Using traditional spectral analysis and recently developed non-linear methods, we analyze
the incidence of six childhood diseases in Copenhagen, Denmark. In three cases, measles,
mumps, rubella, the dynamics suggest low dimensional chaos. Outbreaks of chicken pox, on
the other hand, conform to an annual cycle with noise superimposed. The remaining
diseases, pertussis and scarlet fever, remain problematic. The real epidemics are compared
with the output of a Monte Carlo analog of the SEIR model for childhood infections. For …