1. Zoology Department, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
2. 501 ASI Building, Departments of Entomology and Biology, Penn State University, University Park, Pennsylvania 16802, USA

Correspondence to: B. T. Grenfell¹ Correspondence and requests for materials should be addressed to B.T.G. (e-mail: Email: b.t.grenfell@zoo.cam.ac.uk).

Abstract

Spatio-temporal travelling waves are striking manifestations of predator–prey and host–parasite dynamics. However, few systems are well enough documented both to detect repeated waves and to explain their interaction with spatio-temporal variations in population structure and demography. Here, we demonstrate recurrent epidemic travelling waves in an exhaustive spatio-temporal data set for measles in England and Wales. We use wavelet phase analysis, which allows for dynamical non-stationarity—a complication in interpreting spatio-temporal patterns in these and many other ecological time series. In the pre-vaccination era, conspicuous hierarchical waves of infection moved regionally from large cities to small towns; the introduction of measles vaccination restricted but did not eliminate this hierarchical contagion. A mechanistic stochastic model suggests a dynamical explanation for the waves—spread via infective 'sparks' from large 'core' cities to smaller 'satellite' towns. Thus, the spatial hierarchy of host population structure is a prerequisite for these infection waves.

1. Zoology Department, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
2. 501 ASI Building, Departments of Entomology and Biology, Penn State University, University Park, Pennsylvania 16802, USA

Correspondence to: B. T. Grenfell¹ Correspondence and requests for materials should be addressed to B.T.G. (e-mail: Email: b.t.grenfell@zoo.cam.ac.uk).