How sex acts scale with the number of sex partners: evidence from Chlamydia trachomatis data and implications for control
- Subject Areas
- Computational Biology, Mathematical Biology, Epidemiology, Infectious Diseases, Statistics
- sexual mixing, infection control, Chlamydia trachomatis, parameter inference, mathematical model
- © 2015 Althaus et al.
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2015. How sex acts scale with the number of sex partners: evidence from Chlamydia trachomatis data and implications for control. PeerJ PrePrints 3:e940v2 https://doi.org/10.7287/peerj.preprints.940v2
Mathematical models are frequently used to assess the impact of control interventions for Chlamydia trachomatis and other sexually transmitted infections (STIs). Modeling approaches that stratify the population by the number of sex partners often assume the transmission risk per partner to be constant. However, sexual behavior data suggests that people with many partners share less sex acts per partner than people with fewer partners. This should lower the risk of transmission per partner for highly sexually active individuals and could have important epidemiological consequences for STI transmission. We devise a new epidemiological model that we fit to chlamydia prevalence data from Natsal-2 and CSF, two population-based probability sample surveys of sexual behavior in Britain and France. Compared to a standard model where the transmission risk per partner is constant, a model with realistic numbers of sex acts per partner provides a better fit to the data. Furthermore, the improved model provides evidence for strong assortative mixing among individuals with different numbers of sex partners. Our results suggest that all chlamydia infected individuals with one or more new heterosexual partners per year contribute significantly to ongoing transmission, underlining that control interventions should be aimed towards all sexually active young adults.
This version of the manuscript will be submitted to PeerJ.
Table S1: Sexual activity groups and chlamydia prevalence from the CSF data set
The table provides the sexual activity level (number of new heterosexual partners in the last year) together with the number and proportion of individuals and the chlamydia prevalence in each group.