Host-pathogen time series data in wildlife support a transmission function between density and frequency dependence

Matthew J. Smith, Sandra Elizabeth Telfer, Eva R. Kallio, Sarah Burthe, Alex R. Cook, Xavier Lambin, Michael Begon

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

A key aim in epidemiology is to understand how pathogens spread within their host populations. Central to this is an elucidation of a pathogen's transmission dynamics. Mathematical models have generally assumed that either contact rate between hosts is linearly related to host density (density-dependent) or that contact rate is independent of density (frequency-dependent), but attempts to confirm either these or alternative transmission functions have been rare. Here, we fit infection equations to 6 years of data on cowpox virus infection ( a zoonotic pathogen) for 4 natural populations to investigate which of these transmission functions is best supported by the data. We utilize a simple reformulation of the traditional transmission equations that greatly aids the estimation of the relationship between density and host contact rate. Our results provide support for an infection rate that is a saturating function of host density. Moreover, we find strong support for seasonality in both the transmission coefficient and the relationship between host contact rate and host density, probably reflecting seasonal variations in social behavior and/or host susceptibility to infection. We find, too, that the identification of an appropriate loss term is a key component in inferring the transmission mechanism. Our study illustrates how time series data of the host-pathogen dynamics, especially of the number of susceptible individuals, can greatly facilitate the fitting of mechanistic disease models.

Original languageEnglish
Pages (from-to)7905-7909
Number of pages5
JournalPNAS
Volume106
Issue number19
Early online date23 Apr 2009
DOIs
Publication statusPublished - 12 May 2009

Keywords

  • cowpox
  • disease
  • population cycles
  • Markov chain Monte Carlo
  • MICROTUS-AGRESTIS
  • INFECTIOUS-DISEASES
  • COWPOX VIRUS
  • FIELD VOLE
  • POPULATION BIOLOGY
  • DYNAMICS
  • OUTBREAK
  • MODELS
  • MEASLES

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