Complex multiannual cycles of Mycoplasma pneumoniae: Persistence and the role of stochasticity
Bjarke Frost Nielsen, Biocomplexity Group, Niels Bohr Institute, Copenhagen
Up-front summary for the impatient: I will talk about a recent paper[*] (with Mogens and others!) where we use dynamical systems and stochastic processes methods to understand some mysterious oscillations in the prevalence of a bacterial disease.
The longer version: The bacterial pathogen Mycoplasma pneumoniae exhibits unusual, complex multi-year cycles, with a period of ~5 years. The origins of these cycles have long been debated, and more or less complicated explanations have been proposed.
By fitting a mechanistic mathematical model to data from Denmark spanning several decades, we find a parsimonious explanation for the persistent 5yr periodicity, in the form of quasicycles. A deterministic model explains the periodicity and shape of the cycles, while environmental randomness - such as variability in host contact patterns - is needed to sustain them. The temporary disappearance of cycles during 1979 to 1985 is explained as a consequence of stochastic mode-hopping. The work has practical implications for predicting the epidemiological dynamics of M. pneumoniae across diverse settings and suggests that noise-induced dynamics should be considered as a potential driver of complex cycles in other endemic pathogens.