Simple Rules with Complex Dynamics

The incidence of infectious diseases such as measles shows patterns that oscillate between regular (occurring at a set time and location) and irregular cycles. In a Perspective, [May][1] discusses a report ([ Earn et al .][2]) that provides a simple mathematical model to explain the transitions between regular and irregular cycles of measles outbreaks in the United States and the United Kingdom. [1]: http://www.sciencemag.org/cgi/content/full/287/5453/601 [2]: http://www.sciencemag.org/cgi/content/short/287/5453/667