The influence of sexually active non-reproductive groups on persistent sexually transmitted diseases

Abstract

We describe several population models exposed to a mild life-long sexually transmitted disease, i.e. without significant increased mortality among infected individuals and providing no immunity/recovery. We then modify these models to include non-reproductive groups consisting of those isolated from sexual contact and those who are sexually active but infertile due to choice, medical or other reasons. We analyse the potential effect on the dynamics of the population. We are interested in how the isolated class may curb the growth of the infected group while keeping the healthy population at acceptable levels. We also analyse the difference between being sexually active and abstained within the non-reproductive class and its impact on the epidemic reproductive number and the nature of the bifurcation around the disease-free equilibrium. We provide a comparison with our models introduced in a previous article, which include only the isolated from sexual contact class.

The role of sexually abstained groups in two-sex demographic and epidemic logistic models with non-linear mortality

“…We can, therefore, establish conditions on the parameters so that This result is similar to the one obtained in our previous paper (Maxin and Milner, 2007) involving SI-type one-sex models. In that case the transmission process involved only one parameter, l, the force of infection coefficient.…”

“…We used the demographic model with isolation from reproduction to analyze the impact of abstaining from sexual activity on the evolution of a persistent sexually transmitted disease. This was a continuation of our previous work using one-sex S2I type models (Maxin and Milner, 2007). We found that, just as in the one-sex case, the isolation from sexual activity has both a demographic and an epidemiological impact in the sense that the isolated group can induce a stable disease free equilibrium in an otherwise endemic population.…”

“…We omitted this class to keep our model as simple as possible and to compare the results with those from one-sex models analyzed in Maxin and Milner (2007). The distinction between sexually active and non-reproductive and sexually inactive will be treated in an upcoming paper using both one-sex and two-sex models.…”

“…The main question that we address is: how much and in what form isolation from sexual contact by some proportion of individuals may affect two important aspects of a real population with a sexually transmitted disease: its growth as a population and the spread of the disease. Previous work addressed this question from a demographic perspective only (Milner, 2005) and from an epidemiological one using S2I type exponential and logistic one-sex models (Maxin and Milner, 2007).…”

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“…Our next objective related to the present research is to investigate if similar results can be obtained using two-sex models. The influence of sexually abstaining groups on STD dynamics has been analyzed in [Maxin 2009;Maxin and Milner 2009] using a gender structured logistic model. We intend to extend that model to include vertical transmission.…”