The Conventional Wisdom Redux: Stochastic Evolution in Mulit-strain Epidemics

Todd Parsons (University of Toronto)

Thursday 30th August, 2012 16:00-17:00 Mathematics Building, room 325


For a variety of reasons, both theoretical and practical, the evolution of pathogens has a topic of sustained interest for evolutionary ecologists. For a long time, the prevailing theory was that pathogens would evolve towards reduced virulence, towards a less severe impact upon the fitness of their host. A multitude of theoretical studies caused this `conventional wisdom' to be displaced in favour of the notion that pathogens tend to maximize their basic reproductive ratio, R_0, the number of new hosts infected per infected individual. This modern viewpoint is founded upon deterministic modelling; I will present analytical results for a stochastic version of the popular SIR epidemic model, taking into account host demography. I will show including stochasticity complicates the tidy picture presented by the deterministic model, and even suggests that the 'conventional wisdom' may not be completely lacking.

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