Math Biology Seminar: Branching Processes in Evolutionary Epidemiology

The emergence of novel infectious diseases has become a major public health concern, with zoonotic diseases such as avian and swine flu providing prominent examples. Although initially poorly adapted to their new host, such pathogens have the potential to adapt over the course of a chain of transmissions and thus may cause a major epidemic. In this talk, I will present a branching process model of the between-host spread of an evolving pathogen. This stochastic model allows us to address the probability of events such as evolutionary steps and major epidemics, and identify risk factors influencing these probabilities.

 

I will begin by reviewing single-type branching processes as applied to disease spread, and then introduce a multi-type process that can capture several strains of pathogen which may arise. Through a fairly general framework, we can investigate the impact of contact distribution in the host population and of the mutational pathway(s) among pathogen strains on the probability of pathogen emergence (adaptation and non-extinction). Time permitting, I will also present preliminary results on the probability of specific strains arising and the distribution of time to extinction or evolution.