Cyclic epidemics and extreme outbreaks induced by hydro-climatic variability and memory

Milad Hooshyar, Caroline E. Wagner, Rachel E. Baker, C. Jessica E. Metcalf, Bryan T. Grenfell, Amilcare Porporato

Research output: Contribution to journalArticlepeer-review


A minimalist model of ecohydrologic dynamics is coupled to the well-known susceptible-infected-recovered epidemiological model to explore hydro-climatic controls on infection dynamics and extreme outbreaks. The resulting HYSIR model reveals the existence of a noise-induced bifurcation producing oscillations in infection dynamics. Linearization of the governing equations allows for an analytic expression for the periodicity of infections in terms of both epidemiological (e.g. transmission and recovery rate) and hydrologic (i.e. soil moisture decay rate or memory) parameters. Numerical simulations of the full stochastic, nonlinear system show extreme outbreaks in response to particular combinations of hydro-climatic conditions, neither of which is extreme per se, rather than a single major climatic event. These combinations depend on the assumed functional relationship between the hydrologic variables and the transmission rate. Our results emphasize the importance of hydro-climatic history and system memory in evaluating the risk of severe outbreaks.

Original languageEnglish (US)
Pages (from-to)20200521
Number of pages1
JournalJournal of the Royal Society, Interface
Issue number171
StatePublished - Oct 1 2020

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Biophysics
  • Bioengineering
  • Biomaterials
  • Biochemistry
  • Biomedical Engineering


  • dengue
  • epidemiology
  • hydrology
  • infectious disease

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