Changes to pathogen fitness as a result of population growth, ageing and migration

Pathogen fitness is driven by how its human and animal hosts interact with each other and the environment to create patterns of susceptibility and transmission. This project aims to use host, pathogen and environmental data in different geographical settings to understand the drivers of pathogen fitness and how human interventions may affect this. Computational simulations will be constructed using host demography and pathogen transmission models that track fitness as a function of host contact patterns, demographic and susceptibility profiles, and other ecological and environmental drivers.
Rotavirus is globally the most common cause of severe diarrhoea amongst children under the age of 5 years. The development of two vaccines (RotaTeq and Rotarix) in 2006 led to several countries introducing rotavirus vaccination. In general, drastic decreases in rotavirus gastroenteritis cases in countries that implemented the vaccine and a number of economic evaluations worldwide have demonstrated the efficacy and effectiveness of vaccine implementation. Nevertheless, these have mostly been limited to low-mortality high income countries and for 2013 the number of deaths in children under 5 years of age due to rotavirus was estimated to be around 215,000 globally. Moreover, the exact mechanisms involved in the transmission between individuals and in the development of both natural and vaccine induced immunity are yet to be fully understood. This uncertainty has resulted in a number of different modelling approaches for rotavirus transmission. With an increasing amount of pre- and post-vaccination data available, especially in higher income settings, this project aims to investigate these underlying mechanisms and appropriate modelling approaches in more detail.
In recent years, countries in different demographic and temperate settings have been or are beginning to implement vaccination programs. These include a number of lower income countries that are at and have been undergoing different stages of the demographic transition, which involves a shift from high to lower birth and death rates. Some countries have been transitioning rapidly in recent decades, changing the fundamental structures of their populations. Host demographics play an important role in determining the survival and reproduction rate of a pathogen and demographic variation due to population growth, ageing and migration may have drastic effects on these. However, models often simplify the underlying demographic processes by making crude assumptions, as their effects on and interactions with pathogens are not very well understood or frequently overlooked. With a better understanding of modelling rotavirus transmission and vaccine protection, this project will explore the effects demographic variation may have on rotavirus transmission and the prospective impact of interventions in the short and long term in different geographical settings.