Department of Dermatology, Academic Medical Centre, Amsterdam, the Netherlands

7 Department of Pharmacy, University of Groningen, Groningen, the Netherlands

8 Julius Center, University Medical Centre, Utrecht, the Netherlands

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BMC Infectious Diseases 2013, 13:436  doi:10.1186/1471-2334-13-436

Published: 18 September 2013



Recent studies have found high prevalences of asymptomatic rectal chlamydia among HIV-infected men who have sex with men (MSM). Chlamydia could increase the infectivity of HIV and the susceptibility to HIV infection. We investigate the role of chlamydia in the spread of HIV among MSM and the possible impact of routine chlamydia screening among HIV-infected MSM at HIV treatment centres on the incidence of chlamydia and HIV in the overall MSM population.


A mathematical model was developed to describe the transmission of HIV and chlamydia among MSM. Parameters relating to sexual behaviour were estimated from data from the Amsterdam Cohort Study among MSM. Uncertainty analysis was carried out for model parameters without confident estimates. The effects of different screening strategies for chlamydia were investigated.


Among all new HIV infections in MSM, 15% can be attributed to chlamydia infection. Introduction of routine chlamydia screening every six months among HIV-infected MSM during regular HIV consultations can reduce the incidence of both infections among MSM: after 10 years, the relative percentage reduction in chlamydia incidence would be 15% and in HIV incidence 4%, compared to the current situation. Chlamydia screening is more effective in reducing HIV incidence with more frequent screening and with higher participation of the most risky MSM in the screening program.


Chlamydia infection could contribute to the transmission of HIV among MSM. Preventive measures reducing chlamydia prevalence, such as routine chlamydia screening of HIV-infected MSM, can result in a decline in the incidence of chlamydia and HIV.

HIV; Chlamydia trachomatis; Men who have sex with men; Mathematical model; Chlamydia screening