Regional-scale climate-variability synchrony of cholera epidemics in West Africa
1 Génétique et Evolution des Maladies Infectieuses, UMR CNRS/IRD 2724, 911 avenue Agropolis, BP 64501, 34394 Montpellier cedex 05, France
2 US ESPACE 140, IRD, 500 rue Jean-François Breton, 34093 Montpellier cedex 05, France
3 CNRS-UMR 7625, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris cedex 05, France
4 IRD, UR GEODES, 93143 Bondy, France
BMC Infectious Diseases 2007, 7:20 doi:10.1186/1471-2334-7-20Published: 19 March 2007
The relationship between cholera and climate was explored in Africa, the continent with the most reported cases, by analyzing monthly 20-year cholera time series for five coastal adjoining West African countries: Côte d'Ivoire, Ghana, Togo, Benin and Nigeria.
We used wavelet analyses and derived methods because these are useful mathematical tools to provide information on the evolution of the periodic component over time and allow quantification of non-stationary associations between time series.
The temporal variability of cholera incidence exhibits an interannual component, and a significant synchrony in cholera epidemics is highlighted at the end of the 1980's. This observed synchrony across countries, even if transient through time, is also coherent with both the local variability of rainfall and the global climate variability quantified by the Indian Oscillation Index.
Results of this study suggest that large and regional scale climate variability influence both the temporal dynamics and the spatial synchrony of cholera epidemics in human populations in the Gulf of Guinea, as has been described for two other tropical regions of the world, western South America and Bangladesh.