Impact of Climate Variability on the Incidence of Dengue in Mexico

Abstract

TM4-O-09 Introduction: Recent scientific evidence suggests that the climatic event known as El Niño/Southern Oscillation (ENSO) intensifies vector-borne disease. ENSO effects on dengue have not been elucidated; therefore, we evaluated the impact of climatic variations associated with this phenomenon on the incidence of dengue in 2 municipalities of the state of Veracruz, San Andrés Tuxtla, and Veracruz, Mexico during the period 1995 to 2003. Methods: We carried out a retrospective ecologic study with time-series analysis in which we compiled the cases of dengue reported weekly and the climatic parameters: temperature, rainfall, and surface sea temperature (SST), the latter as an ENOS indicator. Statistical models were developed using autoregressive integrated moving average models (ARIMA). The model's predictive ability was evaluated using data collected from 1995 to 2002, and it was validated with those observed for 2003. Results: Results showed that each degree Centigrade increase in sea surface temperature was associated with increased number of weekly cases of dengue by 46% (P = 0.001) and 42% (P = 0.002) with 16 weeks and 20 weeks delay in the municipalities of San Andrés Tuxtla and Veracruz, respectively. Increases in weekly minimum temperature and rainfall were also significant factors in the increase in reported cases of dengue. Comparing climate variables coefficients of each municipality, we found no significant differences. Discussion and Conclusions: This study demonstrates, with a series of weekly data, which include 2 ENSO events, that an increase in SST, minimum temperature, and precipitation is associated with an increase of dengue transmission cycles in costal municipalities of the Gulf of Mexico. The results and methods of this study may serve to develop an Early Warning System (EWS), which should be complemented with other variables that influence the transmission of the disease.