Research published this week in PLoS Medicine demonstrates associations between local rainfall and temperature and cases of dengue fever, which affects an estimated fifty million people per year worldwide. But the study finds little evidence that the El Niño-Southern Oscillation – the climate cycle that occurs every three to four years as a result of the warming of the oceans in the eastern Pacific – has a significant impact on the incidence of dengue in Mexico, Puerto Rico or Thailand.
Large outbreaks of dengue, a vector-borne viral disease spread by the Aedes aegypti mosquito, occur every few years in many tropical countries. Michael Johansson, of the Centers for Disease Control and Prevention in Puerto Rico, used a technique called “wavelet analysis” to probe relationships between the local climate, El Niño, and incidence of dengue in Mexico, Puerto Rico and Thailand — three countries where dengue is endemic. They were able to separate and compare seasonal and multiyear components of each. In all three countries temperature, rainfall, and dengue incidence varied strongly on an annual scale, showing association in the wavelet analysis.
