Forecasting the future risk of dengue epidemics facing climate change in New Caledonia, South Pacific.

BackgroundDengue dynamics result from the complex interaction between the virus, the host and the vector, all being under the influence of the environment. Several studies have explored the link between climate and dengue outbreaks in New Caledonia. None of them have explored the evolution of the dengue outbreak risk facing climate change. Methodology/Principal FindingsIn this study we chose the threshold time dependent reproduction number (Rt) as the modeling target to focus on time frames suitable for outbreak growths. A weekly statistical model of dengue outbreak risk (i.e. dengue outbreak probability) based on climate variables was developed using support vector machines (SVM) and then used in combination with CMIP5 projections of rainfall and temperature to estimate the future evolution of seasonal weekly risk and the inter-annual yearly risk of dengue outbreak up to the year 2100. The weekly risk of dengue outbreak is estimated using the number of days with maximal temperature exceeding 30.8{degrees}C during 80 days preceding the predicted week and the mean of precipitation during 60 days preceding the predicted week. According to the SVM model and to the worst greenhouse gas emission scenario projection (RCP8.5), the time frame suitable for epidemic growth will gain one month starting in November instead of December and the yearly risk of dengue outbreak occurrence increases regularly up to 2100 and reach a probability of 1 around 2080, making the dynamic of dengue fever endemic in New Caledonia. Conclusions/SignificanceA complete method to assess seasonal and inter annual variability of the risk of dengue outbreaks with respect to climate change is proposed. We conclude that climate change is likely to increase the risk of dengue in New-Caledonia (the other non climatic parameters remaining constant) in terms of both frequency of outbreak and temporal spread of the outbreak. Author summaryDengue virus is transmitted to human through the bite of an Aedes mosquito vector. Dengue fever is a worldwide public health concern, especially on tropical and subtropical countries. Over the last decade, the toll of dengue fever has increased in New Caledonia, raising questions about the future of the disease in this French island territory located in the South Pacific. Climate has a strong influence on dengue through its influence on the ecology of the vector and the viral cycle. Several studies have explored the link between climate and dengue in New Caledonia, with the aim of explaining and predicting dengue outbreaks. None of these studies have explored the possible outcome climate change will have on the risk of dengue fever in New Caledonia. This is the goal of this study, through projections of rainfall and temperature and the selection of an appropriate prediction target for our statistical model, we assess the climate-induced risk of dengue outbreaks up to the 2100 horizon. We prove that the inter-annual risk of dengue outbreaks in New Caledonia will raise, according to all the greenhouse gas emission scenarios and according to the high emission scenario, dengue fever will become an endemic disease in New Caledonia.