title: A non-stationary relationship between global climate phenomena and human plague incidence in Madagascar.
abstract: BACKGROUND
  Plague, a zoonosis caused by Yersinia pestis, is found in Asia and the Americas, but predominantly in Africa, with the island of Madagascar reporting almost one third of human cases worldwide. Plague's occurrence is affected by local climate factors which in turn are influenced by large-scale climate phenomena such as the El Niño Southern Oscillation (ENSO). The effects of ENSO on regional climate are often enhanced or reduced by a second large-scale climate phenomenon, the Indian Ocean Dipole (IOD). It is known that ENSO and the IOD interact as drivers of disease. Yet the impacts of these phenomena in driving plague dynamics via their effect on regional climate, and specifically contributing to the foci of transmission on Madagascar, are unknown. Here we present the first analysis of the effects of ENSO and IOD on plague in Madagascar.
  
  
  RESULTS
  We use a forty-eight year monthly time-series of reported human plague cases from 1960 to 2008. Using wavelet analysis, we show that over the last fifty years there have been complex non-stationary associations between ENSO/IOD and the dynamics of plague in Madagascar. We demonstrate that ENSO and IOD influence temperature in Madagascar and that temperature and plague cycles are associated. The effects on plague appear to be mediated more by temperature, but precipitation also undoubtedly influences plague in Madagascar. Our results confirm a relationship between plague anomalies and an increase in the intensity of ENSO events and precipitation.
  
  
  CONCLUSIONS
  This work widens the understanding of how climate factors acting over different temporal scales can combine to drive local disease dynamics. Given the association of increasing ENSO strength and plague anomalies in Madagascar it may in future be possible to forecast plague outbreaks in Madagascar. The study gives insight into the complex and changing relationship between climate factors and plague in Madagascar.
authors.affiliation: LUCINDA group, Institute of Infection and Global Health, Department of Epidemiology and Population Health, University of Liverpool, Neston, United Kingdom.
authors.forename: Katharina S
authors.initials: KS
authors.lastname: Kreppel
authors.affiliation: LUCINDA group, Institute of Infection and Global Health, Department of Epidemiology and Population Health, University of Liverpool, Neston, United Kingdom; Department of Geography and Planning, School of Environmental Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Cyril
authors.initials: C
authors.lastname: Caminade
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Sandra
authors.initials: S
authors.lastname: Telfer
authors.affiliation: Unité Peste - Institut Pasteur de Madagascar, Antananarivo, Madagascar.
authors.forename: Minoarison
authors.initials: M
authors.lastname: Rajerison
authors.affiliation: Centers for Disease Control and Prevention, Division of Bacterial Diseases, Atlanta, Georgia, United States of America.
authors.forename: Lila
authors.initials: L
authors.lastname: Rahalison
authors.affiliation: Department of Geography and Planning, School of Environmental Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Andy
authors.initials: A
authors.lastname: Morse
authors.affiliation: LUCINDA group, Institute of Infection and Global Health, Department of Epidemiology and Population Health, University of Liverpool, Neston, United Kingdom; Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Neston, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Baylis
mesh_terms: D002980:Climate; D059000:El Nino-Southern Oscillation; D006801:Humans; D015994:Incidence; D008270:Madagascar / Q000453:epidemiology; D010930:Plague / Q000453:epidemiology*; D012621:Seasons