20 June 2016

PhD student Ka Yin Leung developed a mathematical model for the spread of STD’s

The more partners at the same time, the higher the risk of an HIV epidemic

Having multiple partners at the same time can substantially contribute to an STD epidemic. This is evident from the PhD research conducted by Ka Yin Leung. She used mathematical models to understand what influence relationship structures, such as having multiple partners at the same time, can have on the spread of sexually transmitted diseases in a network. Leung will obtain her doctorate on 27 June at Utrecht University for her research, supervised by epidemiologist Mirjam Kretzschmar (UMC Utrecht and RIVM) and mathematician Odo Diekmann (Utrecht University).

“STD’s can easily be put into a mathematical model”, explains Leung. “In general, people have a limited number of sexual relationships, that mostly last for a longer period of time. It is important to incorporate these relationships into models of the spread of STD’s. This is in contrast with something like flu, whereby you can become infected by anyone you encounter on a day-to-day basis, and where relationship structures are less important. Leung’s research helps us to better understand STD’s, and can therefore eventually contribute to the prevention of STD epidemics.

Dynamic network

Leung developed and analysed mathematical models for dynamic sexual networks and the spread of STD’s via these networks. She formulated a model for a network in which individuals could have multiple partners at the same time. The network is dynamic, because relationships are formed and break apart and because people enter and leave the population. Leung also modelled an infectious disease, that could spread across the network via relationships between infectious and susceptible individuals. Leung analysed the model by characterising various properties of the infection dynamics, such as the average number of infections that a carrier of the disease causes and the stable number of individuals with the disease in the long term.

Infectious disease dynamics

Leung used mathematical models to get a better qualitative insight into the impact of relationship structures on the spread of STD’s. Here, she focused particularly on the HIV epidemic in Sub-Saharan Africa. Analysis of infectious disease dynamics shows that having multiple partners at the same time can substantially contribute to an STD epidemic. This theoretical research does not necessarily constitute a statement about the actual situation with regards to HIV in Sub-Saharan Africa. The most important contribution of Leung’s research is the development of flexible models for the spread of infectious diseases in dynamic networks, and thus also the ability to eventually better understand infectious diseases.