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

Area of Science:

• Ecohydrology
• Epidemiology
• Infectious disease dynamics

Background:

• Epidemiological models often overlook environmental influences.
• Hydro-climatic factors significantly impact disease transmission and outbreak patterns.

Purpose of the Study:

• To investigate the influence of ecohydrologic dynamics on infection patterns.
• To develop a coupled model for exploring hydro-climatic controls on disease outbreaks.

Main Methods:

• Coupling a minimalist ecohydrologic model with the susceptible-infected-recovered (SIR) epidemiological model.
• Developing the Hydro-eco-SIR (HYSIR) model.
• Employing linearization for analytic expressions and numerical simulations for nonlinear analysis.

Main Results:

• The HYSIR model demonstrates a noise-induced bifurcation leading to oscillations in infection dynamics.
• An analytic expression for infection periodicity was derived, incorporating epidemiological and hydrologic parameters.
• Extreme outbreaks result from specific combinations of hydro-climatic conditions and system memory, not single extreme events.

Conclusions:

• Hydro-climatic history and system memory are critical for assessing severe outbreak risks.
• The study highlights the complex interplay between environmental conditions and infectious disease dynamics.
• Understanding these linkages is crucial for effective public health interventions and forecasting.