Sex, Infections and Disease Modelling

Written by Fabian Sailer, PhD student, University College London

Most of us might have never heard of disease modelling. Nevertheless, it is an important tool to examine diseases, as it helps us to understand how diseases spread within the population. With the help of disease models decision makers in medicine can compare different interventions, so that they find a way to spend the very limited money in health care most effectively. In my PhD at UCL I focus on the modelling of sexually transmitted diseases.

A noticeable burden on the healthcare system

My disease model includes the most important sexually transmitted diseases within the UK: HIV, Chlamydia, Gonorrhoea and a few others. I defined a sexually transmitted disease as important if it is a noticeable burden to the associated healthcare system. This may be caused by a high number of infected patients or by complicated cases, causing high treatment costs. Based on this definition, I selected the previously mentioned diseases. This selection depends on the setting (e.g. UK), as diseases which are important and warrant research in one country might be negligible in another.

Modelling multiple diseases

You might question why I try to model multiple diseases simultaneously, instead of focussing on one disease model: We know that sexually transmitted diseases do not operate in isolation. For example, a Genital Herpes infection may be regarded as an indicator for another sexually transmitted disease. Practically, this means that a patient presenting with Genital Herpes in a genitourinary medicine (GUM) clinic might also be tested for HIV. In a disease model with only one sexually transmitted disease this connection could not be reflected.

The sexual network of the population

Modelling sexually transmitted diseases is challenging in many aspects. Firstly, sexually transmitted diseases do not appear “out of nowhere” like some forms of cancer. A patient must have had prior sexual contact with another infected person. I therefore need to describe the sexual network of a population to account for different risks, resulting from different sexual behaviour. This means that some people are under a greater risk of catching one or more (as explained earlier) sexually transmitted diseases. Generally, the risk increases if someone changes sexual partners more frequently or has concurrent partnerships.

New perspectives and new ideas

Meeting people interested in this disease model is a crucial part of furthering my PhD and extending my network. I have presented the preliminary results from my research at the Public Health England Conference for Applied Epidemiology in Warwick. The event was a great opportunity to meet with possible users of the disease model, even though I only started my PhD less than six months ago. One of the lessons I learned at the conference was that new perspectives on a familiar topic might lead to new ideas, which is why I am keen to further disseminate my work. I am happy to discuss it with anyone who might be interested in this topic after reading this blog.