Mathematical Biology Seminar Damon Toth, Math Department, University of Utah Wednesday March 25, 2009 3:05pm LCB 215 Investigating causes of seasonality of infectious diseases Abstract: It has long been known that outbreaks of infectious diseases tend to occur according to seasonal patterns. Surprisingly, the mechanisms that drive seasonality remain poorly understood to this day, even for well-studied diseases such as influenza. Mathematical modelers have attempted to shed light on possible mechanisms that drive different forms of periodicity observed in disease incidence, using differential or difference equation models with a periodically varying transmission parameter. I will discuss how ideas from the field of dynamical systems, such as parametric resonance and bifurcation theory, can help explain why different outbreak patterns are observed for different diseases or in different parts of the world. I will present my application of these mathematical techniques to a model of respiratory syncytial virus (RSV), a widespread disease that can have severe consequences for small children and that exhibits extreme seasonality in locations around the world, including in Utah.