Complex demodulation: a novel time series method for analysing seasonal infectious diseases

Authors

  • Alexandra B Hogan The Australian National University http://orcid.org/0000-0002-6271-9921
  • Kathryn Glass The Australian National University
  • Robert S. Anderssen CSIRO Data61; The Australian National University; La Trobe University

DOI:

https://doi.org/10.21914/anziamj.v59i0.10894

Keywords:

seasonality, periodicity, infectious disease, epidemic, influenza, time series analysis.

Abstract

Understanding how seasonal patterns change from year to year is important for the management of infectious disease epidemics. Here, we present a mathematical formalization of the application of complex demodulation, which has previously only been applied in an exploratory manner in the context of infectious diseases. This method extracts the changing amplitude and phase from seasonal data, allowing comparisons between the size and timing of yearly epidemics. We first validate the method using synthetic data that displays the key features of epidemic data. In particular, we analyse both annual and biennial synthetic data, and explore the effect of delayed epidemics on the extracted amplitude and phase. We then demonstrate the usefulness of complex demodulation using national notification data for influenza in Australia. This method clearly highlights the higher number of notifications and the early peak of the influenza pandemic in 2009. We also identify that epidemics that peaked later than usual generally followed larger epidemics and involved fewer overall notifications. Our analysis establishes a role for complex demodulation in the study of seasonal epidemiological events. doi:10.1017/S1446181116000377

Published

2017-09-05

Issue

Section

Articles for Printed Issues