Chaos versus noisy periodicity: Alternative hypotheses for childhood epidemics

L. F. Olsen, W. M. Schaffer

Research output: Contribution to journalArticlepeer-review

236 Scopus citations


Whereas case rates for some childhood diseases (chickenpox) often vary according to an almost regular annual cycle, the incidence of more efficiently transmitted infections such as measles is more variable. Three hypotheses have been proposed to account for such fluctuations. (i) Irregular dynamics result from random shocks to systems with stable equilibria. (ii) The intrinsic dynamics correspond to biennial cycles that are subject to stochastic forcing. (iii) Aperiodic fluctuations are intrinsic to the epidemiology. Comparison of real world data and epidemiological models suggests that measles epidemics are inherently chaotic. Conversely, the extent to which chickenpox outbreaks approximate a yearly cycle depends inversely on the population size.

Original languageEnglish (US)
Pages (from-to)499-504
Number of pages6
Issue number4968
StatePublished - 1990

ASJC Scopus subject areas

  • General


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